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1.
Calcium chloride penetrates plant cuticles via aqueous pores 总被引:2,自引:0,他引:2
Schönherr J 《Planta》2000,212(1):112-118
Penetration of calcium chloride across astomatous cuticular membranes (CMs) isolated from leaves of Pyrus communis L. has been studied. Penetration was a first-order process when calcium chloride concentrations ranged from 2 g l−1 to 10 g l−1. Rate constants were increased 10-fold by adding wetting agents but they did not depend on temperature. The accelerators
tributyl phosphate and diethyl sebacate had no effect on rates of penetration. Increasing humidity over the salt residue on
the CMs from 50 to 90% increased rate constants by about 2-fold. Extracting cuticular waxes from pear leaf CMs increased rate
constants by factors of 2 to 3, depending on humidity. Leaf CMs from Malus domestica Borkh., Populus alba L., Stephanotis floribunda Brongn. and Schefflera actinophylla (Endl.) Harms were also permeable to CaCl2. Highest rate constants were observed with poplar CMs while Schefflera CMs exhibited the lowest permeability. By comparing these results with the well established transport properties of the lipophilic
pathway it is concluded that calcium chloride hexahydrate penetrated cuticular membranes via aqueous pores.
Received: 14 December 1999 / Accepted: 31 March 2000 相似文献
2.
Solute mobility in cuticular membranes (CMs) of 14 plant species (Citrus aurantium L., Citrus grandis L., Hedera helix L., Ilex aquifolium L., Ilex paraguariensis St.-Hil., Malus domestica Borkh. cv. Golden Delicious, Populus alba L., Prunus laurocerasus L., Pyrus communis L. cv. Bartlett, Conference and Gellerts Butterbirne, Pyrus pyrifolia (Burm. f.) Nakai, Schefflera actinophylla (Endl.) Harms and Strophanthus gratus Baill.) was measured over the temperature range 25–55 °C. The five organic model compounds differed in size (130–349 cm3 mol−1) and cuticle/water partition coefficient (18–108). For all individual CMs (n = 297), the data were plotted according to the thermodynamic relationship between the preexponential factor (which is proportional
to entropy) of the Arrhenius equation and the activation energy (enthalpy) of diffusion (E
D
). A strict linear correlation was obtained, providing evidence that the five compounds diffused along the same lipophilic
diffusion path in all plant species tested. Extracting cuticular waxes from CMs of four plant species (Hedera, Pyrus, Schefflera and Strophanthus) had no effect on the slope of the plot but a parallel displacement towards higher entropy was observed with these polymer
matrix (MX) membranes. This displacement is interpreted as a temperature-independent tortuosity factor directly related to
entropy. The influence of the plasticiser tributyl phosphate on solute mobility at various temperatures was measured for CM
and MX membranes. The plasticiser increased solute mobility and E
D
was reduced drastically for both membrane types. This plasticiser effect was almost completely reversible, when tributyl
phosphate was desorbed from the membranes. For both, plasticised CM and MX, the thermodynamic correlation exists whereby all
data points lie on the same line. The data are used to characterise the lipophilic pathway across plant cuticles in terms
of the free-volume theory.
Received: 14 December 1999 / Accepted: 31 March 2000 相似文献