Plant Physiology -- 04/20/11

Lecture 4-5


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How did anybody figure this day length/night length thing out?


What is the pattern?


Examples of plants and their critical periods (the time they are waiting for)


Why is one plant a LDP, another a SDP, another DN?


So how does the plant measure the length of the light period?


How can we figure out problems?


To solve a particular problem


Examples with real plants:


OK, so how does phytochrome work to determine flowering?


What do we know about light perception?


What do we know about how the light signal cause a change in gene expression?


How does the differentiation lead to flowering and other differentiation?


What does phytochrome look like?


What light does phytochrome absorb?


Reminder: phytochrome molecules can be in one of two forms, interconvertable


How do the two forms interconvert?


What happens in the dark?


Does it work this way with all plants, and all the time?


What happens if we give some light in the middle of the night?


Is this all there is for phytochrome and its responses? NO


So we have looked at how plants can use R and FR light to tell them about their light environment. With this system they can detect an overstory, neighbors, or the length of the day, or tell if they are near the surface of the soil, and act appropriately.

There is another major light detection system, which uses blue light but does not respond to red/far red. We call this the non-phytochrome blue system.


What things are controlled by blue light?


What absorbs blue light in the cell?


Phytochrome and the cryptochrome (true blue) receptors are used just for information.


How do we know that a blue response is due to the true blue receptor, and not phytochrome?


What are some growth & movement responses to blue light?


How does blue light relate to photosynthesis?


Is there a single blue light receptor?


End of the section on light as information.