They say that in order to predict the future, one must understand the past. With that in mind, we decided to look way back to how plants existed in prehistoric times.
Now, we like to consider ourselves cultivation experts, but to carry out this task we needed to get in touch with a different kind of plant professional. Enter Dr. Ian Miller, curator of paleobotany at the Denver Museum of Nature and Science.
Paleobotany is the study of the evolution of plants. You have the prefix paleo, just like paleontologist who dig up dinosaur bones. Then you have botany, the study of plants. Dr. Miller provided us with some fascinating info about where our plants come from, and how and why they do what they do.
“Plants are these organisms that evolved about 420 million years ago,” he says. “They evolved from green algae, and then they were all terrestrial. Some plants have moved back to an aquatic environment, but the first plants were all on land.”
Dr. Miller also tells us the evolution from water to dry land is responsible for many of the features we find in plants today. Life on land is quite different from life in the water, so plants had to make some changes to survive.
First, they had to retain moisture on dry land, hence the development of waxy leaves. Next came spores and pollen, allowing for dispersal via wind. Much in the way lungs replaced gills in land animals, plants developed stomata to exchange gases with the environment. Finally, plants developed roots to gather moisture and nutrients from the ground, and vascular systems to move the water up through their bodies.
Those five amazing evolutionary changes allowed plants to successfully colonize land. But that was a long time ago, so how have plants changed in the 420 million years since?
“In their evolutionary history, from [420 million years ago] until today, they basically only do three more things: make wood, make seeds and make flowers,” says Dr. Miller. “There are many, many other smaller evolutionary advances, but you can think of those three as the other major advances that are in line with the first five.”
The first plants were relatively diminutive, with the largest measuring perhaps six feet tall. Once plants developed wooden structures, they could become durable trees, which are built for a long life span. Trees aren’t usually the type of plant life that growers are most interested in, so we won’t talk much about wood. However, the evolution of seeds speaks to more familiar hydroponic grower territory.
“Seeds are this amazing advantage,” Miller says, “because before that plants didn’t protect their embryos, and the seeds protect those fertilized new plants.”
That brings us to the element of plant growth that we growers are most interested in: the flowers our plants produce.
“The flower is the final step,” Miller explains. “Today 95% of all living plant species have flowers. The flower evolved about 130 million years ago, so there’s this incredible time between 420 million and 130 million years ago – almost 300 million years of plant history – where plants have no flowers. So the flower is a relatively recent evolutionary event.”
That event changed everything. Once the flower arrived, those flowering species became dominant, covering most of the earth. How did flowering species win in this Darwinian competition? One of the big reasons for their massive success is double fertilization.
“Double fertilization allows for the endosperm,” explains Dr. Miller, referring to the unique process by which angiosperms (flowering plants) use multiple sets of chromosomes to form both a new plant embryo, as well as surrounding endosperm, which creates starch, oils and proteins for the embryo (and other herbivores) to feed on. “That’s the stuff of corn and nuts,” he continues. “The high-energy tissues that allow seedling plants to get their jumpstart. That speeds up their reproductive cycle drastically.”
Here’s where we growers start to become especially interested. It takes more than a year for a gymnosperm (plants that don’t produce flowers) like a pine tree to reproduce, whereas some flowering plants can reproduce in mere weeks, which is a huge advantage, especially for growers who like to maintain a perpetual harvest cycle.
Another feature of early plant life is that those plants lived in a different environment than the one that exists today. For example, carbon dioxide levels were much higher in the time of the dinosaurs due to extensive volcanic activity. Active volcanoes pumped the atmosphere full of CO2, making for a denser atmosphere.
That dense atmosphere also meant increased temperatures. While the climate around the equator was probably much like it is today, the tropics extended much farther north and south. In fact, there was lush vegetation extending almost to the poles.
These increased temperatures may have meant that organic matter decomposed more quickly. However, it’s not clear whether that made the earth more fertile for plant life.
As growers, these kinds of questions intrigue us. After all, it’s all about bigger and faster for us. We want quick growth periods and huge fruits. Naturally that fact had us wondering if there were giant flowering plants in the earth’s history – the type of thing that could satisfy a grazing behemoth like the brachiosaurus, for example. If there were, maybe there’s something we could glean from growing conditions in the past and reproduce controlled growing environment, thereby allowing growers to produce giants plants of our own.
Alas, that’s not the case. In fact, flowering plants have been roughly the same size since they first came into existence. So much for producing enormous apatosaurus strains in our grow room.
Still, we learned some really cool things from this lesson in paleobotany, including the fact that, as growers, all we really endeavor to accomplish is to help our plants do what they have naturally been trying to do for millennia.
“You’re really playing to what a flowering plant wants to be,” Dr. Miller tells us. “They want to get big and grow fast. They’re not saving their resources. They want to reproduce as fast as possible. They’re in no way storing any fertilizer or nutrients, saving it for the winter; they fully expect to be dead.”
That’s fine by us. Once they’ve grown a maximum amount of tasty fruits, we’re happy to play grim reaper to our plants. We’ll harvest and cure our goods, and then start another crop of angiosperms on their way through the cycle they’ve perfected over 420 million years.
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Thursday, 28 February 2013