Agricultural productivity is subjected to enormous environmental constraints, particularly to salinity and drought due to their higher magnitude of adverse impacts and worldwide distribution. Silicon (Si) was found to play a favorable role in salinity and drought stress alleviation of soybean cultivar Daewonkong. All growth attributes insignificantly improved with Si nutrition. The endogenous bioactive GA1 and GA4 content increased with the application of elevated Si level both under normal and stressful condition. JA contents sharply increased with NaCl and PEG application but decreses with Si added to salt and drought stress treatments. SA level increased with NaCl and PEG and was further enhanced with Si in the salt treated plants, but reduced with the combined application of Si and PEG. The endogenous bioactive GA1 and GA4, JA and ABA content of soybean leaves were analyzed through chromatograph/mass spectrometer (GC/MS) in selected ion monitoring (SIM) mode, while SA content was quantified with HPLC.

The adverse effects of salinity and drought on soybean cultivar Hwangkeumkong were also investigated. Endogenous bioactive gibberellins GA1 and GA4, jasmonic acid (JA), abscisic acid (ABA) and salicylic acid (SA) content and pertinent changes in response to basic and double NaCl (70 mM & 140 mM) and PEG (8% & 16%) were examined. We found that plant growth and yield components significantly reduced with the application of NaCl and PEG during pre-flowering and post-flowering growth periods. The endogenous bioactive GA1 and GA4content decreased under elevated salt and drought stress. However, an insignificant increase in GA4level was noted with 8% PEG, applied during post-flowering growth stage. JA levels significantly increased with NaCl and PEG applications, but declined with elevated PEG applied during post-flowering period. SA level drastically reduced with NaCl, while insignificantly reduced with PEG. Endogenous ABA contents of leaves increased with elevated NaCl and PEG application. The endogenous bioactive GA1 and GA4, JA and ABA content of soybean leaves were analyzed through chromatograph/ mass spectrometer (GC/MS) in selected ion monitoring (SIM) mode, while SAcontent was quantified with HPLC.