「植物看得見你」公開課筆記／1.5 Major Themes in Plant Biology

Hierarchy of Organization

On all levels of biology and plant biology, we see hierarchy. We can look at the individual cell, break the cell down, and see what the cell is made of. Or we could put the cell together to make organs such as leaves, put the leaves and the trunks together to make a plant, or even have a complete ecosystem. At each level we can learn something new about how the plant works.

The cell is the basic structure of plant biology and all biology. A lot of what we understand how a plant works, we understand by understanding how a plant cell works.

Evolution & DNA

To understand that what we see in modern plants is a result of their genes. It's a result of changes through evolution.

In each of these levels, what we call structure and function. For example, if we look at a leaf, what's it's function? I think we all know the function of the leaf is to absorb the light, the energy that a plant needs for photosynthesis. What's it's structure? It's flat, in order to absorb all that light.

But what's the structure of a leaf in a cactus? It is a thorn, it has a different structure, because its function is different. It doesn't want to lose water, so it minimalised its leaf and try to conserve area. It is the selection through evolution to the modern forms of plants that we see.

Interaction between the individual and its environment

When we see a plant / a tree in its ecosystem, we'll learn about how plants communicate, interact, plant, one plant to a second plant.

There could be communication between individuals, leaves, cells, or parts of cells. So at each level, there's an interaction between the individual and its environment.

Huge Amount of Diversity

All of these flowers are formed by the same basic genes, but slight changes in how they are regulated gives us this beautiful diversity of plant biology. But because the genetic basis of flower development is the same, we see a unity in plant form and plant biology. Now in this course we cannot deal with all types of plants, but what we are going to learn about will be true for let's say 95% of them, because of this unity.

Selected Pressures

You cannot understand biology without understanding evolution. The modern form of a plant really shows how the plant evolved through millions of years of selective pressures.

But not only have selected pressures affected plants, human pressures have selected plants. e.g. Wild mustard grows in fields in many parts of the world, where broccoli, cauliflower, kale, brussels sprouts and other brassica vegetables evolved from it due to the intervention of humans.

Actually genetically, broccoli, cauliflower and wild mustard are essentially identical, slight changes in one or two genes. Actually in the lab, we can take a model plant that's like wild mustard and by changing one gene, cause it to make little broccolis at its end. You could get a huge change in form, by a very slight change in the DNA.