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THE PHYSIOLOGICAL VARIATIONS OF ADAPTATION MECHANIAM IN GLYCINE SOJA SEEDLINGS UNDER SALINE AND ALKALINE STRESSES

SHUAI SHAO1, MINGXIA LI1, DONGSHUANG YANG AND JING ZHANG ANG LIANXUAN SHI*

School of life sciences, Northeast Normal University, Changchun 130024, China

*Corresponding author email: lianxuanshi@nenu.edu.cn; Fax: 086-431-85695065

1These authors contributed equally to this work

Abstract

The seedlings of Glycine soja were treated with varying saline stress and alkaline stress. The growth, photosynthesis and concentrations of inorganic ions in tissue sap of stressed seedlings were measured to elucidate the mechanism of saline and alkaline stress (high pH) damage to G. soja, and the differences between physiological adaptive mechanism to alkaline stress and saline stress. Our experimental data showed alkalinity had a more severe effects on G. soja seedlings than salinity in the similar concentration, severely inhibited shoot and root growth, and photosynthesis. Diurnal change of pN showed the bimodal curves getting less obvious and transformed to be single peak with increasing stress intensity which might be an efficient energy-conserving strategy for G. soja to adapt to saline and alkaline stress. Na+/K+ were all increased, with greater degrees of increasing under alkaline than under saline stress, cations and anions were almost not accumulated under high alkaline stress, while the influx of superfluous Na+ can be balanced by the accumulation of Cl-, SO42-, H2PO4- in root under saline stress. This indicated that the roots of G. soja were injured so severely that couldn’t absorb Na+ and keep ion balance under high alkaline stress including high-pH stress, which might lead to greater accumulation of Na+ in leaves under alkaline stress than that under saline stress, and then sharply reduced the growth and photosynthesis. pN of G. soja seedlings was promoted under low concentration saline and alkaline stresses. Na+/K+ were significant lower in leaves compare with that in roots, and a large amount of Na+ was accumulated in stems of G. soja seedlings under both stresses. Under alkaline stress, the K+, NO3-, Mg2+ and Ca2+ contents in leaves were increased with increasing Na+, and maintain high water content in root. Our results showed obvious differences between physiological adaptive mechanisms to saline stress and alkaline stress. This study would provide a theoretical basis for protection, screening and utilization of wild soybean and breeding new varieties of cultivated soybean.

Key words: Glycine soja, Growth, Photosynthesis, Ion homeostasis, Saline stress, Alkaline stress.

Abbreviations: AS - alkaline stress; Car - carotenoid; Chl - Chlorophyll; Chl a - Chlorophyll a; Chl a/b - Chlorophyll a/b; Chl b - Chlorophyll b; CK - Control; DM - dry mass; E - transpiration rate; FM - fresh mass; gs - stomatal conductance; pN - net photosynthetic rate; RGR - the relative growth rate; SS - Saline stress; WC - The water content; WUE - water use efficiency.