Category Archives: Botany

Latitudinal Diversity: my theory

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Growing up in England I was fond of woods, but when I went to live in a cloud forest (which is a tropical rainforest in the mountains) in central America, three things stood out as massively different to the forests I knew in England.

  1. There was a huge variety of plants. In the UK, most woods have the same few trees and plants repeated – oaks, birches, sycamores and ash for the trees; bracken and brambles at ground level. In the cloud forest, almost no tree or ground level plant was repeated, to put it technically, it had a greater species diversity.
  2. The ecosystem was far more interactive than I was used to. Trees were laden with epiphytes, and there was barely a leaf without fungus, insects or a virus. It seemed that almost every plant surface had something else growing on it. In the UK, there are only occasional galls and nests, the odd bit of moss, and epiphytic plants are rare.
  3. The variety in colour, shape and habit of the cloud forest plants was huge, at every turn I uncovered new leaf shapes and colours, whereas in the UK there are mostly green leaves growing in a few different patterns. (Note that I am talking about native woods in the UK here, we import many different garden plants from other countries and those have a greater variety of shapes and colours)

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The differences were so immense and fascinating, I started researching as soon as I was able to.

What I discovered is that there is higher diversity of species and greater number of species (species richness) the closer to the equator you get. This is known as the latitudinal diversity gradient.

Science hasn’t quite explained it yet, but there are theories, I also have my own which I want to share. I’ve not come across anyone suggesting the same explanation, although the chances someone has, somewhere.

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An aroid flower in Ecuador

The Facts

  • The greatest number of species for the major taxa – flowering plants, ferns, mammals, birds, reptiles, fresh water fish, amphibians, insects and snails – are in the tropics.
  • Species diversity and richness increase as you travel towards the equator.

For example: The 1950s doc ‘Evolution in the Tropics’ by Dobzhansky stated that Greenland had 56 species of birds, New York 195, Guatemala 469, Panama 1100 and Colombia 1395.

  • While tropical moist forests have the greatest diversity, even tropical savannahs and grasslands are more diverse than similar landscapes in temperate areas. This is especially important, because it suggests that the difference is not just due to terrain, but also latitude.
  • Recent research suggests that there are more fungi species in the tropics too. There isn’t enough known about diversity of bacteria species across the globe.
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A pink-leaved climber growing within a green-leaved plant.

The Theories

There are a number of theories. They include factors such as the Ice Age, which affected the poles greatly and the tropics less so; the size of the tropics compared to other areas; and the higher levels of predation so that the fight to survive drives evolution. All of the theories are contested, a few can explain part of the difference, but not all. Some are circular, eg. there is greater species diversity, because there are more competitors for food sources.

For more detail try A Neotropical Companion by Kricher (where much of my info comes from) or Wikipedia which has a number of other theories too.

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My Theory – it’s all about the small things

One notable difference about the equator is that there is little change in light and temperature. Where as in the UK the nights are very long in the winter and short in the summer, in Central America it gets dark at 5pm all year round. Temperatures are also more stable; slightly closer to the poles, the more temperatures can fluctuate from minus degrees in the winter to scorching heat in the summer. In the tropics, it’s pretty much hot all year round – or in high up cloud forests it’s consistently warm.

This lack of change makes some difference to larger animals and plants since they don’t need to go into dormancy they can grow and reproduce all year round. But their life cycles are still fairly slow, reproducing once a year or every few years. However, this difference is far more significant when it comes to very small organisms because their lifecycles are so much shorter, and they are more affected by changes in temperature and light. Those quick lifecycles mean they can mutate, adapt and evolve at far greater rates too.

So I believe that is why there is greater species richness, abundance and diversity of small organisms at the equator, but the difference is not so pronounced in larger organisms, so what else is a factor?

I believe that it is the species diversity of smaller organisms that directly causes the diversity in larger organisms through parasitism and symbiosis. Parasitism drives evolution and symbiosis aids survival.

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First, some terminology

Parasitism

Parasites are usually insects, fungi, small plants or bacteria and are harmful to larger plants and animals, taking what they need without concern for the host. Organisms often evolve to protect themselves from threat. Parasites are a threat. The more threats, and the more varied the threats, the more animals and plants need to evolve to fight them. This is a common, but as yet unproved theory.

For example: If a plant has a mutation of hairy leaves that deter insects, then in an environment with many insects, that mutation is more likely to lead to the survival of that plant and the proliferation of the hairy-leaf gene.

Symbiosis

Symbiosis between insects and fungi?

Symbiosis

Symbiotic relationships tend to drive specialisation and help organisms to survive. Because the rainforest is so crowded, there is a constant battle for nutrients, space and light, so forming an alliance is beneficial. Through the generations, that alliance tends to become tighter and more exclusive. Symbiosis can be seen between many animals, plants, fungi and bacteria.

For example:  Ants forming a protective army inside an acacia tree and fighting off any animal that comes to eat it. Or aroid flowers that are only pollinated by one type of fly, so they evolve to give off a scent that attracts that specific fly (often rotting meat). In a crowded rainforest, if all plants targeted all insects, then many plants would get missed and never pollinated. Forming a symbiotic relationship is like putting an address on a letter, instead of flinging up in the air and hoping someone reads it.

The Small Things

Fungi

Fungus in Ecuador

The ideal conditions for fungi to grow are warm moist ones. In the UK fungi live in the ground unseen, all year round. Then in autumn they produce fruiting bodies – ie the mushrooms that enable them to reproduce – that’s because the soil has warmed over the summer and there’s plenty of rain. In the tropics, the soil never cools, and humidity is constant, this means the reproductive phase can also continue all year round.

