Polyamines protect mung bean [Vigna radiata (L.) Wilczek] plants against drought stress

Introduction: Drought is a major environmental factor that limits crops productivity. To cope with the adverse effects of drought, plants have evolved various adaptive mechanisms, such as accumulation of osmolytes. Polyamines (PAs) play an important role in the plant growth and development and response to abiotic stresses. This experiment was conducted to investigate the role of exogenous PAs on drought tolerance of mung bean. Methods: Mung bean seeds were soaked in 0 or 100 mu M putrescine (Put), spermidine (Spd), spermine (Spm), or their mixture for 10 hr. Then, treated seeds were sown in the field and were exposed to drought stress condition. Results: The growth attributes including shoot length, biomass, leaf area index (LAI), and grain yield markedly reduced due to drought stress. Drought stress also decreased soluble protein content, relative water content (RWC), chlorophyll value, stomatal conductance (g(s)), and net photosynthetic rate (P-N) but increased malondialdehyde (MDA), total soluble sugars (TSS), and proline contents. Nonetheless, seed priming with the mixture of PAs alleviated adverse effects of drought stress and improved all growth attributes. Exogenous application of PAs also increased soluble protein content, RWC, chlorophyll value, P-N, and more increased TSS and proline contents but decreased g(s) and MDA level. Discussion: These results indicated that seed treatment with PAs especially combined treatment of Put + Spd + Spm could enhance drought tolerance of mung bean plants through the accumulation of osmoprotectants, improving water status, chlorophyll value, and P-N as well as reduction of oxidative damage.