Plastids in general November 14, 2015 22:38
Our Dynamic Cell Models kit includes chloroplasts, chromoplasts, and amyloplasts. So I find that we end up explaining about the different types of plastids at meetings when we show our Dynamic Cell Models. Most teachers never specifically studied plants, so they never had a way to learn about plastids. Usually they find them pretty cool. I was a neuroscience major, so I only learned about plastids after I started teaching. Most biology books don't even mention plastids other than chloroplasts, so it can be difficult to get introductory information about them.
The plant zygote has a proplastid that it gets from the female gamete. As the plant embryo divides and cells differentiate, the proplastid differentiates into whichever plastid is needed in the cell it is found in. So, if the cell is a green leaf cell, the plastid differentiates into a chloroplast. But if the cell is in a root, for example, there's no point in the proplastid becoming a chloroplast because no sunlight reaches it. Some cells in this situation develop amyloplasts, to store starch. Meanwhile, if the cell ends up in a part of a plant that should have a color other than green, like a fruit or a flower, the proplastid can differentiate into a chromoplast, to make pigment.
With all this differentiation information, I hope you can see that plastids are a great differentiation lesson in a high school classroom (NGSS puts it in high school, but it could be at any level).
Future blog posts:
- plant cells are the ultimate stem cells
- plastids make for great de-differentiation and re-differentiation
- some pigments are inside plastids while others are not...