「植物看得見你」公開課筆記／3.1 Plant Cells

Plants sense their own odors and even the odors of their neighbors. Plants know when their fruit is ripe, they know when their neighbor is being eaten by hungry bugs, because they can smell it. There are even plants that can differentiate between the smell of a tomato and the smell of wheat.

When it comes to smell, a plant's range is rather limited and it is much less than what humans have. But a plant's sense of smell is still highly sensitive. And it communicates a great deal of information about both the environment and the plant's physiology.

Plant Cell Biology

Cells are the smallest basic unit of life. It can divide and transfer genetic material to further generations, independent of any other cells touching them necessarily. While all cells have similar characteristics, each cell type is unique, which then gives each type of tissue its own characteristics. For example, liver cells make a liver. Insulin-making cells make the pancreas. Skin cells protect our bodies. Just like a leaf cell in a plant is different than a root cell.

There are very few cells that we can see with the naked eye, for example a frog egg. For eukaryotic cells, plants and animal cells, it's enough to use a light microscope.

Historically, the first microscope built was in the 17th century. The first cells detected were in a plant (cork). Robert Hook built the first microscope. It could magnify tissues about 15 times. He didn't understand or comprehend that all the big organisms were made of cells. He thought it was specific for cork.

All cells, whether plant cells or animal cells, are basically like a bag of liquid where you have an outer membrane which encloses a soluble interior. Within the inside of the cell, we can find the nucleus which has the DNA, the hereditary material. Other small parts of the cell, organelles, such as the mitochondria, which makes energy.

So a cell is the outer membrane, which is called the plasma membrane and the inner parts -- the cytoplasm. This is to both for a animal cell and for a plant cell.

But a plant cell has a few other organelles. For example all plant cells have outside of the plasma membrane, a structure which we call the cell wall. The cell wall is what gives a plant its structure in lieu of a bony skeleton. All plant cells are first a cell wall, which bounds the cell membrane, which holds the cytoplasm. Now, the membrane and the cytoplasm together, we call a protoplast.

Plant cells also contain the few other organelles. One being the plastids, of which the best example, is the chloroplast. This is the organelle which makes energy through photosynthesis. Turning sunlight into energy.

And there's another organelle called the central vacuole. This is a balloon, within a balloon. That is basically a type of warehouse for the plant.

A membrane is basically a phospholipid. It's a type of fat which has a polar side, a part that has a charge, which is next to the soluble part either outside or inside the cell, and a lipid which is apolar, which is hydrophobic, which doesn't allow water to pass, which is on the inside of the membrane. Or these phospholipids associate together, and they form a protective covering which encases the entire cell. We see things that are similar to membranes formed, for example, by fat on chicken soup, or when a soap bubble is made, these are, again, hydrophobic molecules which associate into small circles, into small balloons.

Within the membranes, there can be different types of proteins, which often characterize what type of cell there are. These are proteins that are often involved in signaling information from inside to the out. There are proteins which can be bound only on the inside. And there are proteins which could be bound only on the outside. There are also other examples of molecules which could be found within the membranes, for example, such as cholesterol in animals but all membranes basically have this same structure.