Mechanisms of combined effects of salt and alkaline stresses on seed germination and seedlings of Melilotus officinalis (Fabaceae) in Northeast of China

In line with the salt-alkalinized soils found in the northeast of china,the conditions were simulated to investigate the mechanisms associated with this combination of stresses on melilotus officinalis. the effects of salinity (nacl: 0-300mm) in combination with alkali (ph: 7.1-9.8) on the seed germination and seedlings of m. officinalis were investigated. the results showed that germination was not inhibited completely by the salt-alkali conditions tested. the recovery germinations were significant higher than the control or had no significant differences with the control under the conditions of nacl<200mm and ph=9.0,suggesting that non-germinated seeds may have a strategy to get through and resist the stress during germination stage. for the seedling growth,m. officinalis was capable of surviving at high ph (ph≤9.8) and the salinity (nacl≤200mm) (seedling survival rate: 84.77±8.62%). the characteristic feature for combined salt-alkali stresses is the reciprocal enhancement between salt and alkali stresses. the combined action of salinity and ph should be considered when evaluating the effects of salt-alkali stresses. correlation and regression analyses showed that salinity was the dominant stress factor,while ph was a secondary factor. from the physiological and ecological parameters,we suggested that m. officinalis is a salt-alkali tolerant species which can be used in vegetative restoration of saline soils in the northeast of china. © 2015,pakistan botanical society. all rights reserved.