Sunday, November 8, 2015
(Picture from here.)
There are a number of revolutionary events in the biological history of earth. I've spoken about many of them.
But one extremely large one was the invasion of the land by plants.
We had life in the seas nearly four billion years ago. The most likely origin of life is in the sea unless we were planted here by the Prometheans. However, life on land didn't happen until significantly later. And by life on land, I mean plants. Animals might have ventured on land before then but they didn't stay. Likely the looked around, realized this was a bad idea, and ran/skittled/slithered back to the water before they cooked.
And it was inhospitable. Imagine a bleak bare rock environment. No soil-- that's a product of life. Sure there's sand but soil requires an organic constituent. And without plants that didn't happen. No fungi-- fungi requires decaying organic matter.
There might have been photosynthetic single celled organisms here and there. For example, an algal cell blown up past the water might have landed in a lake and survived. It's not an invasion of the land but it's getting away from the sea.
Even then, it would have been a rough life. The organisms in freshwater lakes also depend on incoming organic material and specific minerals. Much of which happen as a consequence of-- you guessed it-- plants on land.
This was a hard problem.
Consider that nice green algal cell in the ocean.
No problem with water-- it's surrounded by it. It can get all the water it needs. Minerals and organic material? Not a problem: it's in the ocean. Even a billion years ago the ocean was a functioning ecology and a veritable soup of edible organic and inorganic material. All carried by the water. Reproduction? Dump eggs and sperm in the water. The probabilities are that a few will find each other. The water is doing all the work. Radiation? The water stops most of it. Heat and cold? It's going to range from freezing to boiling-- physics prevents anything else. But the temperature is always highly buffered by the mass of water itself. It takes an enormous amount of heat energy to push the water temperature around. (Question: why doesn't global warming happen more quickly? Answer: It's in the water.)
You see a pattern here. Water serves as a wonderful compendium of capabilities: medium of reproduction, temperature and chemical mediator, container of nutrients. Take away the water and what's a poor little algal cell to do?
Plants comprise the kingdom Plantae. All land plants and the green algae are in this kingdom. They are multicellular eukaryotes just like mammals. Unlike mammals-- or any other animal-- plants have have cell walls. The land plants have cell walls of cellulose. Cellulose is just like starch except for how the individual sugars bind to one another. That little difference in binding is the difference between the contents of a potato and the heart of an oak.
Plants photosynthesize-- a feature they share with the red algae and brown algae, which are not part of Plantae but are photosynthesizing eukaryotes.
There are two main divisions in Plantae: the land plants and the green algae. The current presumption is that a species of green algae made its home in fresh water lakes. This would have forced them to evolve mechanisms for coping with the lesser nutrient load, increased radiation load (depending on shallowness) and increased tolerance for temperature and chemical shifts. I.e., it prepared them for land.
This isn't all that far fetched. If you've ever been to a fresh water lake where the level fluctuates regularly, you'll see a band of dried algae at the high water mark. It's black, dried and crusty and looks like nothing more than burnt toast. Toss it in the water and wait a day and you'll get bright green algae.
But it's far cry from that to aforementioned oak. There are a lot of steps between.
The first, obviously, is to be able to operate in a dry, or relatively dry environment.
The land plants are called embryophytes.
Molecular evidence suggests the following clade relationships between living embryophytes:
It's chancy to examine a clade of modern organisms and then attempt to project back in time. For example, humans and chimps share a cladistic relationship: in the great ape family humans and chimps share the most recent common ancestor.
However, that happened several million years ago. Chimps kept evolving since then. All that means, then, is that this common ancestor had shared traits between humans and chimps that evolved over time into humans and chimps. Looking at that last common ancestor, we'd likely expect a blend of traits.
In this cladogram, we would expect the last common ancestor of modern plants branched off to liverworts before it branched off to something else. But that's not the same as saying plants descended from liverworts. Like our chimp example, liverworts have been evolving right along with the rest of plants. The best we can do is examine liverworts and compare them with other modern plants and try to tease out what traits might have been preserved from that ancestor and what traits liverworts evolved on their own.
That said, what's a liverwort?
The Marchantiophyta are bryophyte land plants. Bryophytes consist of mosses, hornworts and liverworts.
They're small, usually less than an inch. If you find a rock in a relatively moist environment you'll probably find lichen-- that flat, gray, leaf-like material-- and liverworts. They have no stems. No leaves. The ones that I've seen look like bits of green clay spread over a rock with a spatula.
They are non-vascular. Vascular plants have tubes inside of them that are used to transport fluid and nutrients-- the plant analog to blood vessels. Liverworts lack this. So it can't get very big.
Liverworts need water to reproduce. They build reproductive structures for their gametes and the gametes have flagella to propel themselves through thin films of water. It's not surprising that they are not prevalent live in excessively dry environments and are not terribly tolerant of direct solar radiation. That rock you found them on was likely shaded. Although, there are desert species.
The liverwort plant body is called a thallus-- interestingly enough, the same term is used in describing algae and fungi. It's anchored to the ground by a rhizoid. Rhizoids can be as little as one cell across and are hair like. Since the liverwort lacks vascularization, diffusion of nutrients, oxygen and waste products has to be across cells. Hence, it's thin. It's outer skin is often covered with a waxy material called cutin to protect it from drying out. Liverworts lack lignin, the main support polymer of vascular plants, so it can't get very tall.
In short, the liverwort does pretty much the bare minimum to survive on land. It looks as if a green algae thought of the cheapest and easiest ways to survive on land and implemented them. It's a long way from a liverwort to our towering oak. Still, it's a step in the right direction.