 

 

 

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Why fungi are important to larger organisms – fungi can be both beneficial and harmful to plants. Some fungi form a symbiotic relationship with them, growing on their roots and enabling them to take in nutrients that the plants would struggle to access on their own – these are known as mycorrhizal fungi. This harmoniuos relationship can take centuries to form. This is one reason why it’s so difficult to regrow plants on an area that has been de-forested, because the mycorrhizal fungi are no longer there, and the plants can’t access nutrients without them.

Fungi can also be parasitic and break down healthy wood. That’s what fungus does essentially, breaks stuff down, it’s a decomposer – that’s good when it’s breaking down dead matter to release the nutrients, but bad when it breaks down living material.

Bacteria

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Either bacteria or insect galls

Like fungus, the ideal conditions for bacteria to grow is warmth and moisture, they are also sensitive to light changes. So, the equator, and especially the rainforest at the equator, has perfect conditions.

Why is bacteria important to larger organisms – like fungi, bacteria can be both good and bad for plants. Some bacteria work in a similar way to fungi, attaching to roots and breaking down nutrients (specifically nitrogen) into a form the plants can absorb. And, like fungi, bacteria can be harmful, causing diseases.

Insects

 

 

 

Insects also like warmth and wet. We know in the UK if there is a warm summer followed by a lot of rain, then the insects will increase. In the tropics, those are the constant conditions. Even in drier areas, the consistency of temperature is enough to maintain insect populations.

Why insects are important to larger organisms – insects can also be a blessing or a burden to plants. Leaf cutter ants will ravage a tree, defoliating it, but as described above, ants can protect trees too. The photo above shows a number of insect galls on plants, where parasitic insects alter how a plant grows to create their habitats.

 

 

 

 

 

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Conclusion

To put it simply…

According to my theory,

  • Smaller organisms thrive in stable environments where light and temperatures are fairly constant all year round.
  • The resulting high numbers and quick life cycle leads to greater opportunities for them to mutate and evolve.
  • Smaller organisms affect the number and diversity of larger organisms through parasitism and symbiosis.
  • Parasitism drives species richness, by forcing larger organisms to evolve to survive. Symbiosis aids survival and promotes specialisation.
  • So the numbers and diversity of larger organisms increases.

 

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Mosses and lichen on a branch

 

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Why don’t we ban Glyphosate? (Round Up)

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Abandoned station as the plants reclaim…

There’s been a lot of publicity surrounding the herbicide Glyphosate, the main ingredient in Round Up. A recent court case determined that it can cause cancer. It has also been found in streams and some water supplies. The media have been vocal in the dangers of this terrible chemical, and people must be wondering: why hasn’t it been banned?

The problem is, there is pretty much no other effective herbicide to use.

As someone who’s worked for a number of gardening companies and in a number of large gardens, it’s been the only non-selective herbicide I’ve come across (non-selective means it kills all plants). However, I was aware a number of countries had banned it, so I was convinced there must be something else to use. It’s been bugging me for a while, so thought I’d do a bit of investigating.

Why Do We Need a Herbicide Anyway?

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Plants can grow anywhere

Naturally, when most people think about banning herbicides, they worry about the patios and paths in their gardens, but it’s a little more serious than that. It’s not surprising people think of plants as mostly well-behaved organisms, because that is how we keep them, manicured and contained. But plants have been colonising land since long before animals ever did, and they’re very good at it. If all humans suddenly vanished, it would only be a few years before plants had made headway in reclaiming roads and buildings.

Many plants don’t need a nice flowerbed in order to grow, plenty don’t need soil at all.

How plants take over a hostile space

First moss and liverworts grow on bare rock, then when they die their decomposing leaves provide a little bit of soil for slightly bigger plants, which have more tenacious roots that ease into cracks. Then they die and create more soil. Soon there is enough soil for plants with tougher roots to sprout, and the cracks widen further. Once there’s a perfect environment for invasive weeds to take hold, it can be only a few months before waist high clumps are sprouting up in great numbers. And this can happen anywhere, on railway tracks, pavements, roads, even through walls.

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Buddleia growing in railway arch walls

When it comes to invasive weeds, Buddleia (Buddleia davidii) and Japanese knotweed (Fallopia japonica) are the biggest problems, and a problem that only Glyphosate solves. Whereas plants such as Himalayan Balsam (Impatiens grandulifera) and Skunk Cabbage (Lysichiton americanus) tend to be confined to wet areas, Buddleia and knotweed can and do grow anywhere. Buddleia can grow in walls, knotweed can break through concrete. These plants are kept in check by Glyphosate, and whole companies exist to remove them. I studied for my spray certficate with a couple of guys whose sole job it was to inject Japanese Knotweed with Glyphosate. Without chemical intervention, these tough innovative plants would take over, and soon they would affect the running of trains, and damage buildings and roads. Pulling them out acheives little. Pull Buddleia out of a wall and you’ll damage the wall. Pull knotweed out of the ground and you’ll cause more shoots to sprout in their place like a Hydra from Greek mythology. A solution needs to be tough.

How Have Countries Banned Glyphosate?

Whenever trouble with Glyphosate raises its head, the media talks of countries which have banned it, so why can’t we? Looking deeper into this leads to some interesting caveats to the bans. Although 14 countries are reported as having bans, few have an outright ban.

Some countries, such as Belgium and the Netherlands have restricted use (only for commercial use or to treat invasive weeds). Some are undergoing the slow process to find alternatives and intend a ban in a few years time (eg France). Bermuda started out with an outright ban, then relaxed the laws. Canada has banned it except in the case of invasive weeds.

A number of countries such as Saudi Arabia, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates have an outright ban. I haven’t been able to find out why, but maybe there is a large lower-wage workforce there, who will do the weeding by hand. There are certainly invasive weeds in the Middle East, although many are dependent on irrigation provided by humans, so that may be  a factor. (If anyone knows the reason, please email me at the address at the bottom of this blog and I’ll update).

Despite headlines calling for a ban, it looks like the solution is more complicated.

What are the alternatives?

