Osmotic and Ionic Effect of Naci on Growth, Physiological and Biochemical Responses of Phragmiteskarka

Salt stress is known to hamper steady state water flow which may reduce plant growth.This research was aimed to study the roles of leaf turgor, osmotic adjustment and cell wall elasticity under saline conditions which may reduce biomass production in Phragmites karka (a marsh grass). Plants were grown in 0, 100 and 300 mM NaCl and harvested on 3, 7, 15 and 30 days to observe periodic changes in growth and water relations. Leaf number, relative growth rate, and relative elongation rate were higher in the non-saline control than in the plants grown under saline conditions. Plants showed a rapid decline in leaf growth rate (7-15 days) in 300 mM NaCl compared to a delayed response (15-30 days) in 100 mM NaCl. Leaf water potential (ΨW) decreased with increases in salinity after 3rd day while osmotic potential decreased after 15th day. Low leaf turgor (Ψp) on the 3rd day indicated an initial phase of osmotic stress under saline conditions. Plants maintained higher Ψp in 0 and 100 mM than in 300 mM NaCl. Differences between mid-day and pre-dawn ΨW and water saturation deficit were higher in 300 mM NaCl than with other treatments. Water potential and hydraulic capacitance at turgor loss point decreased while bulk elastic modulus (Ɛ) increased in 300 mM NaCl. Maintenance of turgor and growth at 100 mM NaCl could be related to efficient osmotic adjustment (use of K+ and Cl-), higher water use efficiency, and lower Ɛ while poor growth at 300 mM NaCl may have been a consequence of low turgor, higher Ɛ and decreased cell hydraulic capacitance.