Greening the Red Planet

By Sophie Harrington

It’s a big universe out there, and it takes a long time to get anywhere. Even just heading to Mars would take us over 6 months. A bit further than popping down to the pub then! But if NASA and a whole host of other private groups get their way, it won’t be too long before we’re sending humans out to Mars.

Mizuna growing on the ISS (credit NASA)

Mizuna growing on the ISS (credit NASA)

The logistics of the operation are still being worked out. Some argue it’s better to send astronauts on a one-way mission, setting up a bare-bones colony that will grow over time as more and more colonists make the voyage to the Red Planet. It would be handy not to carry all the fuel needed to launch a rocket off of Mars, but sending humans on a one-way trip might be a bit too much for NASA. Private groups, like Mars One, might seem more likely to support such a remarkable attempt, but it’s unclear where their funding will come from.

Whether or not we send humans to stay on Mars to begin with, it can’t be denied that colonising another planet would certainly capture the imagination. But what would that really entail? It’s well and good to talk about sending humans to Mars, but how on earth are we going to survive?

Enter plants, which will probably be our most prized possession on Mars, and in outer space for that matter. Even Apollo astronauts grew tired of their space-certified food, and they were only in space for a matter of days. While the food has definitely improved, the sheer delight of ISS crewmembers when they were able to have a few mouthfuls of fresh Mizuna, grown on the spacecraft, suggests it still leaves much to be desired.

Artist's conception of a greenhouse on Mars (credit NASA)

Artist’s conception of a greenhouse on Mars (credit NASA)

NASA recognises that to send astronauts on long-term missions, some form of fresh food will likely be necessary. Besides the culinary and psychological benefits of fresh veg, hardly any of the food packages currently in use on the ISS would survive the length of a trip to Mars. Sending astronauts up with lettuce, tomatoes, rocket, and even courgette could provide badly needed nutrition while livening up the interior of the spacecraft. Who said interior design wasn’t important in space?

Once on Mars, one of the first structures built by the colonists would have to be a greenhouse, where vegetables can continue to be cultivated. In the long term, we would be able to grow more intensive crops such as maize and wheat, which while requiring refining to be edible would help bulk up a diet, and reduce the dependence of the colonists on food supplies from the home planet.

Some researchers have even found that plants can grow perfectly well on Mars-simulant soil, in some cases even better than on Earth soil! Perhaps colonists may start gardening outside, beginning a process of terraforming that could change the face of Mars itself.

It might not be called the Red Planet for long!

Plant factories: making organic pesticides?

By Tom Evans

In many peoples opinion, pesticides were one of the great tragedies of 20th century agriculture. They symbolized man’s dominance over nature: of the synthetic taming the organic – a cruelly ironic leitmotif of the modern world. In our post-Green Revolution era, most agricultural scientists see pesticides as anathema. Not only do they destroy the land and its biodiversity, but they also apply selection pressure onto insects to evolve resistant strains. The focal challenge of contemporary agriculture, then, is to devise new ways we can tame nature without inadvertently breeding resistance, or further damaging our precious ecosystems.

The bombyx mori silk moth

The bombyx mori silk moth

A recent paper in Nature Communications is part of a global effort to do just that. And, unsurprisingly, the answer comes through working with – not against – nature. A team of researchers from Kansas State University has genetically engineered a species of tobacco to produce chemicals known as pheromones. Plants do not usually make pheromones; in fact, they’re chemicals that insects produce, and they are usually involved in the communication systems of insects. For example, female silkmoths attract mates by producing a pheromone called bombykol. Male silkmoths can smell thispheromone from up to 10km away and follow the scent trail until they locate the female producing it.

So why has this group of scientists created a plant that makes pheromones?

The idea is we can harvest pheromones from plants and then use these natural chemicals in fields to control insects. At the moment industrially producing pesticides is bad for the environment, as well as the health of those working in pesticide factories. It’s also quite costly. By genetically engineering plants to synthesize pheromones, a so-called “plant factory” for pheromones could theoretically be established in the future, providing an environmentally friendly and cheap form of pest control. And moreover, the message is clear: nature is not our enemy, but our closest ally.

