effect of water stress induced by polyethylene glycol on stomata and photosynthesis in lupinus termis plants

ABSTRACT

Lupinus termis plants were grown in solution cultures supplemented with polyethylene glycol [6000] to maintain osmotic potentials ranging from -0.5 to -1.0 MPa. Stomatal number, stomatal opening, leaf pigments, photosystem II activity and 14 CO2- fixation were measured at three successive stages during the vegetative period of plant growth. Changes in the stomatal number and in the area of stomatal openings were found to depend on the level of the osmotic potential and not on the stage of plant growth. The obtained inhibition chloroplast activity and in 14 CO2- fixation were accompanied by either stomatal closure [at -0.075 MPa] or stomatal closure and inhibition of chlorophyll synthesis [at -1.0 MPa] during all stages of plant growth. Thus, chlorophyll content appeared to increase [at -0.5 MP], to decrease [at -1.0 MP] and not to change [at -0.75 MPa] in relation to control levels. A reverse situation was, in general, observed for the content of carotenoids