EFFECT OF AQUEOUS SO2 INCUBATION ON STOMATAL BEHAVIOUR OF THE LEAF EPIDERMAL STRIPS OF CAJANUS CAJAN (L.) MILLSPAUGH AND AMARANTHUS PANICULATUS (L.)
B. Priyadarshini, A. Satya Gowri Parvathi, B. Sujatha* and J. Saraswathi
The widespread use of coal and petroleum as energy sources for industries has led to the emission of large quantities of sulphur dioxide (SO2) into the atmosphere. Sulphur dioxide is a gaseous pollutant widely diffused in the world today. The stomatal behaviour of Cajanus cajan and Amaranthus paniculatus under aqueous SO2 exposure were studied in isolated epidermal strips of their abaxial leaf surfaces. After exposed to illumination for 1 h, the strips were transferred to small petri dishes (5 cm) containing 0, 10, 20, 30, 40, 50, 100 and 250 ppm aqueous SO2 solutions. Stomatal aperture size was measured at regular time intervals under a compound microscope using precalibrated occular micrometer. The lower aqueous SO2 concentrations initially increased the stomatal opening, followed by a closure with increasing duration of SO2 exposure that was responsible for the stomatal opening differs in pigeonpea and amaranth. The distribution of potassium in the guard cells was detected by histochemical technique. In pigeonpea, aqueous SO2 indicated that the guard cells of control and 10 ppm SO2 treated epidermal strips exhibited higher quantities of potassium accumulation than the guard cells exposed to higher concentrations of SO2. On the other hand, in amaranth the guard cells of control epidermal strips showed higher potassium levels than SO2 treated ones at 2 h of incubation. Further the data indicated that amaranth appears to be more sensitive to SO2 than pigeonpea.