NaCl渐进胁迫对啤酒大麦幼苗生长、离子分配和光合特性的影响

砂培条件下,对啤酒大麦幼苗在等量NaCl 梯度(每周以17.1 mmol/L NaCl递增)渐进胁迫下生长和生理的响应进行研究。结果表明,随着盐浓度的递增,啤酒大麦地上生物量、株高显著低于对照组,而根系生物量和根冠比高于对照组,低盐分、短时间盐胁迫能刺激根系生长。盐分胁迫至高浓度(≥85.5 mmol/L NaCl)时,随着胁迫时间的持续,大麦幼苗生长受到抑制,地上含水量明显下降;短时间内适应低浓度盐胁迫后,一定程度上提高了啤酒大麦的净光合速率(P_n),而高浓度盐分能显著抑制大麦的净光合速率,气孔导度(G_s),胞间CO₂浓度(C_i)和蒸腾作用(T_r);高浓度、长时间盐分渐进胁迫下,影响大麦光合特性的主要是非气孔因素。大麦地上部Na⁺和Cl^-含量随介质中NaCl浓度的递增和胁迫时间的延续呈逐渐上升趋势,而根系中Na⁺含量呈下降趋势,Cl^-含量则呈逐渐上升的趋势。处理组大麦地上部K⁺/Na⁺明显低于对照,且随着盐浓度的递增而减小,说明在盐分胁迫过程中,地上部分优先积累 Na⁺。选择性吸收和运输K⁺是啤酒大麦适应渐进盐胁迫的生理生态机制。

Effect of extended exposure to NaCl stress on the growth,ion distribution and photosynthetic characteristics of malting barley (Hordeum vulgare)

The adaptation mechanism of malting barley (Hordeum vulgare) growth response and ion distribution elicited by extended exposure to NaCl stress were investigated by simulating the formation process of soil salinisation in arid and semi-arid irrigated regions. The objective was to provide the theoretical basis for increasing the yield of malting barley and rationally employing the salt-affected arable land in irrigated agricultural systems. Seedlings of malting barley were treated by adding NaCl to the growth medium to gradually increase the concentration in 17.1 mmol/L increment every week during the vegetative period until a concentration of 154.9 mmol/L was reached. Nine harvests (7 d after treatment) were analysed to examine plant growth, root growth parameters, ion contents, and photosynthetic characteristics. The growth rate of barley seedlings was inhibited by extended exposure to NaCl. Under salinity stress the shoot biomass and height decreased significantly in comparison with the control, but the root biomass and root/shoot ratio increased significantly with extended exposure to NaCl. In addition, root length increased at lower salt concentrations with a short incubation period. At higher NaCl concentrations (≥85.5 mmol/L NaCl), salt stress seriously inhibited the growth of the seedlings and the water content of malting barley was seriously decreased. Furthermore, with an increase in salt stress level, photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and transpiration rate (T_r) were significantly reduced. This was strongly dependent on the appearance of non-stomatal limitation to photosynthetic characteristics imposed by long-term induced salinity stress. Under extended exposure to NaCl stress, Na⁺ and Cl^- content in shoots increased significantly, whereas in roots, Na⁺ content increased but Cl^- content decreased with the extension of incubation days. Compared with the controls, the K⁺/Na⁺ in shoots significantly decreased as NaCl concentration increased. Malting barley accumulated much more Na⁺ in shoots by selectively absorbing K⁺ under intense salt stress. The selective absorption and transportation of K⁺ were the key adaptive mechanism of high salt-tolerance of malting barley.