Plant growth promoting rhizobacteria in combination with plant growth regulators attenuate the effect of drought stress

摘要

The present study evaluates the effects of plant growth hormones (PGR), salicylic acid (SA), abscisic acid (ABA) and plant growth promoting rhizobacteria (PGPRs) Rhizobium pisi (DSM 30132 strain) applied alone and in combination, on pea ( Pisum sativum L.) cv. Florida plants under well-watered and drought stressed conditions. Prior to sowing seeds were soaked for 5h in broth culture (10 8 cfu/ml) of Rhizobium pisi and SA /ABA. Seeds were soaked for 6h in distilled water, ABA, SA solutions. Plants were subjected to drought stress on 21 days old seedlings by withholding the supply of water at two different time points; for 4d (TP 1 ) and for 8d (TP 2 ). Rhizosphere soil of abscisic acid treated plants exhibited higher retention of soil moisture at TP 1 . Abscisic acid decreased the fresh and dry weight of plants under unstressed condition but increased the fresh weight as well as relative water content under drought stress. The response of Rhizobium and SA were at par. Rhizobium and SA ameliorated the adverse effects of drought stress more effectively than ABA. The Rhizobium inoculation reduced the stomatal conductance under unstressed condition but significantly increased stomatal conductance under drought stress at TP 2 . SA alone and in combination with Rhizobium stimulated the stomatal conductance under unstressed condition. Under drought stress, at TP 1 all the treatments alone and in combination increased the relative water content (RWC) significantly over drought stressed plants. The FV/FM ratio was increased in SA treatment or in combination with SA, Rhizobium and ABA.