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Sorption of the cytokinin N 6 ‐benzyladenine by leaf cuticles: prediction from n ‐octanol:water partition coefficients
Author(s) -
Shafer Warren E.
Publication year - 1990
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1990.tb08712.x
Subject(s) - sorption , partition coefficient , chemistry , cytokinin , ionic strength , analytical chemistry (journal) , octanol , chromatography , nuclear chemistry , adsorption , aqueous solution , organic chemistry , auxin , biochemistry , gene
Partition and sorption characteristics of the cytokinin N‐(phenylmethyl)‐lH‐purine‐6‐amine (N 6 ‐benzyladenine, BA) in two model systems were studied at 25°C. Apparent partition coefficients (K pH ) for BA in an n ‐octanol:water (buffer) system were independent of BA concentration but decreased with increasing buffer concentration (ionic strength). A plot of K pH values versus pH (2 to 12) was a bell‐shaped curve. At pH 2 or 12, K pH values were low (less than 2). As pH approached neutrality, K pH values increased approximately 20‐fold. Estimates of pK 1 (3.3) and pK 2 (10.7) values for BA were obtained from these data. The accuracy of this approach to determining pK values was verified with 2‐(1‐naphthyl)acetic acid (NAA). Correction of K pH values for dissociation effects on BA yielded partition coefficients (K) whose overall mean was 37. Sorption of BA by cuticles enzymatically isolated from abaxial and adaxial surfaces of mature rubber plant ( Ficus elastica Roxb. cv. decora) leaves was initially rapid, however equilibrium was not reached by 432 h. At pH 2, sorption was low (approximately 5 μmol kg− 1 ), whereas at pH 6 sorption increased approximately 11‐fold. Sorption by abaxial cuticular membranes (CM) and dewaxed CM (DCM) was slightly higher than corresponding adaxial CM and DCM. Using natural logarithm values, K pH data were linearly‐correlated with CM (r = 0.98) and DCM (r = 0.99) sorption data.