Effects of Simulated Acid Rain on Production, Morphology and Composition of Epicuticular Wax and on Cuticular Membrane Development

Abstract

SUMMARYLeaves of Phaseolus vulgaris L., Vicia faba L., Pisum sativum L. and Brassica napus L. were exposed to simulated rain from emergence to full expansion at seven pHs between 56 and 26, applied at 2 mm h"^ in amounts and at intervals representative of ambient rain in southwestern England. Leaf expansion was unaffected by rain pH greater than 30 in V.faba, and pH 2 6 in the other species. Macroscopic foliar injury was induced at pH ^ 34 in non-wettable leaves of P. sativum and B. napus which had relatively large deposits of crystalline epicuticular wax, and at pH 3-0 in wettable leaves of P. vulgaris and V. faba which had small deposits of amorphous wax. Foliar injury was greatest in species with crystalline wax. Wax production was affected by simulated acid rain in all species and was often accompanied by changes in wax composition. Wax quantity was reduced on leaves of P. vulgaris exposed to rain at pH ^ 4 6, while wax on leaves of P. sativum and B. napus had increased numbers of smaller plates and tubes, respectively, per unit area at pH ^4 6. Leaves of B. napus, stripped of crystalline epicuticular wax at about 20% full expansion, regenerated less wax at pH 3 4 than at pH 5 6. The thickness of the cuticular membranes in leaves of P. vulgaris, V.faba and P. sativum exposed to simulated acid rain at pH < 4 2 decreased by 28 to 35 % compared with those exposed to pH 5 6 rain. Membrane ultrastructure was also altered in leaves of P. vulgaris. Taken together, these changes could have important consequences for leaf wettability, rainfall retention, foliar uptake of chemicals and host-parasite interactions.

Effects of acid, or ammonium‐enriched, artificial mist on leaf blight of London plane [Platanus×acerifolia (Ait.) Willd.] and on the behaviour of the causal fungus, Apiognomonia veneta (Sacc. & Speg.) Höhn.

“…FI, most probably originating from the leaf itself, might have reached the surface mainly by diffusion from the inner tissues, or as a constituent of wax or the cuticular layer (Martin & Juniper, 1970;Holloway, 1982). It has been found by Percy & Baker (1987, 1988) that exposure of herbaceous legumes to acid rain treatments with a pH above that used in our experiments resulted in a reduction of wax production, thinning of the cuticular membrane, and an increase of leaf wettability. Thus, leaching of FI might have been promoted by the eroding activity of acid mist A. Additionally, the similarity of effects of both mist A and N on the anti-fungal activity of leachates could be a consequence of their content of cations capable of displacing exchangeable cations of the leaf.…”

“…Nevertheless, it has to be remembered that the acidity and total ion concentration of mists A and N used here can easily be exceeded by values encountered in the field. Lesion development and erosion of leaf and needle surfaces can be induced at pH < 3-5 (Evans, Gmur & de Costa, 1978;Percy & Baker, 1987); conversely, high ion concentrations in precipitation may have a fertilizing effect (Clarkson, Kuiper & Luttge, 1986). Thus, it seems possible that exposures of plane leaves to mists possessing a lower pH and a higher mineral content than those used in our study may cause more severe alterations of susceptibility to leaf blight.…”

Differences in Epicuticular Wax Layer in Tulip Can Influence Resistance to Botrytis Tulipae

“…It is important to mention that the amount and chemical composition (related to the morphology) of epicuticular wax is known to be affected by growing conditions such as temperature, relative humidity, irradiance and by wind (Percy and Baker, 1987). This means that future studies need to take growing conditions in account in order to elucidate under which circumstances the amount of wax layer is formed or/and which chemicals are produced in order to inhibit Botrytis infection in tulips.…”

Extreme climatic events: impacts of drought and high temperature on physiological processes in agronomically important plants

“…The cuticle is situated at the interface between the plant and its atmospheric environment. It is continuously exposed to natural and anthropogenic influences (Percy and Baker, 1987). Air pollutants and other environmental stresses may induce deposition of cuticular waxes which results in morphological changes to epicuticular wax layers.…”