Search Results
Abstract
Eighteen cultivars representing 6 species (Poa pratensis L., Agrostis alba L., Agrostis palustris Huds., Agrostis tenuis Sibth., Festuca rubra Gaud., and Lolium perenne L.) of cool season turfgrass were exposed to 15 pphm ozone for 6 hours daily, 15 pphm sulfur dioxide continuously, 15 pphm nitrogen dioxide continuously, or a mixture of all three at these concentrations for 10 days. The most common symptoms of injury on sensitive cultivars in response to these gases were bleaching and necrosis of leaves with some cultivars exhibiting dark brown necrosis and stippling in response to O3 alone. Cultivars varied in sensitivity to O3 or SO2 from very sensitive to insensitive while few cultivars were sensitive to NO2 alone at the concentration used. Exposure of some cultivars resulted in less leaf area production but no visible injury symptoms, while other cultivars had leaf injury without reduction of area of uninjured leaves. The combined exposure caused more leaf injury and greater reduction in the leaf area production by most cultivars compared with plants exposed to single gases. Exposure to single pollutants could provide inaccurate estimates of turfgrass cultivar sensitivity outdoors where several pollutants may occur simultaneously.
Abstract
Excised shoots of 10 shade tree species were exposed for 6 hours to 40 pphm (vv−1) sulfur dioxide (SO2), 40 pphm nitrogen dioxide (NO2), or 25 pphm ozone (O3) separately or in mixture. Sorption rates were generally greater in coniferous than in deciduous shoots and higher for SO2 than NO2. Adsorption on leaf surfaces was greater than absorption through stomates for 4 of 5 species in which the 2 forms of sorption could be separated, while sorption from single gases was similar to that from mixed gases for these species. For the 5 species in which transpiration continued in darkness, sorption from the mixture was consistently less than from single gases.
Abstract
Under the light microscope the stomata of 3 cultivars of Petunia hybrida Vilm. were similar in shape and type. However, scanning electron microscopic examination of ‘White Cascade’ petunia (O3 sensitive) revealed guard cell cuticle was not raised above the epidermal surface. ‘Capri’ (O3 insensitive) had the greatest number of stomata/mm2 and the shortest pore length whereas ‘White Cascade’ had the lowest number but the longest pore length. The cultivar with intermediate O3 sensitivity, ‘White Magic’, had an intermediate stomatal density and pore size. The stomatal pore area (mm2/mm2 leaf surface area) was found to be about equal in all 3 cultivars. ‘Capri’ had many more trichomes per unit area than ‘White Cascade’ while ‘White Magic’ had intermediate numbers. No major differences existed in leaf diffusive resistance among the cvs. in either light or dark. The O3 insensitivity of ‘Capri’ was not explained by inherently fewer stomata and/or smaller stomatal size and/or greater leaf diffusive resistance than those of the sensitive ‘White Cascade’. Number of trichomes, sizes of epidermal cells and configuration of guard cell cuticle in relation to epidermal cells may be related to sensitivity.