9. Stress physiology of forest trees: The role of plant growth regulators

Abstract

Abiotic and biotic stresses elicit changes in normal physiology of trees . Plant growth regulators (PGR) are involved in the stress response and appear to have two roles : 1) to minimize the impact of the stress on the tree and ; 2) to trigger stress resistance mechanisms . In the latter case the PGR-induced changes appear to enhance resistance to subsequent stress . This cross-adaptation to stress is important in trees .The role of PGRs in the physiological response to the abiotic stresses of water deficit, water excess, temperature, nutrition and mechanical perturbation is discussed along with cross-adaptation in the interactions of these stresses . Disease response and defense, and plant-plant communications involve PGRs and are topics covered with respect to biotic stress . Stress leads to early senescence and abscission in trees . These processes are controlled by PGRs and are briefly discussed .