Salt – this is often cited, however, Sodium Chlorate, a derivative of salt used as a herbicide, is banned in Europe. Using it on a few weeds in one garden isn’t such a big deal, but using large amounts on train tracks could be an environmental disaster. It depletes the ozone layer and is harmful to aquatic life. It’s also toxic to humans.

Vinegarwas used in Bristol to control weeds for a year. It was found to be not cost effective and not have such a long-lasting effect as Glyphosate. Personally, I’d be concerned at the environmental effect of throwing large quantities of vinegar around. Large quantities of anything that kills plants can cause environmental harm.

Handweeding – this is incredibly slow and isn’t practical on a large scale. It would mean shutting down roads and train tracks and new purpose-built machinery and a lot of cheap labour. Fine for private gardens though.

Mulching – useful in flower beds, but useless on paths and patios and won’t stop plants that grow out of walls or through buildings.

Steam weeding (sometimes called Heat Weeding) – this involves a machine that sprays out water at 99 degrees. I’ve used one, it is effective, although still in its infancy, so the machine is cumbersome and not very versatile yet. It’s being trialled mainly in Australia and Sweden. Given time, it’s one of the best options and there needs to be investment, plus government incentives to use it.

Fire – not setting fire to the weeds, but running a flame over them. Another good possibility. Not something I’ve used, but I can see how it would work on open ground. I don’t know the logistics of using it on buildings, but it’s a possible solution.

And Finally…

I’m concerned that this blog may come across like I’m resigned to chemical use and I really don’t want that. This is a beautiful world, we’ve been messing with it for a long time and we’re starting to feel the terrible consequences of that. So it’s time to grow up as a species and start taking better care of our surroundings. One way to do that is to reduce chemical use and work with nature in a sustainable and less intensive way. There will be ways to reduce and eventually get rid of Glyphosate, but in order to do that, we need to accept it’s not just a matter of banning one chemical and then moving onto another.

If anyone has any knowledge or ideas to add to this, then drop me a line at therealtetrapod at gmail dot com. Thank you!

Mendoza Glyphosate

Another picture of Mendoza station, just because…

 

How to Make a Rainbow Rose

My first thought on seeing one of these was, how do they do that? Well, I think I’ve figured it out…

Rainbow rose

Picture credit: my mum

 

I bought a rainbow rose for my mum on Mother’s Day, I guessed she’d be as curious as me to know how they make them. After having a think and looking at the base of the stem it became clear.

A normal, wrong-coloured rose is created by simply putting the end of the stem in food colouring (mixed with water), the plant then sucks it up as it would normal water, and the colour spreads throughout the stem, leaves and flowers.

Lengthways section through a rainbow rose

Lengthways section through a flower stem

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Cross section through a flower stem showing different colours inject into the xylem

For a mutli-coloured rose it takes more precision, but the idea is the same. A different coloured dye is injected into each of the xylem tubes, these are around the edge of the stem and take water through the plant. Because the xylem tubes stretch from one end of the plant to the other, and do not merge, the food colouring remains separate, all the way to the petals, so that each petal is flooded with a different colour.

The evidence for this is small dots of colour around the edge of the cut stem, where the dye was injected in.

Schachen Alpine Garden

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Schachen Landscape

Open four months of the year and accessible only on foot, the Schachen Alpine Garden contains plants from all over the world. As can be seen in the photos, Schachen is often foggy, and despite being surrounded by the Alps, we barely saw them.

Alpine plants have a few conditions in common no matter where they are from; they have to cope with extreme cold (Schachen is often covered with snow), a short growing season, high winds, and a lack of rain. Alpine plants are mostly small and low growing, this enables them to flower in the short time when the conditions are favourable and keep below the high winds.

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Anthyllis vulneraria

 

A number of plants had an ability to repel water and hold it in droplets above the leaves, I think this is a way of protecting them when covered in snow, stopping the leaves from being damaged. (see photos below)

Due to the mix of rock types on the mountain, the soil is very varied, with alkaline and acid soils side by side. This means that acid loving and alkaline loving plants that would never normally grow together, do. For example, this wild Clematis alpina (alkaline) and pine tree (acid). (see below)

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Clematis alpina growing on a pine

Many of the pine trees on the mountain are growing right out of the rock (see photos below). In autumn animals bury seeds in the rock to serve as food stores for the winter. Many of these seeds are forgotten, and then germinate.

The photo below is of an unusually shaped Campanula, nothing like the normal bell-shaped flower. Because of its shape it is known as devil’s claw.

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Devil’s Claw Campanula

Cows feed on the vegetation on the mountain. As it gets warmer, and the cows eat all the vegetation lower down, they are moved up higher. This can cause problems, because the cows will eat almost everything but Rheum (a genus containing rhubarb) because it is poisonous. As a result, the Rheum starts to take over, so there is a problem with this turning the mountain landscape into a monoculture. Rheum is the large-leaved plant in the photo below.

Mosses and lichens were in abundance in Schachen.

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Lichen growing on pine tree

Wild orchids grew on the mountain also.

