Rhizobium Symbiosis Leads to Increased Drought Tolerance in Chinese Milk Vetch (Astragalus sinicus L.)

Chinese milk vetch (Astragalus sinicus L.) is an important leguminous green manure that frequently suffers from seasonal drought. To improve its drought tolerance, the effects of rhizobia inoculation on tolerance and underlying physiological mechanism were investigated. Drought in combination with nitrogen assimilation, free amino acids, polyamines was investigated active nodules (AN), inactive (LN), or without (NN). AN plants had increased compared to LN NN plants. Glutamine synthetase (GS), glutamine 2-oxoglutarate transferase (GOGAT), glutamate dehydrogenase (GDH) activities decreased after drought, higher levels than under both control stress conditions. Higher proline (Pro), arginine (Ala), alanine (Glu) observed Putrescine (Put), spermidine (Spd), spermine (Spm) response Put Spd maintained It suggested nodulation leads vetch, which associated improved fixation ammonium turn lead promotion amino-acid polyamine synthesis.