1. 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

2. is still active for long-term responses enantiomer

3. ABA assay: Gas chromatography (10 -13 g) High-performance liquid chromatography Immunoassy

4. ABA biosynthesis takes place in chloroplast and other plastids direct pathway

5. 9-cis-epoxy-carotenoid dioxygenase (NCED), is rapidly induced by water stress, in thylakoid

6. MW 264 ABA glucoside

7. 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

8. * 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