Spatial distributions of inorganic ions and sugars contributing to osmotic adjustment in the elongating wheat leaf under saline soil conditions

Abstract

In this study, we quantified the spatial distributions of inorganic ions and sugars contributing to osmotic adjustment and their net deposition rates in the elongating and mature zones of leaf 4 of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in growth chambers in soil irrigated/treated with nutrient solution containing either no added or 120 mM NaCl. The sampling was conducted on the 3rd day after emergence of leaf 4 at 3 and 13 h into the 16 h photoperiod. The patterns of spatial distributions of total osmoticum, cation, anion and sugar contents (mmol kg-1 H2O) were distinct and were affected by salinity. The total osmoticum content in the region between 0 and 60 mm above the leaf base differed between the two harvests at 120 mM NaCl. Net deposition rates of total osmotica, cations, anions, and sugars (mmol kg-1 H2O h-1) in both treatments increased from the base of the leaf to the most actively elongating location and then decreased near the end of the elongation zone. Contributions of cations, anions, and sugars to osmotic adjustment varied with distance from the leaf base, and were about 21–30, 15–21, and 13%, respectively, in the elongation zone. We suggest that the accumulation of solutes under saline conditions occurs both by increasing the net deposition rate of osmotica and by reducing growth.