My favourite two photos from the trip:

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Thistle flower

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Red spotted bug

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Schachen Alpine Garden

 

 

Plant Families: Araceae (aka Aroids or Arums)

Zantedeschia Inflorescence

Zantedeschia Inflorescence

A Few Basic Facts

  • Aroids are monocots in the family Araceae (aka arum family), in the order Alismatales. Most other families in this order contain tropical or aquatic plants, eg Hydrocharis and Saggitaria.
  • Araceae has 104-107 genera. The largest genus is Anthurium with over 700 species.
  • Location: Latin American tropical regions have the greatest diversity of aroids, however, they can also be found in Asia and Europe. Australia has only one endemic species – Gymnostachys.
  • Habitat: Aroids can be aquatic (water), epiphytic (air) and terrestrial (ground). Most are tropical, but there are also arid and cold loving aroids.
  • Distinctive features: All have an inflorescence (a structure containing a group of smaller flowers) which consists of a spadix (always) and a spathe (sometimes).
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Aroid Flowers

  • Aroids can be hermaphrodite (each flower is both male and female), monoecious (male and female flowers on the same spadix) or dioecious (male and female flowers on completely different plants).
  • This family contains one of the largest flowers (Amorphophallus titanium, the titan arum) and the smallest (Wolffia, duckweed).
  • Some aroid leaf and inflorescence shapes:
Aroid Leaf Shapes

Aroid Leaf Shapes

Leaves

Aroid Leaves

Fruits

Aroid Fruits

Adaptations

Like many tropical families, aroids have evolved a number of adaptations to stay healthy and propagate. Some examples of adaptation:

  • The spathe protects the flowers and in some cases is used to trap insects for pollination. It is not a petal, but a modified leaf. Many spathes turn green and photosynthesize after flowering has finished.
  • Aroids have different types of roots adapted to their purpose. They have different adventitious roots  for climbing, attaching to rocks or taking in water.
  • Many tropical species have shiny leaves to deter the mosses and lichens that grow in abundance in the rainforest.
  • Smell is used by many species to attract pollinators. The smell of rotting meat, fungi and excrement is used for flies and beetles. Fragrant scents are used to attract bees.
  • In many species the spadix actually heats up and can reach 25°C, even in near freezing conditions. This increases the release of smells to attract pollinators. The heat also makes visiting insects more active.
  • Aroids that want to attract flies and beetles often have a warty, hairy, twisted appearance, with dark colours. This is to mimic the effect of dead animals, fungi or excrement.
  • In some species, leaves may change shape from juvenility to adulthood – changing from variegated to unvariegated, pale red to green, or altering the number of lobes of the leaf. Colour change may deter animals from feasting on the fresh young leaves by making them look less leaf-like.
  • Most species in Araceae have tubers or rhizomes, this means a damaged plant has the food storage and ability to grow new shoots from many points beneath the ground. Some aroids have other means of vegetatively propagating themselves, such as bubils and offsets.
  • A number of aroids are poisonous, some are edible. Aroids have evolved poisons in some species as protection. Those that are edible did not evolve to be eaten by us, rather we have evolved to be able to eat certain plants.

Reproduction

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Male and Female Flowers

Because many aroids are monoecious there is a danger of self-pollination. While self-pollination is easy (a guaranteed fertilisation), it leads to less genetic variety and less ability to adapt to changes in the environment. Aroids are particularly variable plants, in one small area of the Thai Peninsula 22 distinct varieties of the plant Aglaonaemia nitidum f. curtisii were found. However, in order to achieve this variation, the plant needs to cross pollinate reliably. It does this by being protogynous, meaning the female flowers on an inflorescence ripen first and then later male flowers produce pollen.

The Generic Process for Monoecious Aroids

A beetle, fly or bee (hopefully covered in pollen) is attracted by the scent given off by the heated spadix. The insect flies around inside the spathe, lands on the slippery surface and falls into the gap between the spadix and spathe. At this point only the female flowers are mature, and the  insect, made more active by heat from the spadix, moves about bumping into the flowers and depositing the pollen. Now, the insect has fulfilled the first part of its function, the aroid would like it to pick up pollen from the male flowers. However, the male flowers will not ripen for a day or so yet, so the insect needs to be held hostage. The slippery spathe ensures that the insect can’t escape, it is given sustenance in the form of nectar. Once the male flowers are ready and producing pollen, the slippery surface of the spathe breaks down, allowing the insect to escape. As it flies away it bumps into the male flowers, picking up more pollen to take to the next plant of the same species that it comes to.

Two Specific Examples of Monoecious Reproduction

Philodendron auminatissimum: Sometimes the pollinating insect can outstay its welcome, perhaps damaging flowers or laying eggs. This Philodendron has overcome the problem by shrinking the spathe after the male flowers have become active. This means that the beetle must leave or become crushed.

Arum nigrum: This arum doesn’t trap visiting flies, it merely confuses them. The hood of the spathe hangs over the spadix, obscuring the  sunlight, and there are translucent marking in the base of the spathe. When a visiting fly tries to escape, it heads for the light, but this just guides it deeper into the spathe. This leads to panicked and more active movement, ensuring pollination.

Arum nigrum

Arum nigrum

Reproduction in Other Aroids

In dioecious aroids the female flowers are found on a different plant to the male flowers, so a genetic mix is guaranteed. Not many aroids are dioecious, but a few species of Arisaema are.

A few aroids are even paradioecious and change gender to suit circumstances.

Hermaphrodite aroids are similar to monoecious ones, the male and female parts on each flower mature at different times so self pollination cannot occur.

Habitat

Arid

For the most part, arid aroids have not evolved the typical shrunken leaves and thickened cuticle of other desert plants. Instead they tend to grow under trees and bushes and at the base of rocks where a damp, shady microclimate allows them to survive. They have unusually lush foliage for arid plants. This would make them a target for being eaten, but they have dealt with this by producing harsh toxins and needles of calcium oxalate that pierce and poison the throats of animals. Animals know to stay well clear of aroids.

Some Examples

Dead Horse Arum

Heliocodicerous muscivorus

Heliocodicerous muscivorus: This is called the dead horse arum. It has an inflorescence 35cm long and wide. It grows in the shelter of rocks on a few islands on the Mediterranean. It is pollinated by either flies or beetles and grows where sea birds have their colonies at nesting time. Sea birds live in a mess of rotting fish and eggs, dead chicks and excrement, which attracts the flies/beetles. The arum must then compete with the smell of these, in order to attract those same insects for pollination. It mimics the dead not only in smell, but also by looking like the corpse of part of a horse, complete with tail. Visiting insects find themselves falling into where the ‘tail’ is and becoming trapped by the slippery walls. Many insects lay their eggs inside, although any maggots that hatch will likely starve to death. The insects are held for two to three days and are fed by nectar.

