Instituto de Hortofruticultura Subtropical y Mediterránea La Mayora, Málaga, Spain.
Department of Organismic and Evolutionary Biology, Cambridge, Massachusetts, USA.
Plant Cell Environ. 2021 May;44(5):1346-1360. doi: 10.1111/pce.13985. Epub 2021 Jan 5.
Capparis odoratissima is a tree species native to semi-arid environments of South America where low soil water availability coexists with frequent night-time fog. A previous study showed that water applied to leaf surfaces enhanced leaf hydration, photosynthesis and growth, but the mechanisms of foliar water uptake are unknown. Here, we combine detailed anatomical evaluations with water and dye uptake experiments in the laboratory, and use immunolocalization of pectin and arabinogalactan protein epitopes to characterize water uptake pathways in leaves. Abaxially, the leaves of C. odoratissima are covered with peltate hairs, while the adaxial surfaces are glabrous. Both surfaces are able to absorb condensed water, but the abaxial surface has higher rates of water uptake. Thousands of idioblasts per cm , a higher density than stomata, connect the adaxial leaf surface and the abaxial peltate hairs, both of which contain hygroscopic substances such as arabinogalactan proteins and pectins. The highly specialized anatomy of the leaves of C odoratissima fulfils the dual function of minimizing water loss when stomata are closed, while maintaining the ability to absorb liquid water. Cell-wall related hygroscopic compounds in the peltate hairs and idioblasts create a network of microchannels that maintain leaf hydration and promote water uptake.
尖瓣木是一种原产于南美洲半干旱环境的树种，那里土壤水分供应不足，且夜间经常有雾。先前的研究表明，喷洒在叶片表面的水分可以增强叶片的水合作用、光合作用和生长，但叶片对水分的吸收机制尚不清楚。在这里，我们结合详细的解剖评估以及实验室中的水分和染料吸收实验，使用果胶和阿拉伯半乳聚糖蛋白表位的免疫定位来表征叶片中的水分吸收途径。在叶片的背面，尖瓣木覆盖着具柄的毛，而叶的正面则无毛。两个表面都能够吸收凝结水，但背面的吸收速度更高。每平方厘米有数千个离体细胞，其密度高于气孔，将叶片的正面和背面的具柄毛连接起来，这两个部位都含有亲水性物质，如阿拉伯半乳聚糖蛋白和果胶。尖瓣木叶片高度特化的解剖结构实现了双重功能，既能在气孔关闭时最大限度地减少水分流失，又能保持吸收液态水的能力。具柄毛和离体细胞中的细胞壁相关亲水性化合物形成了一个微通道网络，维持叶片水合作用并促进水分吸收。
