Monday, 6 April 2020

Finally, Furahan plants! ('Plants VII', also 'Post #250', and 'Twelve years on')

Click to enlarge; copyright Gert van Dijk

Experience taught me that posts about plants do not attract many readers and do not generate many comments. If I wanted to maximise interest, I would probably do better to keep plants in the background and focus instead on big fierce animals with lots of teeth, or spikes, or thagomisers. But I write these posts because I like to learn (and teach, I guess).

So, this post will be about Furahan plants. For those diehards who wish to read up on the subject, see the list of posts at the end of this one. The reason to write it now is that I am working on a chapter on plants for The Book. Doing so forces me to think about the specifics of the object I am working on and to make some decisions. For instance, the wish to paint early explorers, who look at the planet Furaha from their spaceship, forced decisions about how artificial gravity and the aesthetics of interior spaceship design. Likewise, having to paint trees forced me to collapse the uncertainties about Furahan plant life into ‘facts’, although it is more like pruning fantasies: only one remains.

The very first sketches involving Farahan plants showed shapes something like the one above. (This is a quick inelegant sketch made for this post; I will show paintings of such tree designs that are now wholly defunct in a later post.) They usually had very thick trunks and had a few gigantic leaves. They were obviously alien and, I thought, visually quite appealing. But the decision to set the threshold for biomechanical aspects of Furahan life at its minimum level of ‘feasible’ dealt as much a death blow to these large leaves, as when it killed ballonts.

So Furahan plants have Earth-sized leaves, making them rather mundane. Why? Plants, as all organisms, have to find compromise between conflicting demands. If the only requirement would be to provide a place for photosynthesis, then a large thin surface would do, resulting in something resembling a bed sheet held up at a right angle to the rays of the sun. Well, that’s not what plants look like, and there must be a reason for that...

Two very important factors determining leaf size turn out to be temperature and humidity. Leaves catch light, and unfortunately that warns them up too. Even though leaves are very good at reflecting infrared light, and do not therefore warm up that easily, excess heat is still a big problem. One reason for that is that (on Earth!) photosynthesis becomes less effective at temperatures above 26 degrees. Leaf size is important for that because the air around a leaf forms a ‘boundary layer’ slowing heat exchange. This layer is bigger for large leaves, so large leaves run the risk of warming up too much. You would expect that plants in hot climes would be small, right? Maybe, but Victorian scientists had already noticed that the biggest leaves are found in the tropics, right where they shouldn’t be.

Click to enlarge; copyright as indicated; source

Leaves have tricks to cope with overheating: as the figure above shows, fake leaves in cooling experiments cooled more when they had lobed, leaflike, edges than when the edges were straight. Apparently, bits of leaf closer to an edge cool down better. Another way to stay cool is to have water evaporate from the leaves. Unfortunately, that requires lots of water, so this trick is best reserved for humid regions where water is readily available. Cooling isn’t always beneficial though: at night or in cold climes low temperatures can damage leaves, so then the ability to keep warm becomes important.

In short, leaves have overheating, freezing and water loss to contend with, all of which are affected by leaf shape and size. So how do you balance all those demands? In 2017 scientists put it all together by studying 7670 species of plants worldwide (Wright et al 2017), and finally managed to understand why big leaves are found in the tropics, right where you think they shouldn’t occur.
Click to enlarge; Wright et al 2017; source here

This figure and its legend say it all. Leaves can be big if there is lots of water to cool the leaves during daytime and also if it doesn’t get cold enough at night to harm the leaves. Basically, we are talking about tropical rain forests. That explains the circumstances under which leaves may get large, but not yet which benefit they derive from that. The authors say they think that large leaves need less twig mass, which is good because twigs do not contribute to photosynthesis. They also think that large leaves help when temperatures are marginal.

I expect that wind has an impact too, but I found surprisingly little information of the impact of wind on optimal leaf size. The reason for that lack might be that the really leaves I had in mind, from towel-sized ones, through bedsheet-sized leaves to small-sailboat-class giant leaves, do not occur on Earth. I guess that the typical tree branch anatomy, with each leaf attached by a stem to a twig that is attached to a bigger twig, etc., is a trick to absorb forces. If forces are absorbed at each level, the next level only has to carry part of a bigger load it would otherwise carry in its entirety.

