Abstract
Numerous studies have demonstrated the potential of sugar beet to lose the final sugar yield under water limiting regime. Ample evidences have revealed the important role of mineral nutrition in increasing plant tolerance to abiotic stresses. Despite the vital role of calcium (Ca2+) in plant growth and development, as well as in stress responses as an intracellular messenger, its role in alleviating drought stress in sugar beet has been rarely addressed. Here, an attempt was undertaken to investigate whether, and to what extent, foliar application of Ca2+ confers drought stress tolerance in sugar beet plants exposed to drought stress. To achieve this goal, sugar beet plants, which were grown in a high throughput phenotyping platform, were sprayed with Ca2+ and submitted to drought stress. The results showed that foliar application of Ca2+ increased the level of magnesium and silicon in the leaves, promoted plant growth, height, and leaf coverage area as well as chlorophyll level. Ca2+, in turn, increased the carbohydrate levels in leaves under drought condition and regulated transcriptionally the genes involved in sucrose transport (BvSUC3 and BvTST3). Subsequently, Ca2+ enhanced the root biomass and simultaneously led to induction of root (BvSUC3 and BvTST1) sucrose transporters which eventually supported the loading of more sucrose into beetroot under drought stress. Metabolite analysis revealed that the beneficial effect of Ca2+ in tolerance to drought induced-oxidative stress is most likely mediated by higher glutathione pools, increased levels of free polyamine putrescine (Put), and lower levels of amino acid gamma-aminobutyric acid (GABA). Taken together, this work demonstrates that foliar application of Ca2+ is a promising fertilization strategy to improve mineral nutrition efficiency, sugar metabolism, redox state, and thus, drought stress tolerance.
Highlights
Sugar beet (Beta vulgaris L.) is an industrial crop which belongs to the Chenopodiaceae family [1]
The impact of water stress was evaluated through a set of parameters related to growth, measured on beetroot and leaves at 35 days after first Ca2+ application (DAA)
Drought stress did not provoke a particular change in beetroot dry weight (DW) as well as beetroot diameter compared to the control plants (Figure 1A,B)
Summary
Sugar beet (Beta vulgaris L.) is an industrial crop which belongs to the Chenopodiaceae family [1]. The first consequence of drought is stomatal closure which can reduce water potential resulting in an inhibition of carbon dioxide uptake, photosynthesis, and subsequent reduction in carbohydrate production and its allocation to the root organ [7]. Another early consequence of low water availability under drought is a decrease in total nutrient uptake and translocation to shoots [8]. This results mainly from a reduced transpirational flow and a decreased mass flow to the root surface of soil water containing soluble nutrients like potassium (K), nitrogen (N), and Ca2+ [9]. It is crucial to maintain the proper uptake of mineral nutrition and functioning of photosynthetic machinery in order to prevent the losses of sugar yield under such a harsh condition
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