Tattini Massimiliano, Montagni Giovannella, Traversi Maria Laura
Istituto sulla Propagazione delle Specie Legnose, Consiglio Nazionale delle Ricerche, Via Ponte di Formicola 76, I-50018, Scandicci, Florence, Italy.
Tree Physiol. 2002 Apr;22(6):403-12. doi: 10.1093/treephys/22.6.403.
Leaf gas exchange, water relations and osmotic adjustment were studied in hydroponically grown Phillyrea latifolia L. plants exposed to 5 weeks of salinity stress (0, 80, 160, 240 and 320 mM NaCl) followed by 5 weeks of treatment with half-strength Hoagland solution. Whole-plant relative growth rate and root/shoot and lateral/structural root ratios were also evaluated. Net CO2 assimilation rate, stomatal conductance and transpiration rate were markedly decreased by all of the salt treatments. Growth was also strongly depressed by all salt treatments, especially lateral root growth. Leaf water potential decreased soon after salinity stress was imposed, whereas there was a lag of several weeks before leaf osmotic potential decreased in response to the salt treatments. After 5 weeks of salinization, leaf turgor of salt-treated plants was similar to that of controls. Although Na+ + Cl- contributed little to the salt-induced changes in osmotic potential at full turgor (Psi(piFT)), the contributions of K+, mannitol (Man) and glucose (Glc) to Psi(piFT) markedly increased as external salinity increased. Salt accumulation was negligible in the youngest leaves, which mostly accumulated soluble carbohydrates and K+; in contrast, old leaves served as storage sinks for Na+ and Cl-. Photosynthetic performance of salt-treated plants fully recovered once salt was leached from the root zone, with the recovery rate depending on the severity of the salt stress previously experienced by the plants. Recovery of gas exchange occurred even though the leaves still had a salt load similar to that detected in leaves at the end of the 5-week salinity period, and had markedly lower concentrations of K+ and soluble carbohydrates than control leaves. We conclude that salt-induced water stress primarily controlled gas exchange of salt-treated P. latifolia leaves, whereas the salt load in the leaves did not cause irreversible damage to the photosynthetic apparatus.
研究了水培生长的宽叶福桂树植株的叶片气体交换、水分关系和渗透调节，这些植株先经受5周的盐胁迫（0、80、160、240和320 mM NaCl），随后用半强度的霍格兰溶液处理5周。还评估了整株植物的相对生长速率以及根/茎和侧根/结构根的比率。所有盐处理均显著降低了净二氧化碳同化率、气孔导度和蒸腾速率。所有盐处理也强烈抑制了生长，尤其是侧根生长。盐胁迫施加后不久叶片水势下降，而叶片渗透势响应盐处理下降则有几周的滞后。盐处理5周后，盐处理植株的叶片膨压与对照相似。尽管在完全膨压下（ΨπFT），Na⁺ + Cl⁻ 对盐诱导的渗透势变化贡献不大，但随着外部盐度增加，K⁺、甘露醇（Man）和葡萄糖（Glc）对ΨπFT的贡献显著增加。最幼嫩的叶片中盐积累可忽略不计，这些叶片主要积累可溶性碳水化合物和K⁺；相反，老叶是Na⁺ 和Cl⁻ 的储存库。一旦从根区淋洗盐分，盐处理植株的光合性能就会完全恢复，恢复速率取决于植株先前经历的盐胁迫的严重程度。即使叶片仍具有与5周盐胁迫期结束时叶片中检测到的盐负荷相似的盐负荷，并且K⁺ 和可溶性碳水化合物的浓度明显低于对照叶片，气体交换仍能恢复。我们得出结论，盐诱导的水分胁迫主要控制盐处理的宽叶福桂树叶片的气体交换，而叶片中的盐负荷并未对光合机构造成不可逆转的损害。