Note: It’s worth looking at photos of the dead horse arum, my painting doesn’t really do it justice.

Sauromatum venosum: This is the called the voodoo lily because it has the ability to flower without soil or water, using only the energy stored as starch in the corm. It smells rotten.

Stylochaeton lancifolius: This aroid has flowers and fruits half buried in the ground. I have been unable to find information about why this is. My suspicions are:

  1.  It is pollinated by animals that are close to the ground. This can be seen in Aspidistra flowers, pollinated by slugs and snails. The flowers grow on the ground, under the leaves.
  2. Being submerged provides a little protection, even if eaten or stepped on, the Stylochaeton still has half a flower remaining.
  3. The fruits are eaten by something small. Having eaten the fruit, the seeds can be dispersed in the faeces.
Stylochaeton lancifolia

Stylochaeton lancifolia

Tropical

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Rainforests are dense, shady, and teeming with aggressive life. Animals, plants, fungi and bacteria are locked in a constant arms race. Consequently aroids have developed strong poisons, shiny leaves and the ability to climb to cope with some of these problems. In the tropics, latitudinal diversity (a wider variety of organisms that occurs close to the equator) means that it may be many miles through dense forest between plants of the same species. For this reason, aroids use very strong, and often unpleasant, smells to attract the right kind of insect.

A tropical rainforest has distinct layers and aroids grow in each of these. There are terrestrial aroids growing in the ground and epiphytic ones that climb into the canopy.

Climbers and epiphytes have only aerial, adventitious roots. There are two types: those that are sensitive to light and make for dark crevices where they can grip, and those that are sensitive to gravity and hang down from the plant in order to soak up rain and humidity.

Terrestrial Examples

Deiffenbachia grows in the Americas, while Aglaonema is native to Asia, they are both highly variable, but virtually indistinguishable from one another. This is an example of convergent evolution. Both contain toxins as a defence; Deiffenbachia is commonly known as dumb cane, because the if eaten, it causes the throat to swell, so that speech is impossible.

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Aglaonema and Deiffenbachia – both highly variable, but in similar ways

 

Amorphophallus: This is a genus of tropical and subtropical aroids, native to Asia, Africa and Australasia. They attract flies and beetles by giving off the smell of rotting meat. Unusually, Amorphophallus species only put out one leaf or one inflorescence at a time, one a year. The single leaf is highly divided.

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Some Amorphophallus inflorescences

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Single, highly divided leaf of Amorphophallus

Some species in this genus also have white patches on the stem, these are to mimic lichen growing on trees and serve to protect them from stampeding elephants. When tramping through the jungle elephants have learnt to avoid trees, which are usually covered in lichen. Amorphophallus would be very easily damaged by an elephant, so by looking a bit more like a tree they can fool the elephant into avoiding them.

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Lichen mimicking stem

Epiphytic Examples

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Monstera

Monstera: These are one of the few plants to have holes in their leaves. Recent research shows that leaves with holes benefit in shady areas because the light coming through the trees is often dappled. By having holes in their leaves, Monstera cover a larger area with the same amount of leaf (so the same amount of energy used to make it) as a smaller leaf without holes. This allows the plant to take advantage of any sunlight that gets through the canopy.

Anthurium punctatum: This is an aroid from Ecuador. It has formed a symbiotic relationship with ants. It has nectaries away from the flowers because it is not trying to attract pollinators, but protectors. The ants set up home in the Anthurium and guard it from animals and insects that may eat it. However, in this Anthurium the ants are particularly aggressive and keep away pollinators also. The ants also secrete an antibiotic substance called myrmiacin, which is antibiotic and protects the ants from moulds and bacteria that might cause disease. However, this substance prevents pollen tube formation needed for the plant to be fertilised. These two barriers to pollination mean that the species can only propagate itself vegetatively.

Philodendron: This is a diverse genus. Plants can be epiphytic, hemiephytic or (occasionally) terrestrial. Hemiepiphytic means that the plant spends part of its life-cycle as an epiphyte (in the air). It may start off on the ground and then wind its way up a tree, then let its original roots die back. Or it may start as a seedling in the branches of a tree and a root will trail its way to the ground.

Philodendron bipinnatifidum

Philodendron bipinnatifidum

Temperate Woodland

Arisarum proboscideum

Arisarum proboscideum

Arisarum proboscideum: aka the mouse plant. This is a woodland aroid, native to Spain and Italy. It has flowers like little mice. The ‘tails’ of these give off a mushroomy odor, that attract fungus gnats for pollination. The flowers have a spongy white appendage inside the spadix that looks like a mushroom to complete the deception. Fungus gnats often lay their eggs in the flowers, although the maggots won’t live to adulthood.

Aquatic

As I have blogged before, plants never evolved much in water. This means that all aquatic plants have evolved on land and then evolved again to cope with life in water. Some problems faced are – damage to flowers and leaves due to water currents, lack of access to pollinators, water blocking out light, lack of oxygen (leading to rotting roots), and the heaviness of water (800 times as dense as air) putting pressure on foliage.

Some solutions to problems:

  • Aerenchyma:  these are gas filled cavities that improve buoyancy and oxygenation.
  • Fish shaped foliage: these offer less resistance to water currents, so less damage occurs.
  • Larger surface area in relation to volume: ie filmy leaves. This increases photosynthesis  eg Cryptocoryne
  • Roots: These are not needed to transport water, since it can be taken in by all parts of the plant. However, roots are used to anchor the plant and stopped it being carried away by currents. eg Jasarum steyermarkii
  • Reproduction: Many aquatic aroids find it easier to spread vegetatively rather than by flowering, in order to avoid flowering problems.

