Announcements

• For biotechnology lab– Labelling GUS stained seedlings– Hyperladder

• For water status lab 1– Measurement of relative water content

Water Status Lab IIWater Status Lab II

Stomatal opening

23.14 Simplified model for ABA signaling in stomatal guard cells

ABA mediated stomatal closure mechanism:

Water deficit → ABA → stomatal closureABA → ROS → Ca2+↑ → Cl- efflux/membrane potential depolarization → K+ efflux/K+ influx is blocked → ψp decrease/water loss → volume reduction → stomatal closure

ABA → NO/S1P → cADP ribose/IP3 → Ca2+ → pm H+-ATPase inhibited → H+ gradient dissipation (pH) → K+ efflux

w/o ABA & w/ ABAw/o ABA & w/ ABA