Greger Maria, Johansson Monica, Stihl Alvar, Hamza Karim
Dept of Botany. Stockhoim Univ., S-106 91 Stockholm, Sweden.
Physiol Plant. 1993 Aug;88(4):563-570. doi: 10.1111/j.1399-3054.1993.tb01372.x.
Pea (Pisum sativum L. cv. Fenomen) and sugar beet (Beta vulgaris L. cv. Monohill) were cultivated in nutrient media without or with 10 μM CdCl . Leaves of the same size and stage of development, detached or still attached to the intact plants, were submerged into redistilled water containing 1 to 250 μM CdCl . The uptake experiments were run for 1 to 8 h at pH 3.6 and 5.1. Cuticular transpiration rate, density of leaf and density of stomata were also measured. Percentage of open stomata was studied at different pH. Foliar uptake of Cd into the leaf is evident since Cd is transported from the exposed part of the pea leaves, through the petioles and into the stipules, and since the Cd concentration of the leaves increases with time and external Cd concentration. The foliar uptake depends on the permeability of the cuticular membrane, which is increased by a high intrinsic Cd level, which in turn enhances the foliar uptake of Cd in sugar beet. Higher cuticular permeability in pea than in sugar beet is shown by a 2.5 times higher cuticular transpiration rate and a 4 times lower density of leaf for pea, which causes a 7 times higher foliar uptake in pea than in sugar beet. Low pH decreases the net uptake of Cd, probably by an exchange reaction in the cutin and pectin of the cuticular membrane. Stomata are not directly involved in the Cd uptake, and the differences in the sum total of stomatal aperture area per unit leaf area is not related to differences in foliar uptake of Cd. Percentage of open stomata, calculated as average of both sides of the leaves, was not affected by changes in pH: but especially at high pH. proportionally more stomata were open on the adaxial than on the abaxial side.
豌豆（Pisum sativum L. cv. Fenomen）和甜菜（Beta vulgaris L. cv. Monohill）种植于不含或含有10 μM CdCl₂ 的营养培养基中。将相同大小和发育阶段的叶片，无论是从完整植株上摘下的还是仍附着在植株上的，浸入含有1至250 μM CdCl₂ 的重蒸馏水中。吸收实验在pH值为3.6和5.1的条件下进行1至8小时。还测量了角质蒸腾速率、叶片密度和气孔密度。研究了不同pH值下开放气孔的百分比。由于镉从豌豆叶片的暴露部分通过叶柄运输到托叶中，并且叶片中的镉浓度随时间和外部镉浓度的增加而增加，所以镉通过叶面吸收进入叶片是明显的。叶面吸收取决于角质膜的通透性，高内在镉水平会增加角质膜的通透性，进而增强甜菜对镉的叶面吸收。豌豆的角质蒸腾速率比甜菜高2.5倍，叶片密度比甜菜低4倍，这表明豌豆的角质膜通透性高于甜菜，导致豌豆的叶面吸收比甜菜高7倍。低pH值可能通过角质膜中角质和果胶的交换反应降低镉的净吸收。气孔不直接参与镉的吸收，单位叶面积气孔孔径总面积的差异与镉叶面吸收的差异无关。以叶片两面的平均值计算的开放气孔百分比不受pH值变化的影响：但特别是在高pH值时，近轴面开放的气孔比例比远轴面成比例地更多。
