Tag Archives: Plants

Plane Tree Dust – The Scourge of the Chelsea Cough

So here’s an issue no official sources seem to be talking about: Plane Tree dust.

I work as a gardener in Central London and for me, and all gardeners who work beneath plane trees, the orange dust from Platanus hispanica causes huge issues. It leads to not just sneezing and itchy eyes, but uncontrollable coughing fits. I see colleagues of mine brought to their knees by coughing. I see their red eyes and hear constant sneezing. I’ve even heard cyclists complaining about it to each other as they whizz past.

Most worrying is that I think it may be getting worse, but there seems to be very little official recognition that there is a problem. A scout around the internet for information turned up almost nothing. The occupational therapist at my work had never heard of it. So I wanted to find out what is actually happening? Is this really only a problem for gardeners? Is climate change increasing the problem? And how worried should we be about it?

In this blog is everything I’ve discovered and I’ll be contacting anyone who might be able to tell me more, but if any of you out there have personal experiences or professional knowledge about plane tree dust, then please comment on here, or write to me – my email is at the bottom of the page.

Plane trees are beautiful, with their flaky bark, palmate leaves and dangly seed pods. They were planted in great number in London in the 18th century and are considered of great importance because they provide a huge canopy, are generally tough and resistant to pollution. There are roughly 379,000 in London. That makes up 7.2% of the capital’s tree population, but due to their huge canopies, they make up the biggest leaf area of any London tree species.

However to anyone working outside in London, they are known as serious trouble. Every gardener I have spoken to has described them as being their biggest hindrance to doing their job. Plus I know of a tree surgeon who refuses to work with them after being put in hospital with asthmatic fits. Around Chelsea Flower Show time, people talk about the Chelsea Cough. In Australia there have been protests and demands that the trees are banned.

There is some dispute over what causes this problem. When I started looking into this, I found plenty of research into Platanus pollen, but pollen isn’t the problem, it is the orange dust that floats down like snow and gets into the grass and coats the soil. The dust is largely made up of a fluffy coating in the seed pods (it helps the seeds float, like dandelion (Taraxicum officinale) seeds) but it also contain trichomes, tiny hairs that coat the leaves. These trichomes are thought to be the main cause of coughing. As James Wong explains here, antihistamines won’t work against trichomes, they are an irritant, which is more serious than an allergy.

The Reasearch

I found three studies into the effect of plane trees on the public. They include research from Australia, France, Spain and Italy. The effect of plane trees is acknowledged as often extreme, however all these studies focus on the effects of pollen. Some mention that it is odd that the reaction to plane trees happen outside of the pollen season, all find that plane tree pollen only affects a few people.

Australia 2011 study

Spanish1997 study

Spanish 2010 study

There are also scientific studies into trichome regulation, but these don’t seem linked to allergies.

Conclusion

Well, that’s all I have and it’s not much at all.

What worries me is that I think with the change in climate, this problem is getting worse. Because there are no studies I’m only going by what long-standing colleagues say, but the effects are so extreme and the awareness so small it makes me think it can’t have been as bad in the past.

Is global warming having an effect on the production of trichomes and the seed bristles?

And if so, do trichomes have an effect that lasts beyond the coughing fits – since prolonged exposure to dust can lead to long term health issues, should we be worried?

I shall continue to investigate and update later, but if you have information or personal experience, then either comment below or contact me via email on

therealtetrapod @ gmail .com

Latitudinal Diversity: my theory

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.

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.

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.

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 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

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

Insect galls in Ecuador

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.

Mosses and lichen on a branch

Schachen Alpine Garden

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.

Anthyllis vulneraria

Gentiana angustifolia

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)

Water droplets balanced above leaves

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)

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.

Pine growing from the rock

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.

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.

Lichen growing on pine tree

Wild orchids grew on the mountain also.

My favourite two photos from the trip:

Thistle flower

Red spotted bug

Schachen Alpine Garden

Plant Families: Araceae (aka Aroids or Arums)

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).

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 Leaves

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

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

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

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:

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.
Being submerged provides a little protection, even if eaten or stepped on, the Stylochaeton still has half a flower remaining.
The fruits are eaten by something small. Having eaten the fruit, the seeds can be dispersed in the faeces.

Stylochaeton lancifolia

Tropical

2346

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.

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.

Some Amorphophallus inflorescences

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.

Lichen mimicking stem

Epiphytic Examples

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

Temperate Woodland

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.

