Effects of ammonium nutrition on contact angle, light reflection and lightharvesting complex (LHC) of Kohlrabi leaves

Greenhouse-grown kohlrabi (Brassica oleracea var. gongylodes) cv. Express F orcer' were supplied at the same level with all nutrients, except for the f orm of nitrogen which was either nitrate or ammonium. Plants supplied with ammonium developed white-blueish glaucous leaves due to both epicuticular w ax and a dense network of wax crystals in the form of dendrites compared wi th nitrate which induced wax plates or tubes. Ammonium fertilisation induce d a larger contact angle, increased light reflection and chlorophyll conten t of the leaves, but reduced the chlorophyll a:b ratio without affecting ph otosynthesis, chlorophyll a fluorescence and transpiration relative to nitr ate-fed plants. The relationship between the increased epicuticular wax, de ndrite structures of ammonium-fed kohlrabi plants and leaf wetting is discu ssed with particular respect to pathogen infection and, similarly, the rela tion between smaller chlorophyll a:b ratio and more effective light harvest ing of the ammonium relative to the nitrate nutrition.