Abstract To understand the adaptive strategies employed by plants to deal with saline conditions, two halophytic species [Chenopodium quinoa (quinoa) and Beta maritima (sea beet)] and their glycophytic relatives [Chenopodium album and Beta vulgaris (sugar beet)] were grown under 0−500 mM salt concentrations followed by the comprehensive assessment of their agronomical, ionic, gas exchange characteristics. Salinity levels up to 300 mM NaCl had no adverse effect on quinoa biomass and 200 mM NaCl stimulated sea beet growth. Stomatal conductance decreased in a dose-dependent manner in all species with increasing NaCl concentrations. However, CO2 assimilation rates remained constant or displayed higher values at the medium level of salinity (100−200 mM NaCl) in quinoa, sugar beet and sea beet. High maximum carboxylation rate of Rubisco (Vcmax) and higher rate of electron transport through photosystem II (J) were responsible for the high photosynthetic rates and biomass productions under these conditions. Both characteristics were much higher in halophytic species for the given external NaCl level. Stomatal densities were intrinsically lower in halophytic species (14–34%); these increased with increasing salinity levels in the sugar beet and sea beet while C. album and quinoa stomata remained less dense under saline conditions. Stomata responses to environmental stimuli were much faster in halophytes (16.6–49.7%), and substitution of K+ by Na+ resulted in promotion of stomatal opening under 50 mM NaCl and 50 mM KCl in quinoa. It is concluded that superior salinity tolerance in halophytes is achieved by significantly faster stomatal opening and closure, their ability to discriminate K+ over Na+, and uncoupling of CO2 assimilation from changes in stomatal aperture.

中文翻译：

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盐分条件下密切相关的盐生植物和糖生植物的气孔性状和光合反应的比较分析

摘要 为了了解植物应对盐碱环境的适应性策略，两种盐生植物 [Chenopodium quinoa (quinoa) 和 Beta maritima (sea beet)] 及其糖生近缘种 [Chenopodium album 和 Beta vulgaris (sugar beet)] 在0-500 mM 盐浓度，然后对其农艺、离子、气体交换特性进行综合评估。高达 300 mM NaCl 的盐度水​​平对藜麦生物量没有不利影响，而 200 mM NaCl 会刺激海甜菜生长。随着 NaCl 浓度的增加，所有物种的气孔导度均以剂量依赖性方式降低。然而，在藜麦、甜菜和海甜菜的中等盐度（100-200 mM NaCl）下，CO2 同化率保持不变或显示出更高的值。Rubisco 的高最大羧化速率 (Vcmax) 和通过光系统 II (J) 的更高电子传输速率是这些条件下高光合速率和生物质产量的原因。对于给定的外部 NaCl 水平，两种特征在盐生植物中都高得多。盐生植物的气孔密度本质上较低（14-34%）；这些随着甜菜和海甜菜盐度水平的增加而增加，而在盐度条件下，C.album 和藜麦气孔的密度仍然较低。在盐生植物中，气孔对环境刺激的反应要快得多（16.6-49.7%），并且在藜麦中，在 50 mM NaCl 和 50 mM KCl 下，用 Na+ 替代 K+ 会促进气孔开放。