Hormonal interactions and stomatal responses
. (2003)
– . Journal of Plant Growth Regulators 22: 32–46. –
http://plantcellbiology.masters.grkraj.org/html/Plant_Growth_And_Development4-Plant_Hormones-Gibberellins_files/image001.gif
Both environmental and hormonal factors and their interactions affect stomatal behavior. Methodologies for identifying hormonal interactions affecting stomatal function are reviewed.
Although there is abundant evidence that abscisic acid (ABA) closes stomata, evidence that the other classical plant hormones (auxins, cytokinins, ethylene, gibberellins) in isolation alter stomatal response often comes from exogenous applications to detached epidermis and leaves, rather than correlation of endogenous concns. with stomatal conductance (gs).
Evidence for hormonal interactions comes from isolated tissues with exogenous hormones supplied at nonphysiol. concns., or from variation in stomatal response to xylem ABA concentration in planta.
The roles of hormonal changes in causing stomatal closure following changes in soil environment are considered. Although soil drying induces multiple changes in xylem sap composition, anal. of stomatal responses suggests a dominant role for increased endogenous ABA concns. and relatively little evidence of roles for other hormones.
A similar picture emerges from studies of soil compaction. Although soil flooding decreases ABA export from the root system, there is some evidence that apoplastic ABA accumulation elicits stomatal closure.
Stomatal closure following nitrogen deprivation does not appear to involve ABA and may provide a suitable exptl. system to investigate roles for other hormones. The availability of mutant or transgenic lines with altered hormone homeostasis or sensitivity provides opportunities to screen for altered stomatal behavior in response to different environments, and may provide new evidence that hormonal interactions are important in the control of stomatal behavior.
PLANT STOMATA ENCYCLOPEDIA 