Fasciation

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’

Physiological

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’

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

Some more cacti showing signs of cristation

Fasciated Mammillaria compressa

Normal and fasciated Mammilaria

Euphorbia

Fasciation in Ferns

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

Asplenium cristata

Additional information and pictures:

Plant Galls in a Cloud Forest in Ecuador

On a recent trip to an Ecuadorian cloud forest I was fascinated by the large numbers of diseases and deformities that riddle the plants. Many of these take the form of plants galls.

Galls are abnormal tissue growth on the surface of plants caused by parasites, such as fungi, nematodes, insects, mites or bacteria, the galls are tailored as the perfect place for the parasitic organism to live in. In the past I’ve looked for and found plant galls in England, but it seemed that they were more numerous and varied in Ecuador. I believe there are three reasons for this, all related to Latitudinal Diversity, which is the phenomenon whereby animal and plant species diversity increases the closer you get to the equator, it applies most notably to rainforests.

With a wider variety of plant hosts, there will be a wider variety of parasites to take advantage of them
A greater number and wider variety of insects leads to more varied insect galls
It is not known for sure that there are more species of fungi and bacteria close to the equator, but it is likely since fungi and bacteria both benefit from a stable environment where light, temperature and humidity are fairly constant, all of which is more true at the tropics than further North or South

What makes galls particularly bizarre, is that these growths are not attachments to the plant, but the plant itself, made to alter its normal growing behaviour in order to benefit its parasite host. Although it is not clear how insects cause this change, bacteria is known to insert its own DNA into the plant cells to alter behaviour. (example here) Insect larvae have been found actually inside the cells of the plant, which might suggest similar interference. It is thought that one wasp (Cynipinae) works in conjunction with a virus (viruses reproduce by inserting their own DNA into the DNA of a host) that lives in the wasps saliva and gets into the plant as the wasp eats it. This is an example of mutualism, since the insect benefits from the virus by getting to make the gall and the virus benefits by getting to reproduce.

Insect and mite galls

These galls are formed by the insect or mite either feeding or laying eggs. When adults lay their larvae on a leaf, excreta or saliva from the insect affects the cambium and causes it to grow differently (more detail above). The larva then grows inside the gall, feeding on the gall itself, eventually eating its way out and escaping. Sometimes the insect control over the plant tissue extends beyond the gall and starches and sugars are drawn in from elsewhere in the plant to increase the food store for the insect.

Insect and mite galls in Ecuador

Insect gall on tree trunk

Underside and Upperside of Leaf

Insect galls

Insect galls on Columnea

Insect galls showing holes of escaped insects

Non Gall Insect Invasions

Sometimes I found insects that had taken over leaves, or even entire plants to make a home in. These were not galls, because while leaves were often distorted, the cells were not expanded or changed, but they were still quite bizarre to see.

Ants Forming a Home in a Plant

Wasp Swarm onto Leaf

Insect Colonise a Leaf

Note: for other insect photos I took in Ecuador, see here

Other Galls

Although some galls I was clearly able to determine as being caused by insects or mites because I could find the animal or see its exit point, others I am just not sure about. The following are those less easy to decipher galls that may be caused by fungi or bacteria.

Leaf Spot Gall

Leaf Spot Gall on Decayed Leaf

Leaf Distortion

The plant in the next photo is a puzzle, the fluffy looking outgrowths at the base of the leaves (and in between) may be a normal part of the plant, perhaps even be the flowers, but they also look similar to the growths in the above picture, which are definitely galls.

Plant Galls or Plant?

This final gall, I believe, is caused by insects because I think it is possible to see them, the black mass at the heart of the distortion.

Severe Leaf Distortion

Close up of Leaf Distortion

Some interesting and useful websites on plant galls:

Some books I used for reference:

British Plant Galls – M. Redfern and P. Shirley
The Kingdom Fungi – S. L. Stephenson
Parasite Rex – C. Zimmer

Cloud Forest in Ecuador

Busy forest life

Note: this blog is an introduction and will deal with the forest as a whole, the general impression of it, I hope to write future blogs about specific aspects, such as orchids, fungi, diseases etc, and here is a separate blog page I posted about insects and animals.

I took a recent trip to a cloud forest in the mountains of Ecuador, working at a research centre called Los Cedros. While there I was able to take many hikes out into the forest, taking photos and trying to understand how the forest worked as a system.

