The Physiology of Flowering Plants - KHAM PHA MOI

WATER-DEFICIT STRESS 351Ψ or Ψ π 10 –1 Mpa0–8ΨΨ πΨ pFig: 13:3 Generalizedrelationships between waterpotential C, osmotic potential C pand relative water content in leavesof herbaceous crop plants; 100%water content represents themaximum the tissue can hold, andmaximal turgidity. The length of thearrows equals the turgor pressureC p , which can be seen to decreaserapidly in the early stages of waterloss: over the first 5% loss in watercontent, the C p has halved. Adaptedfrom Hsiao et al. (1976).–16 60 80 100Relative water content (%)Fig: 13:4 Summary of the mainevents in development of waterstress resistance. The perception ofstress initiates signal transductionchains leading to the synthesis ofproteins. These include enzymes forsynthesis of ABA, which can thenactivate other genes. The newproteins, or their products,counteract (upward arrows)deleterious effects of water stressnoted at the top of the diagram.ROS = reactive oxygen species.