| dc.description.abstract | This experiment was conducted to study the effect of high ozone concentrations on two cotton (Gossypium hirsutum L.) cultivars. Two cotton cultivars (Roma nos and Allegria) were exposed to con trol (CF < 4 ppb O(3)) and 100 ppb O(3). Plant expos ore to ozone began eight days after emergence and was interrupted one day before removing the leaves, to calculate the leaf area. Plants were exposed to ozone 7 h/day, in closed and controlled-environment chambers, during their illumination with artificial visible light. In comparison to control plants. plants exposed to O(3) showed chlorotic and necrotic patches on their leaves. increased stomatal or epidermal cell density and yellowness of cotton fibers. Elevated ozone concentration did not have a significant effect on stomatal width, total leaf thickness and thickness of histological components of leaves. Exposure to ozone concentration reduced non-glandular hair density of main leaf veins, plant height, mainstem internode length, chlorophyll content, net photosynthetic rate, stomatal conductance and length and area of bracts and petals. Elevated ozone treatment reduced the maximum length of staminal tube, anther number, pollen grain germination, leaf area, leaf dry weight, boll number, raw cotton weight, total branch length, dry weight of the mainstem-branches-bracts-carpophylls and of root dry weight. Furthermore, exposure to O(3) reduced the seed weight, the lint weight. the yield, the ratio of lint weight to seed weight, the fiber strength, the micronaire, the maturity index and the fiber uniformity index values. This study shows chat the exposure to high ozone concentrations mainly affected the rate of photosynthesis. raw cotton weight and strength of cotton fibers. (C) 2009 Elsevier B.V. All rights reserved. | en |
