The effects of glycine betaine on some morphological and physiological characteristics of Salsola imbricata L. under salinity stress.

After drought, salinity is the second most common environmental limiting factor for agricultural production. Salsola imbricata L. from Chenopodiaceae is a small shrub plant. Glycine betaine is one of the most commonly compatible solutes and is the most abundant compound among the many known quaternary ammonium compounds in response to stress. This study was conducted to evaluate and compare the some growth and enzymatic properties of Salsola imbricata L. using glycine betaine in response to the different salt stress levels.

This study was conducted as factorial based on a completely randomized design with 3 replications at Research Greenhouse of National Salinity Research Center during 2017-18 growing season. The treatments were four levels of salinity: 3 (control), 10, 30 and 60 dS M-1 (saline water resource) and two levels of GB consisted of without application and spraying with 50 mM concertation.Throughout the experiment, steam length, root length, root-shoot length ratio, shoot dry weight, root dry weight, root volume, chlorophyll content, soluble sugars, proline and protein were evaluated.

The results indicated that increasing in salinity levels significantly decreased stem length in both with and without glycine betaine (GB) treatments.The highest and lowest stem length was obtained in 3 dS m-1 using GB and 60 dS m-1 without GB application, respectively. Regarding root length, increasing salinity levels from 3 to 60 dS m-1 caused a significant decrease in root length. The use of GB did not cause a significant difference in root length than no GB except in 3 dS m-1 treatments. The results showed that treated GB plants had a lower root to shoot length ratio, so that the GB application reduced root to shoot length ratio by 19.23%. Increasing levels of salinity significantly reduced shoot dry weight, so that with increasing salinity from 3 to 60 dS m-1, a 40.8% reduction was observed in shoot dry weight. The results indicated a significant effect of GB application on increasing shoot dry weight, as GB increased the shoot dry weight by 4.46 g plant-1. Increasing salinity levels up to 30 dS m-1 did not affect the amount of soluble sugar, however increasing salinity level to 60 dS m-1 resulted in significant increasing 31.97% soluble sugar by 31.97% compared to 3 dS m-1. The results revealed that proline content was decreased when GB was applied than no-GB treatments at all salt stress levels, however this reduction was only significant at 30 and 60 dS m-1 salinity levels.

Increasing salt stress from 3 to 60 dS m-1 significantly reduced stem and root length, root to shoot length ratio, shoot and root weight, and root volume. Application of GB increased stem and root length, shoot and root dry weight and root volume. Increasing salinity levels enhanced soluble sugar and proline content. The amount of proline in GB application treatment was higher than no-GB at all salinity levels. It seems that in this study the use of GB increased plant ability against salt stress by improving the plant growth characteristics.