Effects of elevated UV-B radiation on cuticular water permeability of ivy grown under natural or artificial light
G. Kerstiens, S.A. Moody and N.D. Paul, Biology, Lancaster University, UK.
Ivy (Hedera helix L. var. Buttercup) was grown for 10 weeks in growth cabinets (high pressure sodium lights, metal halide lights and UV-A black lights; PPFD: 0.8 mE m2 s1; 12h photoperiod plus "dawn" and "dusk" periods of 2h each). Treated plants received 6.3 kJ d1 UV-B (plant-weighted) over 10h (controls: none). This was approximately 40% more than the daily ambient clear-sky UV-B dose during summer at Lancaster. The treatment caused a significant increase in cuticular water permeance P of newly-grown leaves (+74%). Irrespective of UV-B treatment, all plants grown in this experiment showed visible signs of stress, such as slow growth and premature yellowing of leaves. Plants from the same batch kept in a greenhouse did not show these symptoms. Their P values were between those of the other two groups.
Ivy (H. helix ssp. hibernica)
was grown from May to October in a modulated field system in which
plants received additional UV-B as a percentage of incident UV-B
(see P1.18). UV-B additions were based on a model assuming an
average ozone reduction of 15% but with seasonal variation, resulting
in UV-B additions of 20-45% depending on season. Control plants
received no artificial light.. A third group of plants was grown
in a greenhouse with no supplemental UV-B. No differences in P
between any treatment were found. Plants showed no signs of stress.