Foliar application of 5-aminolevulinic acid alleviated high temperature and drought stresses on wheat plants at seedling stage

Wheat (Triticum aestivum L.) seedling establishment is very sensitive to temperature and drought stresses. The present study was conducted to investigate the effects of foliar exogenous 5-aminolevulinic acid (5-ALA) application on wheat seedling under different temperature (25, 30, and 35 degrees C) and water regimes (normal and 65% watering). Five different levels of 5-ALA (0, 25, 50, 100 and 150 mg L-1) were applied as foliar application. Leaf area, stem diameter, shoot and root lengths, fresh and dry weights of shoot and root, and physiological parameters were measured. Drought stress (W-2) decreased leaf area by 14.9% compared with normal watering (W-1). High temperature (35 degrees C) increased malondialdehyde (MDA) content by 72.1% compared with control (25.). 35. with W-2 reduced root and shoot dry weights by 71.8% and 51.9% relative to 25 degrees C and W-1. At 35 degrees C, 25 mg L-1 5-ALA increased root length by 17.1% and 3.4% at W-1 and W-2, respectively. 150 mg L-1 5-ALA increased root fresh weight by 101.0% compared with 0 mg L-1 5-ALA at W-1 and 35 degrees C. The highest protein content (8.35 mg g(-1) FW) was achieved at the interaction between W-2, 35 degrees C and 50 mg L-1 5-ALA. At W-2 and 35 degrees C, 150 mg L-1 5-ALA increased proline content by 66.5% relative to 0 mg L-1. The results of the present study suggest that foliar application of 5-ALA could be useful to alleviate the temperature and/or drought stresses of wheat seedling.