Seeds primed with 5-aminolevulinic acid mitigated temperature and drought stresses of wheat at germination and early seedling growth

Drought and temperature stresses are known as primary factors limiting germination and seedling growth. Seed priming with plant growth regulators is one of the popular approaches to minimize adverse environmental stresses. This study was carried out to examine the role of seed priming with 5-aminolevulinic acid (5-ALA) at different levels (0, 25, 50, and 100 mg L-1) in germination and seedling growth of three wheat (Triticum aestivum L.) 'Emam', 'Gomria', and 'Zakia' under high temperature and drought stresses using a range of temperatures (25, 30, and 35 degrees C) and water potentials (0.0 and -0.5 MPa). Water uptake, germination and early seedling growth attributes were measured. Drought stress and high temperature decreased germination%, germination index, and shoot fresh weight by 39.2%, 35.4%, and 48.6%, respectively, as compared with 0.0 MPa and 25 degrees C. Seeds of 'Zakia' primed with 50 mg L-1 5-ALA at -0.5 MPa, and 35 degrees C increased fresh and dry weights of the root by 19.8% and 68.4% relative to 0 mg L-1. For interaction between variety and 5-ALA, the highest germination% (90.3%) was recorded in 'Emam' with 50 mg L-1 5-ALA. Treatment 100 mg L-1 5-ALA decreased mean germination time by 24.5% and 28.9% at 25 and 35 degrees C, respectively; 50 mg L-1 5-ALA increased seedling vigor index by 16.3% as compared with 0.0 mg L-1 at -0.5 MPa and 35 degrees C. The 5-ALA enhanced water imbibition of the three varieties under drought and temperature stresses. This study suggested that seed priming with 5-ALA is a possible way to mitigate the negative effects produced by drought and temperature stresses on germination and early seedling growth of wheat.