RECOVERY OF LEAF ELONGATION DURING SHORT TERM OSMOTIC STRESS CORRELATES WITH OSMOTIC ADJUSTMENT AND CELL TURGOR RESTORATION IN DIFFERENT DURUM WHEAT CULTIVARS

In order to investigate the responses of leaf elongation rate (LER), turgor and osmotic adjustment (OA) during a short-term stress (7 hours) imposed by PEG(6000) and a recovery phase, three durum wheat (Triticum durum L.) varieties [Inrat; MBB; and OZ] were grown in aerated nutrient solutions. Leaf elongation kinetics of leaf 3 was estimated using LVDT. Turgor was estimated using a cell pressure probe; osmotic potential as well as total sugars and potassium (K+) concentrations were estimated from expressed sap of elongation zone. Growth recovered rapidly and then stabilised at a lower value. A significant difference was found in % recovery of LER between the varieties. The cessation of growth after stress coincided with a decrease in turgor followed by a recovery period reaching control values in MBB and Inrat. A strong correlation (R-2 = 0.83) between the reduction in turgor (A turgor) and % recovery of LER was found at 7 hours after stress. The difference in the partial recovery of LER between varieties was thus related to the capacity of partial turgor recovery. Partial turgor recovery is associated with sugar or K+ based OA which indicates its importance in maintaining high LER values under water deficit.