Abstract: Using Colombia wild Arabidopsis thaliana (WT), phospholipase Dδ (PLDδ) deletion mutant (pldδ) and 9-lipoxygenase (9-LOX) deletion mutants lox1 and lox5 seedlings as materials, we examined the effects of PLDδ and 9-LOX on biosynthesis of jasmonic acid (JA) and seed germination ofA. thalianaunder drought stress (0.3 mol·L^-1 mannitol). The results showed that drought stress markedly increased the activities of PLD and LOX and the gene expressions of PLDδ and LOX1. Under drought stress, the LOX activity and JA content in pldδ seedlings were significantly lower than those in WT. Both LOX and JA significantly increased after phosphatidic acid (PA) addition and were higher than those in WT. Drought stress significantly inhibited seed germination of pldδ, lox1 andlox5 mutants, with the strongest inhibitory effect on lox1. Under drought stress, the enhancement of PLD activity was related to PLDδ expression while the increasing activity of LOX was related to LOX1 andLOX5 expressions, with the dominant role from LOX1. PLDδ/PA was located at the upstream of 9-LOX and involved in the JA synthesis. All PLDδ, LOX1 and LOX5 participated in seed germination of A. thaliana under drought stress, with a dominant role of LOX1 in this process. Both PLDδ and 9-LOX were involved in PA and JAmediated seed germination.

Key words: nitrogen cycling, soil, grazing