LOGNORMAL-DISTRIBUTION OF WATER PERMEABILITY AND ORGANIC SOLUTE MOBILITY IN PLANT CUTICLES

It is shown that water permeabilities and organic solute mobilities in plant cuticles have a lognormal distribution. Seven-hundred and fifty values for rate constants of desorption (approximate to mobility) of 2,4-D from isolated Citrus aurantium L. cuticles from a population of leaves were pooled and analysed. A histogram of the rate constants of individual cuticles showed a skew distribution with a strong tail to h igher values. Cuticular membranes with high values did not differ from others in visual appearance and were not leaky. After log-transformat ion of original data an almost perfect normal distribution was obtaine d. Statistical tests showed that a normal distribution of original val ues is not acceptable. Inspection of older data for water permeability in the same species and experiments using large samples of cuticles f rom leaves of Pyrus communis L. and Stephanotis floribunda Brongn. and from fruits of Capsicum annuum L. showed a similar distribution, as d id inspection of data for experiments with organic solutes. A lognorma l distribution was found for cuticles of plants from growth chambers, glasshouses and outdoors as well as for water permeability of intact l eaves of Hedera helix L. For small samples the overestimation from usi ng the arithmetic mean of original data can be high, but use of the ge ometric mean or the median leads to smaller deviations. Removing cutic ular waxes from cuticles produced normally distributed samples. A norm al distribution was also obtained when organic compounds which increas e solute mobility were sorbed into cuticles.