*2.3. E*ff*ects of GABA Priming on the Sugar, Protein, Starch and GABA Contents under Salinity, Osmotic Stress and OS*+*S*

The mean data concerning effects of salinity and osmotic stress and their combination on the sugars, protein, and starch contents are presented in Table 3. The results reported that osmotic stress, salinity and their combination decreased the sugar content by 49.60%, 60.32%, 66.64%; protein content by 54.85%, 57.16% and 64.51; and starch content by 49.90%, 59.12%, and 56.54%, respectively, as compared with the unstressed condition. However, priming with GABA improved the sugar content under osmotic stress, salinity and OS+S by 36.36%, 44.88% and 59.07%; protein content by 32.28%, 52.26% and 49.56% and starch content by 47.96%, 44.42% and 26.93%, respectively, as compared with unprimed seeds. The osmotic stress, salinity and OS+S resulted in a significant increase in the GABA content as compared with the unstressed condition (Table 3). Priming seeds with GABA significantly improved the GABA content under salinity and osmotic stress and their combination, and the highest GABA content was recorded under osmotic stress as compared with either salinity alone or OS+S stress. The current study emphasized that application of 0.5 mM GABA resulted in the accumulation of sugars, starch and protein (Table 3), which may serve as osmolytes to provide energy and carbon at times when photosynthesis may be inhibited under salinity and osmotic stresses.



Values are means ± SD (*<sup>n</sup>* = 3) and the same letters within a column indicate no significant difference at a 95% probability level (*<sup>p</sup>* < 0.05). **Table 2.** Effects of GABA treatment on the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intracellular CO2 concentration (Ci);chlorophyll content (SPAD), water potential (WP, Ψw), osmotic potential (OP, Ψs), relative water content (RWC) and water use e fficiency (WUE) of rice seedlingsexposed to salinity, osmotic stress and their combined stress.



**Table 3.** Effects of GABA treatment on the GABA content (mg/g DW), sugars (μg/g FW), protein (mg/g FW), starch (%); proline (μg/g FW); hydrogen peroxide (H2O2,g−1min−1g−1g−1mg−1

Values are means ± SD (*<sup>n</sup>* = 3) and the same letters within a column indicate no significant difference at a 95% probability level (*<sup>p</sup>* <

0.05).