Click to enlarge; Copyright Vogel et al 2009; source
Regardless of that, leaves have nice mechanical tricks to reduce the force of the wind. Some leaves take on conical shapes in a strong wind, and in other species all leaves on a twig together bundle up and reduce wind drag. The shape of the leaf even helps bring such curling about.

So where does that leave (pun intended...) those truly alien plants with giant leaves like sails? Well, nowhere. Their remaining niche would be somewhere where leaves suffer no ill effects from heating up or cooling down, or where the wind cannot harm them. The planet Furaha has wind, and its leaves do not like heating up very much. In that way they are Earth-like. So they have leaves in a form of flat thin sheets of tissue on stalks, connected to twigs, etc. It’s all rather Earth-like and boring.

But do not worry; the fact (’fact’...) that Furahan photosynthesis is more efficient than Earth’s ridiculously inefficient system ensures differences in how they look, and so does the ‘fact’ that Furahan photosynthesis responds to different portions of their star’s spectrum than Earth photosynthesis. Of course, there are the architectural differences in overall shap and trunk design too. But more on that later.

Earlier posts on alien plants
Alien Plants I
Alien Plants II
Alien Plants III
Alien Plants IV
Alien Plants V
Alien Plants VI

"Twelve years on"; Yes, I wrote the first post in this blog in 2008. This is also the 250th post I have written on Furahan Biology and Allied Matters. I intend to pick up the pace a bit from the extremely sedate rate of new posts you have enjoyed the last few years, so no big celebrations right now. Perhaps just a small applause for keeping the blog -largely- alive for twelve years?              

The main site has now moved to a new host, and some things broke while moving. They always do. I will repair them in the coming weeks. 


Keavan said...

Giving plants a different starting point and different materials to play with should really be enough to get some unearthly designs.

Wow, by my best guess I've been lurkily following this blog since 2011. Time flies.

Anonymous said...

what if a planet had no "plants" and its main producers are a separate group of photosynthesizing "plant-animals"? would such an ecosystem make sense if there are few or no sessile producers and instead they took on the forms of "air plankton" or "swarming plant-insects" or even tall, slow-moving migrating "trees"?

i guess one complication of such an ecosystem is that in a world where plant-analogues can run away or fight back, the "herbivores" would effectively have to be predators in a way to catch their food...

Kevin the horse said...

It's nice to think of alien plants too and how they'd evolve, everyone focuses more on the animals but one must remember plants are just as active players in the evolution game and not just "scenery".

That said, how would scenarios where the lines between animal and plant are blurred? Say, for example, the plants and the animals of a planet are the same species, but different life stages similar to certain Earth organisms alternating between sexual and asexual generations, except that their generations are a sessile photosynthesizer "plant", that begets mobile heterotroph "animals", which travel away from the parent plant to produce new generations of "plants" later on?

b u f f a l o i d said...

one side effect of strange plant shapes are the evolution of arboreal animals.

on earth monkeys and apes evolved to grasp branches to climb.

but what if the alien plants have no branches?

what if they're like big hollow tubes, or tall flat panels, or cathedral-like land "reefs"?

how would a species evolve to negotiate such an environment?

Sigmund Nastrazzurro said...

Keavan: For some reason it seems more difficult to produce 'unearthly designs' for animals than for plants. The paucity of such designs mmay sugest so, but could also be due to less interest in plants. anyway, I'm trying ;-)
And thanks for the continuingd interest!

