Kinetics and spatial distribution of leaf elongation of wheat (Triticum aestivum L.) under saline soil conditions

Leaf development of wheat largely determines the rate of plant growth in th e early growth stages and is most sensitive to salinity. The objectives wer e to investigate the shoot growth, area of leaves, and kinetics of leaf elo ngation of wheat seedlings (Triticum aestivum L.) grown in illitic-chloriti c silt loam with four salinity levels from 0 to 120 mM NaCl in growth chamb ers. Shoot fresh mass (FM) and leaf area were measured at days 12 and 18 af ter sowing. Instantaneous measurements of the leaf elongation rate (LER) of leaves 3, 4, and 5 of the main stem were carried out by using linear varia ble differential transducers (LVDT). Spatial distribution of relative eleme ntal growth rate (REGR) and the length of the leaf elongation zone were det ermined by measuring displacement rates with a pricking method. Shoot FM pe r plant linearly decreased with increasing salinity levels. Leaf area under saline conditions was significantly correlated to the shoot FM during vege tative stages, indicating that leaf growth most sensitively responds to sal inity. Salinity delayed leaf emergence and affected leaf growth longitudina lly and laterally. Reduction in the final length of leaves 3, 4, and 5 was mainly a result of a decrease in their LER. The decreased LER under saline conditions was more pronounced during the steady growth phase and during th e light period compared to later stages and to the dark period, respectivel y. Salinity affected the LER more severely with increasing leaf number, pro bably as a result of the longer exposure to salinity and longer elongation zones for higher leaf numbers. The reduction in LER resulted from decreasin g the REGR but did not result from shortening the length of the leaf elonga tion zone during the linear phase of leaf growth.