An Example

Pistia stratiotes 2.JPG

Pistia stratiotes: This is the only floating aquatic aroid, growing in swampy deltas in India and West Africa. It is adapted to staying still in fast moving currents, and has found the balance between sinking and blowing away.  The inner tissues have aerenchyma and the outer surfaces are ridged, velvety and with dense covering of hairs. This makes it unable to sink, and water repellent. Feathery roots act as an anchor. It has tiny flowers in a protective hairy spathe.

Pistias form a dense mat on the surface of the water, and can create mats of 15m wide. This makes Pistia something of a weed, causing problems to the ecosystem because the water underneath is deprived of light.

However, Pistia is not only harmful, some ecological benefits:

  • The darkness caused by the Pistia mats has led to the evolution of blind elephantnose fish, which live beneath the mats. They hunt by electricity and have well developed brains and learning abilities.
  • Birds and animals often make the floating island their home.
  • Pistia can purify stagnant water.

 

Note: outdoor photos are mostly taken in Ecuador and indoor photos mostly from Wisley Gardens.

 

Odd plants: Ruscus aculeatus

Ruscus aculeatus

Ruscus aculeatus

Ruscus aculeatus, or Butcher’s Broom, is a woodland shrub native to Europe, it has holly-like leaves and bright red berries. However there is a little more to this plant than meets the eye.

Ruscus aculeatus

Ancient Woodland Indicator

Ruscus aculeatus is an ancient woodland indicator plant, this means that its presence suggests a wood is more likely to have been around since before 1600.

How old is ancient? The chosen cut-off date, AD1600, around the time of the death of Queen Elizabeth I, is not entirely arbitrary. It marks the beginning of reasonably accurate estate maps, and also the first known widespread tree-plantings. Any wood known to exist in its present form by that date is almost certainly natural in composition even if it was heavily managed. (passage taken from britishwildlife.com, link below)

It is generally true that the older a habitat the more species it will contain and therefore the greater importance it has in nature conservation. However, it is not always easy to know exactly how old woods are; assessing species diversity is complex and documentation about an area is rarely complete, so alternative methods have been found using plants. Some vascular plants are known to not grow well in secondary woodland, and are often found in woods known to be ancient, so conclusions have been drawn that the presence of these plants suggest an older wood. This is not a foolproof indicator and the plants that show such growth habits are different in different parts of the country and on different soils, however, to botanists who have learned to study the signs, Ancient Woodland Indicators are an important clue to the history of the area.

More detail here

Leaves and Cladodes

Ruscus aculeatus

Ruscus aculeatus

Ruscus aculeatus is, at first glance, a fairly straightforward plant, it has pointed flat leaves, like a small leaved holly, a typical dicotyledon (more information about dicotyledons). However, looking more closely at the leaves, they are a little odd, firstly they are not horizontal to maximise the sun’s rays, they are end on. Secondly, the leaves have no evidence of veins, there is a slight crease down the middle, but not much else about them is leaf-like. Even more curious is that Ruscus is not is dicotyledon at all, but in the asparagus family, a monocotyledon, and so their leaves should be long and strap-like, with parallel veins. The reason these leaves do not conform to expectation of moncot leaves is because they are not leaves at all, but modified stems, stems that are specialised for photosynthesis, known as cladodes. Cladodes also appear in the cactus family.

A further clue that these are stems, not leaves, can be found in the flowers and fruits, which grow right in the middle of the cladodes, something which doesn’t tend to happen with real leaves.

Flower and unripe fruit

Flower and unripe fruit

Ripened fruit

Ripened fruit

There are also other Ruscus species with cladodes, again recognisable by the odd positioning of flowers and fruits. Below is Ruscus hypoglossum, the small protrusion above the fruit is the real leaf.

Ruscus hypoglossum

Ruscus hypoglossum

Family: Ruscaceae and Nolinoideae

Sansevieria

Sansevieria

The asparagus family (Asparagaceae) is one that has changed recently. Previously Ruscus was in the smaller family Ruscaceae, this has now been renamed Nolinoideae and is a sub family within Asparagaceae. Within Nolinoideae are some familar plants – Liriope, Ophiopogon and Polygonatum (Solomon’s Seal), plus a couple of exotic plants – Dracaena and Sanseveria – but it is the less familiar Danae racemosa and Semele androgyna (pictures below) that have cladodes and the resulting flowers and fruit sprouting from these.

Semele androgyna

Semele androgyna Leaf

 

Danae racemosa leaf and flower

Danae racemosa leaf and flower

Danae racemosa flower close up

Danae racemosa flower close up

 

Fasciation

Normal Flower and Fasciated Flower

Normal Flower and Fasciated Flower

Fasciation in plants is a bizarre mutation in the meristem (growing point) leading to flattened flower stems and distorted flowers, fruits and roots. It can also lead to a ring of small flowers surrounding the main flower, this is known as ‘hen and chicks’ and can be seen in some of the Veronicastrum pictures below. The meristem is where cells actively divide in order to grow or create new flowers and leaves, a disturbance to this process can lead to the cell division intensifying and occurring in a haphazard manner, leading to distortion. Essentially the growing point ceases to be a point and instead forms a cockscomb. For many plants this is most commonly noticed with flowers, which then go on to form distorted fruits, but with cacti and ferns it is often seen in the leaves.

Causes

Genetic

In some plants, such as the soybean (Glycine max), fasciation is caused by a single recessive gene. This means that fasciation will only occur if both parents of a plant have that gene and pass it on.

Multiple distorted flowers Veronicastrum 'Fascination'

Multiple distorted flowers Veronicastrum ‘Fascination’

Physiological

Normal and Fasciated Spathyphyllum

Normal and Fasciated Spathyphyllum

In plants without the gene, fasciation is caused by disturbance to the meristem at the time of growth. This disturbance can be caused by

  • Mites or insects feeding on the shoot
  • Fungal, bacterial and viral diseases
  • A sudden change in temperature – eg going from low to high or high to low (especially in Hyacinthus)
  • Zinc deficiency or nitrogen excess
  • Drought followed by heavy watering

Frequently Fasciated Plants

The following plants have exhibited fasciation: soybean, many cacti, ferns, Euphorbia, Prunus, Salix, cannabis, Aloe, Acer, Forsythia, Delphinium, Digitalis, Taraxicum and Syringa.

