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MECHANISMS OF COMBINED EFFECTS OF SALT AND ALKALINE STRESSES ON SEED GERMINATION AND SEEDLINGS OF MELILOTUS OFFICINALIS (FABACEAE) IN NORTHEAST OF CHINA

THI SOAN VU^1†, DAWEI ZHANG^1†, WEIHUA XIAO², CHUNYU CHI¹, YI XING¹, DONGDONG FU¹ AND ZENING YUAN^1*

Abstract: 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.

Key words: Melilotus officinalis, Salt-alkali stress, Germination, Seedling growth, Salt-alkali tolerance.

¹Key Laboratory of Molecular and Cytogenetics, Heilongjiang Province; College of life Sciences and Technology, Harbin Normal University, Harbin 150025, China

²Tianjin Tanggu No.1 Moddle school, Tianjin, 300450, China

^*Corresponding author’s e-mail: xiaoyuan168ok@163.com

^†These authors contributed equally to this paper.