Silicon improves salt tolerance by increasing root water uptake in Cucumis sativus L.

Abstract

Silicon enhances root water uptake in salt-stressed cucumber plants through up-regulating aquaporin gene expression. Osmotic adjustment is a genotype-dependent mechanism for silicon-enhanced water uptake in plants. Silicon can alleviate salt stress in plants. However, the mechanism is still not fully understood, and the possible role of silicon in alleviating salt-induced osmotic stress and the underlying mechanism still remain to be investigated. In this study, the effects of silicon (0.3 mM) on Na accumulation, water uptake, and transport were investigated in two cucumber (Cucumis sativus L.) cultivars ('JinYou 1' and 'JinChun 5') under salt stress (75 mM NaCl). Salt stress inhibited the plant growth and photosynthesis and decreased leaf transpiration and water content, while added silicon ameliorated these negative effects. Silicon addition only slightly decreased the shoot Na levels per dry weight in 'JinYou 1' but not in 'JinChun 5' after 10 days of stress. Silicon addition reduced stress-induced decreases in root hydraulic conductivity and/or leaf-specific conductivity. Expressions of main plasma membrane aquaporin genes in roots were increased by added silicon, and the involvement of aquaporins in water uptake was supported by application of aquaporin inhibitor and restorative. Besides, silicon application decreased the root xylem osmotic potential and increased root soluble sugar levels in 'JinYou 1.' Our results suggest that silicon can improve salt tolerance of cucumber plants through enhancing root water uptake, and silicon-mediated up-regulation of aquaporin gene expression may in part contribute to the increase in water uptake. In addition, osmotic adjustment may be a genotype-dependent mechanism for silicon-enhanced water uptake in plants.

Silicon and the Association with an Arbuscular-Mycorrhizal Fungus (Rhizophagus clarus) Mitigate the Adverse Effects of Drought Stress on Strawberry

“…In contrast to the leaves, the root concentration of organic osmolytes increased by AMF and Si treatments, suggesting a different strategy for the adjustment of the water economy triggered by AMF and Si in the roots than in the leaves of strawberry. In tomatos, water stress did not change the root osmotic potential in Si-treated plants [46], and in cucumbers, the role of the osmotic driving force in the Si-mediated enhancement of water uptake was genotype-dependent [47]. Collectively, these results suggest different strategies for the improvement of water content and uptake capacity under osmotic stress in Si-treated plants depending on plant organ, species, and genotypes.…”

The Interactions of Aquaporins and Mineral Nutrients in Higher Plants

“…Si is beneficial to the mechanical and physiological properties of plants and helps plants to overcome biotic and abiotic stress [34,119,120,121]. Under salt stress, Si can improve plant tolerance through enhancing root water uptake which contributes to the regulation of aquaporin activity and gene expression [122,123]. The Si uptake by plants in soil solution is through silicic acid [Si(OH) 4 ], an uncharged molecule [34].…”

Isolation and functional characterization of CsLsi1, a silicon transporter gene in Cucumis sativus

“…Silicon is the second most abundant element on earth (Epstein ). It can exert beneficial effects on the growth of plants, especially when they are subjected to various biotic and abiotic stresses such as drought (Shi et al ), salinity (Zhu et al ), heat (Soundararajan et al ), cold (Azeem et al ), metal toxicity (Kim et al , Wu et al ), lodging (Ma ), nutrient imbalance (Hernandez‐Apaolaza ), plant pathogens (Gao et al ) and insect pests (Liang et al ). These benefits have been attributed to silicon accumulation in plants, and the beneficial effects are usually more obvious with higher silicon accumulation (Ma ).…”