Growth and photosynthesis of young dwarf cashew plants grown under salt stress

Abstract Objectifying to study the responses of young cashew plants to salt stress, grafted dwarf cashew plants were irrigated with saline solutions of different electrical conductivities (ECs) applied either into the root environment or directly on the plant leaves. The electrical conductivities of drained water (ECds) practically doubled in relation to ECs, independently of the way that water was applied. Leaf Na+ and Cl- contents increased with increases of irrigation solutions, especially when applied on the leaves. When irrigation water was applied on the leaves, there were higher reductions in leaf area and leaf dry matter with salinity increase of the irrigation solution. Net photo synthesis was reduced linearly with the increase in salinity and this reduction appeared to be due mainly to stomatal limitations. The effects of salinity are more conspicuous when the irrigation solution was applied directly on the leaves, and the grafted plants appeared to acclimate better to salt stress if the saline solution was applied into the root environment.

摘要 为客观探究幼年腰果植株对盐胁迫的响应，本研究以嫁接矮生腰果植株为试验材料，采用不同电导率（EC, Electrical Conductivity）的盐溶液，分别施加于植株根系环境或直接喷施于叶片开展灌溉处理。试验结果显示，渗出液电导率（ECds, Electrical Conductivity of Drained Water）相较于灌溉溶液电导率（ECs）几乎翻倍，且该变化与供水方式无关。叶片钠离子（Na+）与氯离子（Cl-）含量随灌溉溶液盐度升高而上升，尤以直接喷施于叶片时增幅更为显著。当灌溉溶液直接喷施于叶片时，随着灌溉液盐度提升，植株叶面积与叶片干物质积累量的下降幅度显著增大。净光合速率随盐度升高呈线性下降，该抑制效应主要由气孔限制所导致。盐胁迫的影响在灌溉溶液直接喷施于叶片时更为突出；而当盐溶液施加于根系环境时，嫁接植株对盐胁迫的适应表现更佳。