Tara Jawahar
Summary
Researchers at Brown University have been analyzing the cells of two clades of grass (called BED and PACMAD). A clade is a "group of organisms classified together [because] of homologous features traced to a common ancestor" (Dictionary.com). These species are already closely related and were observed to see how efficiently they photosynthesized.
It was discovered that the PACMD clade of grass had its vascular structures closer together and also had a tighter outer covering on the veins that carry food, water, and carbon dioxide for the plant. Therefore, when there is not much available carbon dioxide, the veins efficiently bring carbon dioxide without losing it through the veins. The bigger, orange circles in the picture below are the veins, and the "bundle sheath" cells are the smaller rings around each circle. There are more "bundle sheath" cells surrounding the veins, providing it extra protection.
Relevance to Class
Over the course of the past couple weeks, we have been learning in-depth about evolution. Both these species are clades, meaning they have evolved from a common ancestor, a topic we have studied. About 60 million years ago, the speciation of this type of grass led to these different species of grass that can be found today. We also studied the theory of natural selection extensively, which is evident in the way these species of grass have evolved separately. One of the species, the PACMAD species, probably gradually evolved to have the special features that makes it photosynthesize more efficiently today. This adaptation helps the plant use the carbon dioxide after the atmospheric carbon dioxide decreased millions of years after the two clades diverged.
Another connection to the class curriculum is the topic of plants and photosynthesis, which we learned about earlier this year. The functions of the veins and the importance of carbon dioxide to the plant help to better understand why this adaptation in plants is helpful.
URL: http://www.redorbit.com/news/science/1112754003/photosynthesis-evolution-grass-clades-122612/
Author: Brett Smith
Date of Publication: December 26, 2012
Do all types of grass have a relatively recent common ancestor and can be considered as part of the same clade?
ReplyDeleteWhat is a "bundle sheath" cell?
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