Abstract
Salinity is an important restrictive factor for plant growth and ecosystem productivity. However, the endogenous mechanisms by which salinity constrains plant growth are not well understood. To determine the mechanism by which soil salinity suppresses plant growth under salt stress, the effect of soil salinity on hormones in the leaves of Leymus chinensis and the plant density, height and biomass were examined in Songnen meadow steppe. The plants with rhizosphere soil were collected in the growing season (May, June, July, September, October) from the field at different salt levels. The shoot density, height and biomass accumulation of L. chinensis highly decreased with the increase in the soil salinity. Salinity significantly reduced the synthesis of the hormones gibberellic acid (GA3) and indoleacetic acid (IAA), but it increased the concentration of abscisic acid (ABA). Significant negative correlations between the soil electrical conductivity and plant leaf hormones (GA3, r = -0.853, P < 0.05; IAA r = -0.971; P<0.01) related to plant growth and positive correlation with ABA (r = 0.931, P<0.01) were observed. Significant positive correlations between the plant hormones related to plant growth (GA3 and IAA) were observed, but negative correlations were found between ABA and plant density (r = -0.872, P<0.05) and height (r = -0.833, P<0.05). The results suggest that soil salinity might restrict plant growth and biomass accumulation by reducing the synthesis of GA3 and IAA and increasing the synthesis of ABA under salt stress.
Highlights
Salinity is one of most important factors that restricts agriculture and livestock husbandry
We found that the concentration of GA3 and indoleacetic acid (IAA) significantly decreased with increases in soil salinity, which might suggest that soil salinity can inhibit the synthesis of plant hormones
Our results found that the soil salinity highly reduced the plant shoot density, height and aboveground biomass of L. chinensis in the saline-alkali Songnen meadow ecosystem, which will restrict the development of animal husbandry
Summary
Salinity is one of most important factors that restricts agriculture and livestock husbandry. The poor soil conditions caused by salinity can hinder plant seed germination (Song et al, 2005; Zhang et al, 2010), seedling survival and growth (Song et al, 2009). Numerous previous studies have demonstrated the mechanisms by which salinity affects plant growth using the three main approaches of osmotic effect, toxic effect, and nutritional stress (English and Colmer, 2013; Nublat et al, 2001; Song et al, 2006). It is well known that changes in the concentrations of the endogenous hormones can affect plant growth (Nimir et al, 2014). The effects of soil salinity on plant endogenous hormones and the endogenous mechanisms by which salinity suppresses the growth of plants are still not well understood
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