chapter 23 abscisic acid (aba): ¤ a seed maturation dormin: a growth inhibitor was purified from...
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Chapter 23 Abscisic acid (ABA): ¤ a seed maturation
dormin: a growth inhibitor was purified from sycamore leaves collected in
early autumn, when the trees were entering dormancy
long-term development: the change of gene expression
abscisin Ⅱ a substance that promotes the abscission of cotton fruits [Ironically] ABA-induced abscission of cotton fruits is due to ABA’s ability to stimulate ethylene production
ABA appears to promote senescence (the events preceding abscission)
¤ antistress signal
inhibit growth and stomatal opening, particularly when the plant is
under environmental stress
short-term development: the alternation of ion flux across membranes
is still active for long-term responses
enantiomer
ABA assay: Gas chromatography (10-13 g) High-performance liquid chromatography Immunoassy
ABA biosynthesis takes place in chloroplast and other plastids
direct pathway
9-cis-epoxy-carotenoid dioxygenase (NCED), is rapidly induced by waterstress, in thylakoid
MW 264
ABA glucoside
ABA-deficient mutants: can be corrected by the application of exogenous ABA.
ABA-deficient vp14 mutant:
vp: maize mutant
Vivipary (preharvest sprouting):
precocious germination of seeds in
the fruits
* ABA is transported by both the xylem and the phloem, but rich in phloem
sap
* ABA synthesized in the roots can be transported to the shoot via the xylem
* ABA acts as a root signal that helps reduce the transpiration rate by
closing stomata in leaves
* Stomatal conductance is often much more closely related to soil water
status than to leaf water status, and the only plant part that can be
directly affected by soil water status is the root system. (p.675R)
* ABA redistribution – “anion trap” concept
the steepness of the pH gradients across membrane
the specific uptake carriers