Anonymous: I wonder whether such a system would stay that way. If some of the 'hetero-autotrophs' simply went for the fast high-energy route, and specialised in devouring its fellows, they would become animals in all but name; whether there would also be an advantage in going the other way, I do not know.
But as for air plankton, that does not appear feasible on a terretrial planet that resembles Earth: physics conspires against small balloons:

Kevin: That is an interesting idea. There is a group of organisms on Fuaraha that do just that, and at present one painting is devoted to one. At one stage in their lives they are slug-like, and the other stage is plant-like. I have never discussed them much because I always felt uneasy about them. The reason for the uneasy is probably that I do not know whether this makes sense. The big question might be one of relative energy: if you can het enough energy by eating plants to burn energy and move about, does it pay to also have an additional body surfce to produce your won sugar? How large does a photosynthetic surface have to be to support the lifestyle of a lizard, or of a rabbit? There might be an interesting post in that idea...

Buffaloid: interesting, but my post tried to make the point that I saw no way to get plants without them having many small leaves. And with leaves come branches...
Unless an alien photosynthesis is immensely more effective than Earth's, it wil require a large area, and leaves are, I think, almost inescapable to provide that large surface.

tribbetherium said...

To add onto those ideas: if there is a blurring of a distinction between plants and animals, would there also be a blurring of herbivores and carnivores? After all, if the plants and animals are the same species then they're biochemically the same, so a creature that can eat one can eat and digest the other unlike on earth where specialized carnivores can't digest plant matter, for instance.

Anonymous said...

I, Anthony Docimo, do say this:

Never fear - I think I figured out how to have ballonts on Earth/Furaha-like planets.....the requirements are that the ballont's insides generate heat (like shivering bees), and it lives in chilly regions where there is a temperature difference between the ballont's inner cavities and the surrounding air.

Earth plants *used*to* have giant leaves, bedsheet-sized...some of the early tree-looking plants back when animals were first trying to conquer land, were "trees" that would periodically drop the entire branch structure. Each branch was just as much a leaf as it was a branch.

So maybe thats the solution: don't have a strong distinction between leaf and branch, and technically you can have giant bedsheet leaves.

As to mobile photosynthesizers and what to call things that eat them...things like those *do* exist on Earth - just at very small scales (as the youtube channel _Journey to the Microcosmos_ covers quite well across a variety of subjects)

Um, Tribbetherium, just because plants and animals might be the same (species? tough word to pick for, i grant), probably means there will be parts that various species of animal can't eat...think of cheetahs vs vultures in terms of which carnivore eats the bones of the antelopes.

Anonymous said...

(a little more that I forgot to mention)

Looking at your excellent paintings in this post, the first one makes me think a little of a display structure, and-or a kite...and perhaps thats the plant's goal: perhaps the larger leaves grow when its time to "go to seed" as gardeners put it: the superleaves catch the strongest (storm)winds, which pluck it in whole or in part into the air, spreading it to elsewhere...whether it reproduces vegetatively upon landing, or dropping fruits/seeds from the air.

Just a thought.

-Anthony Docimo.

Sigmund Nastrazzurro said...

tribbetherium: again, I doubt that such a situation would remain stable. just as 'more-plantlike' and 'more-animal-like' organisms might soon evolve away from one another, so food specialisation might also occur. As Anthony wrote, a predator doesn't have to eat the whole of an animal. Likewise, most herbivores eat just part of a plant.

-Hydrogen is so light it is difficult to find a better gas for a balloon. Hot hydrogen does have an additional advantage over unheated hydrogen, but it is a tiny one. I have done the maths in the past:
-Do you have a link for the early plants with very large leaves/trunks?
-There are indeed some animals on Earth that have photosynthesis. I will try to find studies looking into how much the photosynthesis contributes to their overall energy balance.
- The shedding of parts of leaves is a very interesting idea. I might use it!

Anonymous said...

re hydrogen and gases - drat; sorry, then. I had hoped to have found a solution so ballonts everywhere wouldn't have to be removed.

I *think* the branch-droppers were these: I could be wrong.

I think I was more referring to mobile photosynthesizing plants/algaes than animals per se, but that works too.

-Anthony Docimo.

Sigmund Nastrazzurro said...

Anthony: I did find some interesting links to small balloons. One appears to have a size that would be very interesting for ballonts:

However: It seems to be physically impossible. Does it actually float up when released? Or is in fact held up by a bit of wire? I have not yet found conclusive evidence.