RESUMO
KEY MESSAGE: 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.
Assuntos
Cucumis sativus/fisiologia , Raízes de Plantas/metabolismo , Tolerância ao Sal/efeitos dos fármacos , Silício/farmacologia , Água/metabolismo , Aquaporinas/genética , Aquaporinas/metabolismo , Transporte Biológico , Biomassa , Carboidratos/análise , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/genética , Cucumis sativus/crescimento & desenvolvimento , Ditiotreitol/farmacologia , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Genes de Plantas , Cloreto de Mercúrio/farmacologia , Osmose/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Estômatos de Plantas/efeitos dos fármacos , Estômatos de Plantas/fisiologia , Transpiração Vegetal/efeitos dos fármacos , Característica Quantitativa Herdável , Tolerância ao Sal/genética , Plântula/efeitos dos fármacos , Plântula/fisiologia , Sódio/metabolismo , Solubilidade , Xilema/efeitos dos fármacos , Xilema/fisiologiaRESUMO
A field experiment was conducted to investigate the yield traits, leaf photosynthetic rate, chlorophyll fluorescence parameters, chlorophyll content (Chl), and leaf area index (LAI) of eight new big-spike wheat lines, with multiple-spike cultivar Xinong 979 (Triticum aestivum cv. Xinong 979) as the control. The eight new lines had significantly higher kernel numbers per spike, kernel qualities, and 1000-grain mass but lower spike numbers per unit area, and the lines 2036, 2037, 2038, and 2040 had significantly higher yields than the control. The average net photosynthetic rate (P(n)) of the eight new lines had no significant difference with that of the control, but the PS II maximum energy conversion efficiency, PS II actual photochemical efficiency, photochemical quenching coefficient, and PS II reaction center activity of the lines were higher than those of the control. The leaf Chl of the lines 2037, 2040, 2039, 2038 and 2036 were 17.5%, 19.1%, 15.3%, 13.9%, and 7.9% higher than those of the control, and their LAI was significantly higher than that of the control and declined slowly in late growth period.
