Penetration of naphthaleneacetic acid into pear (Pyrus communis L.) leaves

The penetration of naphthaleneacetic acid (NAA) into pear (Pyruscommunis L. cv. Bartlett) leaves as influenced by selected treatingsolution and environmental factors was studied under definedand controlled conditions. Penetration through the adaxial leafsurface was linear with time, whereas, movement through theabaxial surface was rapid initially and then the rate diminishedwith time. Penetration through both leaf surfaces was proportionalto external concentration and was temperature dependent. MoreNAA penetrated at pH values below than above the pK_a. Light(1000 ft-c) stimulated NAA penetration. The light enhanced penetrationof NAA was depressed by 3-tert-butyl-5-chloro-6-methyluracil,3-(p-chlorophenyl)-1,1-dimethylurea, phenylmercuric acetate,2,4-dinitrophenol, carbonylcyanide m-chlorophenylhydrazone andcarbonylcyanide p-trifluoromethoxyphenylhydrazone. We concludedthat NAA penetration was controlled by both physical and metabolicfactors. ¹ Journal Article No. 5725 from the Michigan Agricultural ExperimentStation. This investigation was supported-in-part by NIH TrainingGrant No. 5 TOI GM 00246 from General Medical Sciences, PublicHealth Service Grant CC 00246 from the National CommunicableDisease Center, Atlanta, Georgia, and Food and Drug AdministrationGrant FD 00223. ² Present address: Department of Plant & Soil Sciences,University of Massachusetts, Amherst, Massachusetts, 01002. (Received November 9, 1971; )     

The effect of calcium bicarbonate on iron absorption and distribution byChrysanthemum morifolium, (Ram.)

Summary Plants grown for two weeks in high-bicarbonate nutrient solution with iron became chlorotic, absorbed less iron, and translocated a lower percentage of absorbed iron than did green plants grown under low bicarbonate with iron. Chlorotic plants, pretreated in low-bicarbonate solutions lacking iron, absorbed more iron and translocated a higher percentage to leaves than the green plants. Plants induced to chlorosis by high bicarbonate absorbed less iron after transfer to low-bicarbonate solution containing iron than did chlorotic plants pretreated with low-carbonate solution lacking iron. Initial localization of iron occurred in the roots. A considerable amount of the iron initially found on the roots was translocated to developing shoots over a nine-week period unless the plants were grown in high bicarbonate solutions. More iron was translocated from roots of plants in minus-iron solutions following initial absorption than when iron was supplied in the nutrient solutions. Journal Series Paper736. University of Georgia, College of Agriculture Experiment Stations, College Station, Athens, Ga. 30601.     

Fourier transform IR study of enzymatically isolated tomato fruit cuticular membrane

Fourier transform ir study on enzymatically isolated tomato fruit cuticle has been performed. Assignments of the observed frequencies to functional groups present in the cuticular membrane yield information on the polyester cross-links and the interactions among the different components that form this plant protective barrier. © 1992 John Wiley & Sons, Inc.     

FOLIAR PENETRATION OF NAPHTHALENEACETIC ACID: ENHANCEMENT BY LIGHT AND ROLE OF STOMATA

Light enhanced the penetration of naphthaleneacetic-1-¹⁴C acid (NAA) into the stomatous lower surface of pear (Pyrus communis L. cv. Bartlett) leaf discs. The light effect was rapidly lost on transfer to the dark and was diminished by pretreatment of leaf discs with a Hill reaction inhibitor (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine). The effect of light on NAA penetration was isolated from its effect on stomatal opening. A similar stimulation of NAA penetration was obtained with stomata opened and closed, providing evidence that penetration did not take place by mass movement into the substomatal chamber.     

Preferential polar pathways in the cuticle and their relationship to ectodesmata

Summary Ectodesmata-like structures, referred to here as mercurous or mercury precipitates (MP) and considered to be identical to precipitates observed after treatment of leaf tissue with Gilson solution for demonstration of ectodesmata, were demonstrated with cuticle enzymatically isolated from Allium bulb scales and leaves mounted on ascorbic acid-enriched agar or gelatin. The MP distribution patterns obtained with isolated cuticle, in the absence of a cell wall, were identical to those observed with living tissue. Since the distribution in either the presence or absence of the cell wall was similar, the distribution pattern must be determined by the cuticle and not by the cell wall. Disruption of the physical arrangement of epicuticular wax by brushing or removal with chloroform altered the distribution pattern and increased the frequency of MP. This was interpreted to mean that epicuticular wax plays an important role and also that the necessary reductant was not localized in specific structures in the cell wall. Based on this evidence, it appears that ectodesmata, as demonstrated with Gilson solution, are not specific cell-wall structures, whether plasmic or not plasmic. More likely, the MP observed in the cell wall reflect areas in the cuticle permeable to mercuric chloride and undoubtedly to other polar compounds. The presence of such pathways in the cuticle, long established as the prime barrier to penetration of polar compounds, has marked implications in foliar uptake and excretion.Michigan Agricultural Experiment Station Journal Article No. 4971. This study was supported-in-part by Public Health Service Grant CC 00246 from the National Communicable Disease Center, Atlanta, Georgia, and Food and Drug Administration Grant FD 00223.     

Cuticular penetration of abscisic acid

Summary Penetration of 2-¹⁴C abscisic acid (ABA) through enzymatically isolated cuticles from tomato fruit and from the upper epidermis of apricot, pear and orange leaves was assessed. Penetration was linear with time, greater as the undissociated than the dissociated ion, and greater through dewaxed than non-dewaxed cuticles. Significantly less (3–6 times) (2-¹⁴C)ABA penetrated the tomato fruit cuticle than NAA or 2,4-D. The leaf cuticles were less permeable than the tomato fruit cuticle. There was no evidence that the ABA was altered during transfer across the cuticle.     

The nature of precipitates formed in the outer cell wall following fixation of leaf tissue with Gilson solution

Summary The nature of precipitates formed in the outer cell walls of leaf tissue fixed in Gilson solution, used extensively to demonstrate ectodesmata, is described. Electron-microbe X-ray analysis established that the crystalline precipitates contained both mercury and chlorine. Based on solubility in water and ethanol, birefringence and ratio of mercury to chlorine, the chemical form is probably mercurous chloride. Further treatment of the leaf tissue with potassium iodide caused the crystalline precipitate to turn black and lose birefringence when viewed with plane-polarized light. Analysis of this precipitate showed the presence of only mercury, chlorine having been lost.