Foliar supplements improve physio-biochemical responses and root Brix in sugar beet under water deficit condition

Abstract

Sugar beet is a major sugar crop, it is a moderate drought tolerant plant however, high dehydration levels or prolonged drought exposure durations can affect its growth and physiology. Two seasons of study were conducted in a split plot design during winter-summer under Odisha conditions, to evaluate the effect of foliar supplements (nano silicon 1 mM, humic acid 300 ppm, jasmonic acid 5 µM, salicylic acid 100 ppm, boric acid 1000 ppm, kaolin 5 % and  chitosan 200 ppm) in tropical sugar beet LS-6 variety, growing under 3 irrigation intervals as 3 days (Normal watering -NW), 7 days (S1) and 14 days (S2) of water withholding on its physio-biochemical changes and the root Brix. The effect of water deficit stress on physiological processes was observed with the decline of relative water content (RWC %) and the membrane stability index (MSI %) up to 25.33 % and 23.38 % respectively, after 4 cycles of severe stress (S2). In response to water scarcity, leaf chlorophyll and protein content decreased, while proline, sugars and ascorbic acid content in the leaves increased. Similarly, root Brix increased with the severity of stress. The application of various foliar treatments regulated the physiological processes by stabilising the water balance in the stressed leaves and strengthening the cell membrane. Moreover, these treatments protected the chlorophyll and protein content by inhibiting their destruction under stress condition and boosted the accumulation of proline, total soluble carbohydrate and ascorbic acid amount in the leaves. Humic acid was recorded as the most effective foliar treatment in case of chlorophyll retention. Nano silicon proved as efficient protective supplement for membrane stability and water content. Salicylic acid also induced more accumulation of ascorbic acid in the leaves with an increment of 41.79 % under S2 after 4th spray. In contrast, boron was the most effective treatment to maintain root Brix with 10.52 % increment against stress control when subjected to severe stress (S2) of 2 months.