Improving fatty acid composition of soybean yield under NaCl stress by soaking seeds in ascorbate

The present study aimed to improve the fatty acid composition of soybean seeds (Giza 82) grown under salinity using ascorbate (AsA). To achieve this purpose, two homogenous sets of seeds were soaked either in water or in 0.5 mM AsA and then grown in plastic pots and irrigated with Long Ashton for 18 days, after which NaCl at 0, 100, and 200 mM was added to Long Ashton solution for a month. The second leaves of some samples were harvested for the various analyses while the other samples were left for seed production. The results indicated that NaCl led to a significant decrease in the level of K+ in the leaves and in the ratio of K+/Na+ as well as pigments, protein, phenolics, and endogenous AsA, while it led to inhibition of the activity of catalase (CAT), ascorbate peroxidase (APX), and the quantity of Rubisco. By contrast, there were increases in Na+, H2O2, malondialdehyde (MDA), and soluble sugars. Moreover, the total saturated fatty acids of the crop seeds increased but both the unsaturated (omega-3, 6, 7, and 9) and total fatty acids decreased. The effects of NaCl on the varied parameters were concentration dependent. Soaking the seeds in AsA resulted in a rise in K+, K+/Na+ ratio, pigments, protein, phenolics, and endogenous AsA contents coincided with enhancements in CAT and APX activities and Rubisco quantity while the accumulated Na+, H2O2, MDA and soluble sugars decreased. This attenuation was obvious for 100 mM NaCl treated samples when AsA is given; however, at high salinity stress, AsA treatment seemed less effective. Under these circumstances, AsA attenuated the induced decreases in both total and omega fatty acids but reduced the accumulation of saturated fatty acids resulting in an improvement in oil quality. These results support the role of AsA in improving K+/Na+ ratio, Rubisco, and the antioxidant system for the subsequent improvement in fatty acid composition of the crop.