Effects of endogenous abscisic acid, jasmonic acid, polyamines, and polyamine oxidase activity in tomato seedlings under drought stress

• ABA, JA, free PAs, and PAO in roots and leaves were higher than controls under drought.
• A significantly positive correlation existed between the PAs and PAO activity.
• The ABA and JA content exhibited an extremely close correlation with PAs.

Drought stress causes various physiologic and biochemical effects in plants. The phytohormones in plant systems are closely involved in responses against drought stress. However, information on the regulatory effect of abscisic acid (ABA), and free polyamine (PA) metabolism on the accumulation of JA is limited. Elucidating the endogenous mechanisms that confer stress resistance is essential to providing insights into the potential of plants to adapt to environmental change. This study aims to determine the relationship between the concentrations of abscisic acid (ABA) and jasmonic acid (JA) and the accumulation of free PAs (putrescine, spermine, and spermidine), as well as with polyamine oxidase (PAO) activity, in tomato (Lycopersicon esculentum M.) seedlings grown hydroponically under polyethylene glycol – induced drought stress. The results indicate that the concentrations of endogenous ABA, JA, and free polyamines, and the PAO activity in the roots and leaves of tomato seedlings were generally higher in the treatment groups than in the untreated controls. A significantly positive correlation was observed between the concentrations of endogenous polyamines and PAO activity (R = 0.708**) in roots and leaves of tomato seedlings. The time course in the present experiment demonstrated that the ABA concentrations increase in the roots prior to that in the leaves. Therefore, under drought stress, the higher concentrations of endogenous spermine and spermidine in the roots and leaves stimulate the simultaneous accumulation of endogenous ABA and JA with increasing PAO activity.