It's not hard to imagine liverworts (or something like them) in the shade of a boulder a few feet from a lake, in a lonely and barren world, bare rock in all directions.
The liverwort doesn't care. It's got a foothold.
Early evolution of plant evolution
Invasion of the land by plants: when and where?
Climate change caused by land plant invasion
Sunday, November 1, 2015
(Picture from here.)
Yeah, another State of the Farm. We're still in harvest season. It tasks me. I shall have it.
I've complained about this year's weather before and, truth be told, we did not get the amount of garden produce we wanted. Potatoes, not so great. Tomatoes were a joke. Beans and cold crops ended up lunch for a woodchuck.
I mean we did have enough garden crops to enjoy many good meals. We have some beans in the basement. But we didn't have what one would call abundance.
Not from the garden, anyway.
Much of our tree harvest-- chestnuts, peaches, cornelian cherries and persimmons-- were quite good.Which brings us to the problem of abundance.
Getting beans, tomatoes or plums here and there adds spice to the table. But harvest has to cope with the problem of scale.
For example, let us consider the chestnut.
The native American chestnut is all but wiped out by the chestnut blight-- a nasty fungus brought over to us from Japan. The chestnut ranged from north Alabama to Vermont. It was a climax tree and supplied food to native Americans and wood to colonists. In Italy, chestnut flour in some places was a more important staple than wheat flour. The blight changed all that.
What we have now are hybrids of various sorts between Chinese chestnut and American chestnuts or pure Chinese chestnuts. Resistant strains have been developed and it is possible that someday the American Chestnut will return in force. I hope for that. I hope for the return of the American Elm, as well.
We have three trees on our property. Until this year, we didn't have a mature enough pair to get a good yield. This year we went from a pound or two to somewhere between thirty and sixty pounds. This is several hundred chestnuts.
If you look at the picture at the top, you'll notice a vicious looking burr and brown nuts. The spikes on a burr will penetrate most leather gloves. It has to be removed.
The brown on the remaining nuts is a sheath. Most people boil the nuts in some way to loosen the sheath. That's okay for a few but isn't practical for hundreds. What we do is puncture the sheath and microwave them. This loosens the brown sheath so it can be removed with a paring knife.
Not shown in the picture is the papery covering underneath. We dry the nuts and then remove the papery covering. Then, we vacuum seal them and store them in the basement.
This process isn't so bad for a pound or two. But we've been skinning burs for a couple of weeks now.
In previous years, we've used it in soups. I'm not sure how many dried chestnuts we have but it is north of twenty pounds. Clearly, we'll be discovering new uses for it.
My point is that the scale of harvest is meaningful. Every gardener has a zucchini story where they kept on coming like it was the zombie apocalypse. It's a painful experience. Here is the very earth providing you with more than you asked for. The compulsion to make use of it is overwhelming. I remember one place I worked where the break room had three large zucchinis on the table labeled "free", every Monday throughout the month of August.
But we'll manage the chestnuts. Grind them into flour like the Italians did.
A bigger problem for us this year was fruit. Specifically: peaches, grapes and persimmons.
The peach harvest was in the tens of pounds. Cut 'em up and put them in the freezer. Then the grapes came in-- somewhere around sixty pounds of Concords and about twenty pounds of Marechal Fochs. Twenty pounds isn't that much for the M/F's. The grapes are small and the bunches compact. I intended them for wine so I wait until I have about thirty to forty pounds and then it's into the press.
The Concords are a different problem.
The Concords loved this weather. This is the greatest yield we've ever had. All from one vine. But the Concords have always had a fairly good yield. This year was exceptional but perhaps as much for the low numbers of yellow jackets as anything else. In previous years, I've had to fight them for the grapes. About the time they come in the wasps start looking for a good food source for the winter.
I blended in the Concord to the M/F in the wine making and it worked pretty well. But then the harvest became too much.
I don't really like the taste of dried grapes and getting rid of the seeds is a problem. In addition, there are only so many grapes one can eat either directly or in the form of jam. I considered making a grape syrup similar to maple syrup but that turned out to be a shortcut back to jelly.
So, about fifteen years ago, I started an earnest journey to make a good, dry Concord wine. It took about ten years. I have technique and recipe, which I'll talk about in the future, but this post is already too long. Suffice to say, forty pounds of Concord grapes can be spun into six gallons of a nice blush wine. Much easier to store. But the steps are still a scale issue:
- Harvest the grapes.
- Pull the grapes off the stem.
- Freeze them.
- Thaw and press.
- Make wine-- it's own set of steps.
Abundance is a fact of nature-- we're not the only ones that take advantage of it. All organisms produce more offspring than are strictly needed to allow for attrition. Cod lay up to 500,000 eggs/kg of body weight. Our two chestnuts provided us with hundreds of potential offspring. The natural systems presume predation on offspring and produce accordingly. In this context, we're the predators. Others, like commercial bananas, depend completely on us to propagate them. The supermarket banana will not sprout on its own.
On our little farm, we're interrupting the chestnut reproductive cycle, preventing them from recolonizing the northeast for our own selfish purposes.
Makes me want to laugh like a super villain.
Ha ha! Castanea dentata! Foiled you again!Gives you something to do when you're pulling off burrs.
Oh, please. Let me propagate and become a climax forest species again. I'll do anything you ask.
Never! You had your chance! Now it is the turn of the oaks and the maples.