Artificially Induced Fasciation

In some cases fasciation is seen as a desirable characteristic, it can lead to increased yield in crops due to the enlarged heads, or provide a talking point in ornamental displays. Examples are the maize, Celosia cristata and Asplenium cristata (note the species name ‘cristata’ – cristate is another word for fasciation). To this end, the above conditions can be induced or one of the following methods used:

  • Manipulating the photoperiod (exposure to light)
  • Using susceptible cultivars (see below)
  • Using radiation – gamma rays or ionizing x-rays.
  • Chemical application – growth regulators or polyploidzing agents
  • A cutting or scion taken from a fasciated plant will create a new fasciated plant

Veronicastrum ‘Fascination’ is a cultivar grown for its tendency to fasciate.

Fasciated stem of Veronicastrum 'Fascination'

Fasciated stem of Veronicastrum ‘Fascination’

Veroncastrum 'Fascination'

Veroncastrum ‘Fascination’

Fasciation in Cacti and Other Succulents

Many cacti and succulents are subject to fasciation, although the word more commonly used to describe this state is cristate. More than fifty cacti genera have shown cristation, as well as the succulent families Crassulaceae, Asclepiadaceae and Euphorbiaceae. Some cacti have ‘Cristata’ in the name. Fasciated cacti form ribbon like weaves, or have many divisions. Cristation is often cultivated in cacti, with cuttings used to perpetuate the cristate cacti. It is thought that some cacti species have a genetic propensity to cristation and somatic mutation (genetic alteration caused by environmental factors as described above) leads to the physical changes. Seeds from fasciated stems in cacti often lead to fasciated seedlings, although this is not necessarily true of other plants, Digitalis, when fasciated, does not produce fasciated seedlings.

Mammillaria elongata cristate

Mammillaria elongata cristate

Some more cacti showing signs of cristation

Fasciated Mammillaria compressa

Fasciated Mammillaria compressa

Normal and fasciated Mammilaria

Normal and fasciated Mammilaria

Euphorbia

Euphorbia

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 Fasciation in Ferns

Several ferns are especially cultivated to be cristate, such as Dryopteris affinis ‘Cristata’ or Asplenium cristata

Asplenium cristata

Asplenium cristata

 Additional information and pictures:

Plant Divisions: Flowering Plants

Leaf Variety in Magnoliophyta

Leaf Variety in Magnoliophyta

Plants in the Magnoliophyta Division may also be called Angiosperms or flowering plants, they include grasses, palms, oak trees, orchids and daisies. Magnoliophyta is the only division that contains plants with true flowers and fruits, and all plants in this division use those flowers and fruits to reproduce. It is not known exactly when flowers first appeared, but definitely by 125mya and probably as far back as 160mya.

Flowers have proved to be an extremely successful adaptation, and despite its recent appearance, Magnoliophyta is by far the largest and most diverse plant division with over 250,000 different species and 500 families. (For comparisons to other divisions and their sizes see here)

Leaf Variety in Magnoliophyta

Leaf Variety in Magnoliophyta

Flowers

In Magnoliophyta, flowers replaced the cones of more primitive plants, as a means of reproduction. Some flowers are brightly coloured, have a scent or produce nectar in order to entice animals to pollinate them, but others use wind or water and, having no need to draw attention, are barely noticeable.

Flower Variety in Magnoliophyta

Flower Variety in Magnoliophyta

Flower Variety in Magnoliophyta

Flower Variety in Magnoliophyta

Fruit and what that really means…

All plants in this Division produce fruits of some kind, even though what they produce may not be easily recognised as fruit. The botanical definition of a fruit is a matured ovary (the ovary is the female part of the flower that contains the ovules which become the seeds once fertilised), this includes peppers, tomatoes, aubergines, nuts, peas, wheat grains, but not apples or rhubarb. There is another meaning for the word fruit, which is culinary and refers to a sweet part of a plant that is eaten, this is the more familiar term and includes rhubarb and apples, but not tomatoes and nuts, etc. ‘Vegetable’ is only a culinary term, referring to parts of a plant used in savoury cooking, it may refer to any part of the plant: leaves (lettuce) flower buds (broccoli), stems (celery) or roots (carrots) and has no botanical equivalent.

Classification

Being such a large and interesting division means that the classification of Magnoliophyta has received more attention and undergone more changes than any other division.

How Many Flowering Plants Are There?

It was believed for some time that there were over 400,000 flowering plants, but it turns out that many species of plant (not known as yet how many) have actually been named twice or even three or four times. The binominal naming system (using two Latin names, eg Helianthus annuus) was designed to make plant naming international and straightforward, but with people all over the world discovering and naming plants and no comprehensive way of cross referencing them, we have ended up with a lot of confusion. Now, partly due to the international power of the internet, serious attempts are being made to work out how many actual species there are and to remove duplications. The Plant List is a collaboration between a number of botanical gardens around the world and has an impressive online collection of these names.

DNA Alters The Family Tree – Cronquist to APG III

Before DNA testing was possible (or DNA was known about) plants were collected into families, classes and orders according to detailed studies of how they looked.

Over the past few hundred years there have been many different classification systems, but one of the most commonly used and straightforward was the Cronquist System, devised in 1968. This System grouped plants into families, with the families grouped into orders, orders then grouped into sub classes and sub classes grouped into two classes: monocotyledons and dicotyledons. However, with genetic testing, it has been found that many of these groupings were wrong. A new system, called APG (Angiosperm Phylogeny Group), was introduced in 1998, but has subsequently been updated twice since then and will no doubt change in the future.

