Abstract
The influence of seed priming with varying levels (50 and 100 mg L−1) of alpha-tocopherol (Toc) was investigated in carrot plants under water-deficit conditions. For this purpose, two cultivars of carrot, DC4 and DC90, were selected and subjected to well-watered (100% field capacity (FC)) and water-deficit stress (50% FC). After 21 days of water-deficit conditions, a significant suppression was observed in shoot and root fresh and dry weights, their lengths, chlorophyll a, b and total contents, and total soluble proteins (TSP). However, an up-regulatory effect of water stress was observed on the concentrations of glycinebetaine (GB), hydrogen peroxide (H2O2), malondialdehyde (MDA), ascorbic acid (AsA), total phenolics as well as the activities of catalase (CAT) and peroxidase (POD) enzymes. Exogenous application of alpha-tocopherol was effective in reducing the accumulation of H2O2 and MDA contents and improving all growth attributes, contents of chlorophyll, proline, GB, AsA, total phenolics, TSP, and the activities of CAT and POD enzymes. Of both carrot cultivars, cv. DC4 had better performance in terms of growth attributes, whereas the response of the two cultivars was similar in all other attributes varying water regimes. Overall, it is suggested that seed priming with 100 mg L−1 Toc was effective in improving plant growth attributes, osmoprotectants and the oxidative defense system of carrot plants under water-deficit conditions.
Highlights
Seed priming with Toc considerably (p ≤ 0.001; 0.01) improved all the growth attributes of carrot plants subjected to both water regimes
DC4 had better performance in terms of shoot and root fresh weights, as well as root length under both water regimes. The response of both carrot cultivars to water stress and exogenously applied Toc was similar for other growth attributes
We found that non-enzymatic antioxidants increased significantly under drought stress conditions in both carrot cultivars
Summary
A significant decrease in growth and yield production of many crops was noticed that is believed to be associated with reduced transpiration rate, chlorophyll pigments, photosynthetic rate, water potential, and gaseous exchange characteristics [2,3] Morphological adaptations such as trichome/bark thickness and leaf wax can effectively suppress water loss, thereby providing protection to plants against water shortage conditions [4]. ROS of various forms like superoxide, hydroxyl radicals, hydrogen peroxide and singlet oxygen are generated in several parts of the cell such as microbodies, chloroplasts and mitochondria [14,15] Another vital response of plants to drought stress is cell osmoregulation, which is mediated by the accumulation of solutes such as proline, sugars and glycinebetaine, and these biomolecules are believed to protect cellular structures and conserve cellular water content [5,16]. By accumulating osmoprotectant compounds such as proline, trehalose and polyamines, plants can resist a stress [17,18]
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