Cloud inside the forest

A cloud forest is a type of rainforest, but at a higher altitude and therefore cooler and with a frequent covering of cloud. During the day, the cloud could be seen moving through the forest, like mist, and up and down the mountain.

Cloud moving down the mountain

The plants in a cloud forest and a rain forest are similar, with the same high species diversity, the same density of plants and the same complex interaction between plants, animals and fungi.

Trees

Aerial roots hang down from a tree (3 vertical white lines)

The majority of the trees were very tall, very thin, with no branching until reaching the top of the canopy, this is typical of the rainforest. The forest was always dark because the canopy was so dense and so leaves were concentrated as high up as possible where they could reach the light (what looks like white sky behind the trees is actually misty cloud between them). Lianas and aerial roots hung down between the trees.

Tree ferns with a backdrop of mist

Among the trees were tree ferns, palms, strangler figs and walking trees.

Epiphytes and Climbers

Epiphytes

Aroid in tree top

Wall of climbers next to a path

Trees were covered in plants, some were climbers, such as Philodendron, others were epiphytes that grew around the trunks of trees, using moss as an anchor, these were mostly orchids, bromeliads and ferns. Epiphytes grow high in order to use the increased light in the canopy layer, they have a number of methods to gain nutrients and water, normally provided by the soil. For example, bromeliads have stiff leaves that form a cup at the centre, water collects in this cup and insects defecate and drown in it, leading to a release of nutrients.

Bromeliads

Orchid in tree

Mosses and Lichens

Moss, lichens and epiphytic ferns covering tree branches

Mosses were abundant, covering leaves and trunks, they were virulent and colourful. Some more detail on mosses is here.

Moss and lichen

Moss growing on leaf and stem

Ground Cover

Leafy ground cover

Mostly the forest floor was covered in leaves, thick plasticky leaves, a little like cherry laurel. The soil in rainforest is thin and low in nutrients, this is because there are so many organisms with cunning ways of exploiting death, snatching plant and animals corpses before they reach the soil. There is also very little light on the forest floor, perhaps as low as 2%, however, there were some plants that managed to grow and thrive.

Kohleria villosa

Blechnum fern

Stellaria media (chickweed) and Plantago major (greater plantain) are both familiar weeds in England that have been introduced to the area, presumably by accident, and I found them growing wherever the forest had been cut back.

Plantago major (greater plantain)

Diseases

Partially decayed, but still attached leaf

Warm, humid conditions are ideal for many diseases, add to that the large number of insects and parasitic plants and fungi, meant that most plants were damaged extensively. Non native trees, such as citrus, were the most affected, so presumably the native plants have built up some resistance, but the forest was still filled with diseases and decay.

Fresh new growth on a diseased fruit tree

Diseased orchid leaf

Dilapidated leaves

Plant Divisions: Flowering Plants

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

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

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

APG III System

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

Plant Divisions: Gnetophyta

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

Gnetum

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

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

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

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.

The Reasearch

Conclusion

The Facts

The Theories

My Theory – it’s all about the small things

First, some terminology

Parasitism

Symbiosis

The Small Things

Fungi

Bacteria

Insects

Conclusion

To put it simply…

A Few Basic Facts

Adaptations

Reproduction

The Generic Process for Monoecious Aroids

Two Specific Examples of Monoecious Reproduction

Reproduction in Other Aroids

Habitat

Arid

Some Examples

Tropical

Terrestrial Examples

Epiphytic Examples

Temperate Woodland

Aquatic

An Example

Dracula Orchids

Tiny Orchids

Causes

Genetic

Physiological

Frequently Fasciated Plants

Artificially Induced Fasciation

Fasciation in Cacti and Other Succulents

Fasciation in Ferns

Additional information and pictures:

Insect and mite galls

Insect and mite galls in Ecuador

Non Gall Insect Invasions

Other Galls

Note: this blog is an introduction and will deal with the forest as a whole, the general impression of it, I hope to write future blogs about specific aspects, such as orchids, fungi, diseases etc, and here is a separate blog page I posted about insects and animals.

Trees

Epiphytes and Climbers

Mosses and Lichens

Ground Cover

Diseases

Flowers

Fruit and what that really means…

Classification

How Many Flowering Plants Are There?

DNA Alters The Family Tree – Cronquist to APG III

Gnetophyta Family Tree

Gnetum

Welwitschia

Ephedra

The Evolution of Attracting Insects