Effects of foliage-applied exogenous γ-aminobutyric acid on seedling growth of two rice varieties under salt stress

Abstract

Exogenous γ-aminobutyric acid (GABA) has been used and regarded as a potential enhancer for plant resistance against various biotic or abiotic attackers in the crop production, especially as a promising alleviator against salt stress. In order to determine whether GABA is truly effective in promoting rice resistance under a certain level of salt stress or not and to evaluate its effect on the growth and some physiological responses of two Japonica rice varieties under salt stress. 3-leaf rice seedlings germinated from seeds were cultivated in a separate hydroponic cup with a nutrient solution that was salinized with 0, 25, 50, or 75 mmol K+ of NaCl. A 4 mmol L−1 GABA solution or water were sprayed onto leaves once a day for 8 days prior to an assessment of the seedling growth, the growth indices, root activities and three antioxidant enzyme activities in leaves were measured. Data analyses indicated that as the salt concentration increased, the plant height and the leaf area of both rice varieties decreased, while the dead leaf rate, weight ratio of the dry- and fresh-roots, superoxide dismutase (SOD) and peroxidase (POD) activities increased. Under the same saline conditions, the root activities and the leaf ascorbate peroxidase (APX) activity were enhanced at a low NaCl concentration but reduced when the salt concentration was high. A foliar application of GABA daily on both rice varieties for over a week under 3 different salinized treatments as compared with the corresponding treatments sprayed with water resulted in an enhanced effect on plant height increment by 1.7-32.4%, a reduction of dead leaf rate by 1.6-36.4%, a decline of root dry weight by 9.3-30.9% respectively, and an increment in root activities by 8.1-114.5%, and POD, SOD and APX enzyme activities increased by 5.0-33.3%, 4.1-18.5%, and 7.2-64.4% respectively. However, two rice varieties showed a significant difference in response to various salinized levels. Overall results of this study demonstrate that the application of exogenous GABA on the leaves of rice seedlings under salt stress has improved rice salt tolerance, which should provide a sufficient information for ultimately making it possible to grow rice in salinized soil.

Exogenous γ-Aminobutyric Acid Can Improve Seed Germination and Seedling Growth of Two Cotton Cultivars under Salt Stress

“…Indeed, the K + /Na + ratio was considered a crucial indicator for assessing salt tolerance in cotton [ 3 , 30 ]. In this study, excessive Na + accumulation resulted in the yellowing of cotton seedling leaves ( Figure 2 ), similar to symptoms of salt stress observed in rice [ 31 ]. Salt stress significantly decreased the K + content and K + /Na + ratio, consistent with the findings of Ma‘s study on cotton under the same salt treatment (150 mmol/L NaCl) [ 26 ].…”

Exogenous γ-Aminobutyric Acid (GABA) Enhanced Response to Abiotic Stress in Hypsizygus marmoreus by Improving Mycelial Growth and Antioxidant Capacity

“…Ji et al [25] discovered that GABA accumulation played a crucial role in enhancing Candida glycerinogenes resistance to high osmolarity. A growing number of studies have shown that the exogenous application of low concentrations of GABA increased the levels of endogenous GABA and elicited a variety of biochemical, molecular, and physiological cascades, thereby increasing the tolerance of plants and microorganisms to diverse abiotic stressors [26][27][28]. Chen [29] found that GABA alleviated salt stress during seed germination by increasing Na + /K + transport, promoting dehydration, and regulating the osmotic pressure.…”