Interaction of vesicular arbuscular mycorrhizae, hormones and drought in soybeans

Vesicular Arbuscular Mycorrhizae (VAM) has been known to help plants in different types of environmental situations. The purpose of this study was to determine growth and yield response of drought stressed soybean Glycine max to two different species of vesicular abuscular mycorrhizae (Glomus intraradiesces and Glomus fasciculatum) in interaction with exogenous hormonal application and to compare the levels of endogenous ABA in VAM and non-VAM droughted plants. Two separate experiments were performed in 2 x 2 x 3 full factorial design for study of each VAM species. In the greenhouse plants were with foliar application of 10−6 M ABA or IBA solutions one week before exposure of drought stress. In third set of experiments designed as 2 x 2 factorial with VAM and drought as the main factors, endogenous levels of ABA of the VAM and non-VAM plants were estimated by ELISA under droughted and non-droughted conditions. Plants phosphorus content was also determined to study the relationship between ABA levels of the plants and phosphorus content. Both species of VAM increased vegetative growth as well as grain yield, as compared to non-VAM plants under drought stress. Measurements showed that the VAM infected plants had higher phosphorus content (Mean = 2.443 mgs/gm of plant shoot) than non-VAM drought stressed plants (0.787 mgs/gm of plant shoot). VAM infected plants had lower level of ABA (mean = 0.342 picomoles/gm of the fresh weight of shoot) as compared to no-VAM plants (mean = 0.429 picomoles/gm of the fresh weight of shoot). The highest levels of ABA were found in drought stressed non-VAM plants and the lowest in VAM, non-droughted plants. Total seed weight of the VAM plants was in direct correlation with the phosphorus content. The comparison of the both species of VAM used in the study showed that Glomus fasciculatum had significantly better influence on the drought stressed soybeans than Glomus intraradieces.