Mathematical Patterns in Plants: Fibonacci and The Golden Ratio

By Ellie Archer

Spiral patterns abound in nature, manifesting themselves in plant petals, sunflower heads and pine cones. Remarkably, the maths behind these patterns all stems from one simple number: the golden ratio.

What is the golden ratio? Mathematically, it is the number ϕ such that ϕ = 1 + ϕ-1, approximately equal to 1.61803. Visually, if we draw a rectangle with sides in the ratio 1:ϕ, we obtain what is deemed to be the “perfect” rectangle (indeed Da Vinci used these rectangles to paint the perfect proportions for the Mona Lisa’s face). We can then construct a sequence of golden rectangles, as in the picture, inside of which we may inscribe the Fibonacci spiral, and it is precisely this spiral that we see exhibited so frequently in the natural world.

 

fibonacci

The Fibonacci Spiral (Image credit: people.rit.edu)

Perhaps the most classic example in nature is that of seed arrangement in a sunflower head. The seeds spiral out from the centre, and the problem is how to arrange the seeds to make the most efficient use of the space available. If you spiral too tightly, the seeds get squashed too close together and do not have sufficient space to mature. If you spiral too slowly, a lot of the space available isn’t utilised. It transpires that the most efficient path to take is a Fibonacci spiral.

Why is this? Imagine we are tracing a spiral by forming a seed, then rotating through a certain angle, then forming a new seed, and repeating. Suppose we make a quarter turn between forming each seed. We just end up with four straight lines of seeds, branching out from the centre in a cross shape. A similar thing occurs if we take any simple fraction (such as 5/7 or 1/31, giving seven or 31 branches respectively). Perhaps if we take an irrational number, say π, things may be better. But in actual fact π is very close to 22/7, so again we get seven branches, this time with very slight spiral behaviour.

ϕ is special because it is pretty much as far from a simple fraction as it could be.  Repeatedly applying the relation ϕ = 1 + ϕ-1, we can write it as the following infinite fraction:

This means that rotating through a fraction ϕ of a full turn avoids building up branches with empty space in between. Instead we get a pattern as shown in the sunflower, which is in fact a lot of Fibonacci spirals.

sunflower

Fibonacci spirals in sunflowers (Image credit: brilliantbotany.com)

The golden ratio is deeply connected to the Fibonacci sequence (0, 1, 1, 2, 3, 5, 8, 13, 21, …, where each term is formed by adding the previous two). Though the Fibonacci numbers were initially studied in relation to mating patterns in rabbits, it turns out that the ratio between two successive Fibonacci numbers is very close to ϕ, and indeed gets arbitrarily close as we take larger Fibonacci numbers. This means that the total number of spirals we see is usually a Fibonacci number, and if we count spirals going in opposite directions, we get two consecutive Fibonacci numbers, as shown in the pine cone below.

Pine

Fibonacci spirals in a pine cone. We count 13 and 8 spirals in each direction, both Fibonacci numbers. (Image credit: http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibnat.html)

There are countless examples of this in the plant world. Not only does this explain why three-leafed clovers are far more abundant than their four-leafed counterparts, but next time you see a daisy, take a look: chances are it’ll have 21 petals!

Anything you can do, plants can do better!

By Stephanie French

The other week I bumped into a friend of mine in Sainsbury’s. We were chatting away as usual when he asked me: “are plants alive?”. I thought to myself that this was just another example of how under-appreciated the Plantae kingdom is, and yes, of course, most people do know that plants are alive, but many perceive them to be boring, simple lower-life organisms.

Credit: Atanu Saha

Credit: Atanu Saha

However, this is far from the truth; land plants actually evolved after animals, and in some ways are more complex. For example, while animals can move away from poor environments, plants are forced to cope with whatever nature throws their way. They may not appear to change very much in different weather conditions, but within plants hundreds of dynamic signalling events are occurring from the cellular to the whole-plant level allowing the plant to survive in extreme environments. For example, during high light-stress, plants can move chlorophyll within their cells to more “shaded” areas, rapidly move their leaves, develop surface reflectants (pubescence), and dissipate excess heat using the xanthophylls cycle…the list goes on. Plants, unlike animals, are actually acclimating throughout their entire life cycle.

