PHOTOSYNTHESIS, WATER RELATIONS AND LEAF GROWTH OF CUCUMBER EXPOSED TO SALT STRESS

Cucumber (Cucumis sativus L., hybrid 'Pepinex') was grown in soil cult ure over a range of NaCl concentrations (0-190 mM) in a glasshouse and the effects on gas exchange, water relations, ion content and leaf gr owth were examined. Salinity at 8.5 mM had no effect on plant performa nce, but exposure to higher salinities (25, 50, 120 and 190 mM) caused stomatal closure and a significant decrease in photosynthetic rate. L eaf water potential, osmotic potential and turgor potential were also lower with increasing salinization. Leaf expansion rate and final leaf size declined linearly with an increase in external NaCl. These diffe rences were associated with 22%, 49% and 80% reduction in relative gro wth rate. The results suggest that salinity influences cucumber growth through a reduction in photosynthesis and photosynthesizing area.