Salinity is one of the major abiotic stresses which affected on plant growth and reduces plant productivity. Antioxidants compounds considered as one of the methods and strategies to ameliorate the deleterious effects of salinity stress on plants to reduce the effect of oxidative stress. Field experiment was carried out at Sinnuris District which located mainly adjacent to Lake Qarun (saline soil) at El Fayoum Governorate (latitude 29°20 and 29°30 N and longitude 30°43 and 30°56 E) during 2015/2016 and 2016/2017 growing seasons to study the effect of relation between three application methods (seed soaking, foliar spraying and seed soaking plus foliar spraying together) and four concentrations (without treatment, tap water, 100 ppm and 200 ppm of ascorbic acid) of ascorbic acid on some biochemical and physiological characteristics, antioxidant enzyme activity as well as growth, yield and quality of sugar beet (Beta vulgaris var. saccharifera, L.) under salt stress conditions. The treatments were arranged in a strip-split plot design with three replications. The vertical plots were occupied with three application methods while, the horizontal plots were devoted to four ascorbic acid treatments.
Results showed that application of soaking sugar beet seed in ascorbic acid (AsA) plus foliar spraying at 50 and 70 days from sowing significantly increased chlorophyll a, b and carotenoides, LAI, catalase (CAT) and superoxide dismutase (SOD) activities , yield components and sucrose % in both seasons while juice impurities (K, Na and α -Amino -N) were decreased and significantly increased root yield by (9.19, 9.63%) and sugar yield by (13.43, 15.59%) compared to AsA applied as a seed soaking or foliar spray in the 1st season and the same trend was attained in the 2nd season.
Applying 200 ppm of ascorbic acid was more effective and significantly increased root and sugar yields and sucrose % and caused more reduction in juice impurities in comparison to the control, in both seasons.
Higher stomata area, lower stomata density and stomata closure% were recorded by seed soaking plus foliar spraying with 200 ppm AsA treatment for upper and lower surface of sugar beet leaf. Applying seed soaking plus foliar spraying by 200 ppm of ascorbic acid significantly increased root yield by (6.99 and 4.54 ton/fed) and sugar yield by (2.19 and 2.06 ton/fed) over that gained by untreated plants in the 1st and 2nd seasons.