Frustratingly, what was once a very neat and straightforward system of classification has become an unwieldy, confused and messy system, because nature is never neat. The new system, called APG III, does not use classes and subclasses, instead it groups orders within clades, nested within other clades, nested within other clades; with some families not fitting into any clade at all.

The following diagrams are an attempt to show the changes in a simple manner, using images of plants to represent different orders and showing how those orders have altered their connection to others. It is clear that some assumptions were completely wrong, for example some dicots are more closely related to monocots than other dicots; the buttercup is not kindred with the water lily; cacti are more connected to Heuchera than originally thought and oak trees are closer to Euphorbia than London planes.

Cronquist system

Cronquist system

APG III System

APG III System

Key to Magnoliophyta plants

Key to Magnoliophyta plants

Note: I was unable to take photos of a tulip tree or Rhododendron in flower, so used photos I got online from here: Rhododendron and tulip tree

 

It was also fairly tricky to find all the necessary information about where plants appear in the Cronquist system, if anyone spots any faults, please contact me at the email to the right. Most of my information came from Wikipedia, and from here

To enlarge the key click the thumbnail

Anthurium and Ctenanthe - two flowering plants

Anthurium and Ctenanthe – two flowering plants

Plant Divisions: Gnetophyta

Ephedra cutleri

Ephedra cutleri

Gnetophyta is a plant division containing only 3 genera and approximately 80 species. It isn’t known when plants in this division first evolved, but somewhere between 140 and 250mya. Although gnetophytes are gymnosperms, with no true flowers or fruits, they have some features in common with flowering plants:

  • Vessel elements in the vascular system not seen in other gymnosperms
  • Both Welwitschia and some Gnetum species are pollinated by insects
  • Flower like structures on male cones of Welwitschia
  • Nectar – produced on the tip of the cones rather than in a flower

All gnetophytes are evergreen and woody, and may be trees, vines or in the case of Welwitschia, difficult to classify. These plants have not been studied much and it is tricky trying to find out information about them. For example, although they are mostly considered dioecius (male and female cones on separate plants) all three genera sometimes produce bisexual cones, containing both stamen and ovules, but it isn’t really understood why, or if these cones can then reproduce.

Gnetophyta Family Tree

Gnetophyta Family Tree

Gnetophyta Family Tree

Gnetum

Gnetum gnemon

Gnetum gnemon

There are 30-35 species of Gnetum, including two trees, many vines, and shrubs.

One tree, Gnetum gnemon, reaches 15-20m tall, and does not have fruits, but a fruit-like juicy covering for the seeds, which, like fruit, are edible to birds and aid in the spreading of seed.

Many Gnetum have seeds and leaves that are also edible to humans. Leaves of Gnetum have network of veins, something seen in dicotyledonous flowering plants, but no earlier evolved plants. All are dioecious. Gnetum are thought to be the first plants to be insect pollinated, by now extinct scorpion flies.

Welwitschia

Welwitschia

Welwitschia

Drops of nectar on female cones - Barry Rice/CalPhotos/EOL

Drops of nectar on female cones – Barry Rice/CalPhotos/EOL*

There is only one species of Welwitschia and it only grows in the deserts of Namibia and Angola. Despite sometimes growing 10m wide (although more commonly 4m wide), Welwitschia has just two strap like leaves that grow continuously. The longest recorded leaves were 37m long, but most leaves break up in the harsh desert environment and become tatty and brown at the ends. Unlike Gnetum, the veins are parallel, as seen in monocotyledonous flowering plants as well as some ferns and cycads.  Welwitschia probably live 1000-2000 years, although this is difficult to know for sure. The female cones produce drops of nectar to entice insects to pollinate them. They have a single tap root grows deep into the sandy desert soil in search of water.

* Photo from The Encyclopedia of Earth with some more technical details about Welwitschia

19th July 2013

19th July 2013

31st August 2013

31st August 2013

I recently bought some Welwitschia seeds to see how they would grow. I planted them in a pipe to give space for the deep tap roots, 2:1 sand to compost. Within a week, three had germinated. Two died a few weeks later, I believe because I didn’t take into account that the single root only takes water from deep in the soil, so watering from above was pointless. I spray with fungicide every week or so. As can be seen from the pictures, Welwitschia has two cotyledons that start out orange and turn green.

Ephedra

Ephedra chilensis

Ephedra chilensis

There are about 50 species of Ephedra. They have slender stems with needle like leaves and small, sometimes brightly coloured, cones. They grow in dry areas in the Northern hemisphere, such as North Africa, Europe and North America. Ephedra looks very much like a gigantic version of psilotum (see previous blog about ferns) and can grow up to 3m. Some are monoecious.

The Evolution of Attracting Insects

While researching the previous blog about Ginkgophyta I learnt about terpenoids. Terpenoids are chemicals produced by both primitive plants (eg mosses and ferns) and flowering plants, the last group of plants to evolve. However, the function of terpenoids has altered as the plants have evolved. Terpenoids attract certain beneficial insects that feed on other insects that are harmful to the plant and this is an advantage to all plants, however, in later plants, Cycadophyta, Gnetophyta and Magnoliophyta, the insects attracted are also used to pollinate the plants and it was presumably because of the existence of terpenoids that such a partnership of plants and insects was able to form. Insect pollination is a far more efficient means of transporting pollen than wind, because an insect seeks out another plant, often a specific insect becomes an exclusive visitor to a specific plant. In the case of Welwitschia, growing in the desert, there may be many kilometres between plants, an awful lot of pollen would need to be produced in the hope of it being carried on the wind. Using insects to transport the pollen is akin to getting the postman to post a letter through the letterbox of the person you want to reach, instead of throwing  a thousand leaflets down the road they live in, in the hope they pick one up.