Arbeitsgruppe Membranforschung am Institut für Medizin, Kernforschungsanlage Jülich GmbH, Postfach 1913, D-5170, Jülich, Federal Republic of Germany.
Planta. 1983 Jan;159(1):38-45. doi: 10.1007/BF00998812.
All of the cells of the upper (adaxial) epidermis of the leaves ofOxalis carnosa are transformed into large bladders, while in the lower epidermis the bladder cells are interrupted by "normal" cells with stomata. The epidermal bladders contain a high concentration of free oxalic acid (pH approx. 1). Water-relations parameters of these epidermal bladder cells have been determined using the pressure probe. Original cell turgor (P0) of the closely packed bladders of theupper epidermis was P0=0.7 to 2.9 bar ([Formula: see text]; mean±SD;N=25 cells) and lower than that in the club-shaped bladders of thelower epidermis (P0=1.3 to 3.7 bar;[Formula: see text];N=25 cells). Large differences in the elastic modulus (ε) and the hydraulic conductivity (Lp) of the two different types of cells were observed. For the lower epidermal bladders, ε=18 to 166 bar and was similar to that of other higher plant cells. Also, for these cells it was found that ε was increasing with both, cell turgor and cell volume. By contrast, ε of the cells of the upper epidermis was by one order of magnitude smaller (ε=1.9 to 17.0 bar) and no dependence of ε on cell volume could be detected. The Lp values of the cell membranes were also different (lower epidermis:[Formula: see text]; upper epidermis:[Formula: see text]). These differences seem to be too large to be caused by errors in determining the exchange area for water (A) between cells and adjacent tissue. The half-times of water exchange between bladders and leaf (T1/2) were, on average, somewhat longer for the upper than for the lower epidermis (lower epidermis: T1/2=7 to 38 s; upper epidermis: T1/2=22 to 213 s), but the differences in the T1/2 values were not as distinct as for ε and Lp. This is because of the compensatory effects of ε, Lp and the different ratios of volume to exchange area. Since the bladders make up about 75% of the entire volume of the leaf, it is assumed that the rate of response of the leaf to changes in the water potential should be similar to that of the bladder cells. The results are discussed in terms of a possible function of the bladders in the leaf.
叶片上表皮（近轴面）的所有细胞都转化为大型泡囊，而下表皮的泡囊细胞则被具有气孔的“正常”细胞隔开。表皮泡囊中含有高浓度的游离草酸（pH 约为 1）。使用压力探针测定了这些表皮泡囊细胞的水分关系参数。上表皮紧密排列的泡囊的原始细胞膨压（P0）为 P0=0.7 至 2.9 巴（[公式：见正文]；均值±SD；N=25 个细胞），低于下表皮棒状泡囊的 P0=1.3 至 3.7 巴（[公式：见正文]；N=25 个细胞）。观察到两种不同类型细胞的弹性模量（ε）和水力传导率（Lp）存在较大差异。对于下表皮的泡囊，ε=18 至 166 巴，与其他高等植物细胞相似。此外，还发现这些细胞的 ε 值随着细胞膨压和细胞体积的增加而增加。相比之下，上表皮细胞的 ε 值小一个数量级（ε=1.9 至 17.0 巴），并且不能检测到 ε 值与细胞体积之间的依赖关系。细胞膜的 Lp 值也不同（下表皮：[公式：见正文]；上表皮：[公式：见正文]）。这些差异似乎太大，不可能是由于细胞和相邻组织之间水交换面积（A）的测定误差引起的。泡囊与叶片之间水分交换的半衰期（T1/2）平均值对上表皮比下表皮稍长（下表皮：T1/2=7 至 38 s；上表皮：T1/2=22 至 213 s），但 T1/2 值的差异不如 ε 和 Lp 值明显。这是因为 ε、Lp 和体积与交换面积的不同比例的补偿效应。由于泡囊占叶片总容积的 75%左右，因此可以假设叶片对水势变化的响应速度应该与泡囊细胞相似。结果根据泡囊在叶片中的可能功能进行了讨论。
