Abstract
This study was carried out to appraise whether or not the exogenous application of a potential osmoprotectant, proline, could ameliorate the adverse effects of drought stress on maize seed and seed oil composition, as well as oil antioxidant activity. Water stress reduced the kernel sugar, oil, protein and moisture contents and most of the seed macro- and micro-elements analyzed in both maize cultivars but it increased the contents of seed fiber and ash. Water stress increased the oil oleic acid content with a subsequent decrease in the amount of linoleic acid, resulting in an increased oil oleic/linoleic ratio for both maize cultivars. However, no variation was observed in oil stearic and palmitic acids content due to water stress. A considerable drought induced an increase in seed oil α-, γ-, δ- and total tocopherols and flavonoids were observed in both maize cultivars. However, oil phenolic and carotenoid content as well as 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging activity decreased. Foliar-applied proline significantly increased the content of seed sugar, oil, protein, moisture, fiber and ash in both maize cultivars under well irrigated and water deficit conditions. Furthermore, exogenous application of proline increased the oil oleic and linoleic acid contents. The concentrations of antioxidant compounds namely phenolics, carotenoids, flavonoids and tocopherols estimated in the seed oil increased due to foliar-applied proline under water deficit conditions that was positively correlated with the enhanced oil DPPH free radical scavenging activity. Moreover, the increase in the contents of these antioxidant compounds and oil antioxidant activity due to the foliar application of proline was noted to be more pronounced under water deficit conditions.
Highlights
It is well known that different environmental factors influence the growth and productivity and significantly affect the nutrients profile of oil-seed crops [1]
Grain yield and its quality are governed by a number of factors the duration and rate of grain filling [28] and availability of assimilates, that are negatively influenced under water deficit conditions [1,2,3,6,29]
Exogenous application of proline as foliar spray significantly increased the seed oil, protein, moisture, fiber and ash contents in both the cultivars under water stress and non-stress conditions showing the ameliorating effects of exogenously applied proline on seed proximate composition (Table 1). This enhancement in the seed proximate parameters due to foliar application of proline was more pronounced under water deficit conditions as compared with non-stress conditions
Summary
It is well known that different environmental factors influence the growth and productivity and significantly affect the nutrients profile of oil-seed crops [1]. Exogenous application of proline as foliar spray has been employed to enhance stress tolerance in a number of crops [19,23], very little information is available in the literature on the effects of foliar application of this osmolyte in altering the seed composition, levels of different fatty acids, tocopherols, carotenoids, phenolics and flavonoids in the seed oil of maize. The premier objective of conducting the present study was to assess up to what extent exogenous application of proline could alter seed composition, oil yield, and fatty acids, tocopherols, antioxidants and physico-chemical attributes of the seed oil derived from maize plants grown under water deficit conditions
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