Further complexity of the plant cell can be seen just by looking down a microscope, or thinking back to the classic ‘animal cell vs plant cell’ picture present in nearly all high school biology text-books. Plants contain more organelles including, of course, chloroplasts! And, sure, animal cells can differentiate to form more complex-looking cells such as nerve cells, but plant cells can do that too (e.g. sieve-tube elements). Also, although not generally realised by most people, plants can form organs like animals too – leaves and flowers etc. are indeed organs. Do you know any animals that have chloroplasts? I think not (ok actually there are actually three but they steal the chloroplasts from plants)

And if you thought your love life was complex, for plants it is (probably) even more so. As angiosperms (flowering plants) can produce multiple stamens (male-parts) and carpels (female-parts) there is so much more potential for variation. A single flower can be male or female or hermaphrodite. On the whole plant, all flowers may be the same sex or there may be a combination of male, female or hermaphrodite flowers. Plants even have a complex mechanism called self-incompatibility, to prevent inbreeding.

When sex does occur, it is twice as good as in the animal kingdom. Double fertilization occurs whereby one sperm cell penetrates the egg cell while another penetrates a different cell called the central cell. Both these cells develop within the seed, the former forming the embryo and the later forming the endosperm, which provides nutrients to the developing plant.

In fact plants are so complex and diverse that they even confused Charles Darwin! He frequently referred to angiosperms as an ‘abominable mystery’, as he could not figure out what the most ancestral flowering plants looked like or why they diverged so rapidly. This is still disputed over by many scientists! One theory is that by using other organisms to carry their gametes, angiosperms were able exploit many niches and diverge in a short space of time.

These are just a few of the many reasons why plants deserve so much more respect than they currently receive. So much research is focussed on animals, with the possibility that it may enable future drug discoveries, which of course is great. However, plants have the potential to increase crop productivity and provide the world with renewable energy, so research on plants is equally, if not more, important.

The Little Fungus that Could

By Nathan Smith

Deep in the dark depths of fungal taxonomy there lies a phyla known as the Glomeromycota. Members of this phyla are all obligate symbiotes, unable to support themselves independently and requiring a photosynthetic partner to provide organic carbon to them in return for gifts of phosphorous and nitrogen. For all bar one, this photosynthetic partner is a terrestrial plant; the symbiosis being better known as Arbuscular Mycorrhization and which upwards of 80% of angiosperms (flowering plants) are capable of engaging in.

The exception to this Golden Rule of the Phyla? A species known as Geosiphon pyriformis which instead forms a relationship with the cyanobacteria, specifically the species Nostoc punctiforme.

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Geosiphon:Nostoc symbiosis; Geosiphon spores inset
(credit Schuessler Lab)

The Geosiphon:Nostoc symbiosis appears to be unique in nature as the only example of an endosymbiosis between a fungus and a bacteria.  Adding to its mystery, it has so far been reported to have been found only 6 times in the wild in a small region of eastern Germany and Austria.

In contrast to Arbuscular Mycorrhization, where the fungal partner invades the cells of the plant to create an exchange interface, the cyanobacteria are taken in by the fungi, surrounding them with a unicellular structure known as a ‘bladder’ that can grow up to 2mm in length.

The exchange of nutrients is also different than in Arbuscular Mycorrhization. With the exception of nitrogen and carbon, all of the cyanobacteria’s nutritional needs must be met by the fungus. In return, the fungus receives organic carbon and nitrogen.

It is possible that Geosiphon:Nostoc symbiosis represents an important step in fungi being able to form symbiotic relationships with plants; it’s also possible that the Geosiphon:Nostoc developed out of the wider spread Arbuscular Mycorrhiza symbioses.

Either way it’s an interesting story of one fungus breaking the mould.