Abcission Flashcards
1
Q
What are abiotic factors?
A
non-living chemical and physical parts of the enviornment
2
Q
Why does abcission occur in deciduous plants?
A
- amount of glucose required for respiiration to maintain the leaves and anti-freeze chemical is greater than the amount produced by photosynthesis
- in time of low sunlight and temperatures
- trees that are in leave are more vulnerable to damage or being blown over
- lose leaves in winter and lay dormant until days and temperatures rise
3
Q
How are plants sensitive to day length?
A
- results from a light-sensitive pigment called phytochrome
- exists in 2 forms - Pr and Pfr
- each absorbs a different type of light
- and the ratio of the 2 forms changes depending on the level of light
4
Q
What does the falling light level result in?
A
- falling conc of auxin
5
Q
How do plants respond to the falling auxin conc?
A
by producing gaseous hormone ethene
6
Q
What is the abcission zone?
A
- 2 layers of cells sensitive to ethene
7
Q
What does ethene do?
A
- initiate gene switching in these cells resulting in the production of new enzymes
8
Q
What is the purpose of the enzymes ?
A
- digest and weaken the cell walls in the outer layer of the abcission zone, known as the separation layer
9
Q
What are the other events during abcission?
A
- vascular bundles sealed off at leaf
- fatty material deposited in the cells on the stem side of the separation
- forms a protective scare when the leaf forms
- cells deep in sepparation zone respond to hormonal cues by retaining water and swelling
- puutting more strain on the already weakend outer layer