Many undergraduates major in horticulture because they love working with plants. When they hear research that documents how people respond-to plants, some students -begin to understand why they have responded positively to plants, and they want to learn more about the topic. This paper 1) discusses the potential to use students' excitement about human issues in horticulture to teach principles that educators consider important components of a baccalaureate degree, and 2) presents the case of one student to demonstrate how it can be done.
Abstract
N-[2-(2-oxo-l-imidazolidinyl)ethyl]-N’-phenylurea, (EDU or ethylenediurea) reduced the sensitivity of petunia plants (Petunia hybrida Vilm.) to ozone when treated with foliar or root applications. For most plants, EDU gave protection from visible injury within 24 hours of its application as a spray or soil drench. It was much more effective than butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) as a protectant from ozone injury. The activity of EDU was unaffected by the addition of a surfactant to the spray solution or soil drench, by day length, light conditions, temperature, and physiological preconditioning of the plants. Protection from injury by ozone lasted for at least 14 days. Furthermore, a concentration of 500 ppm either as a foliar spray of 1 to 2 ml per plant or as a soil drench of 100 ml per 10-cm diameter pot protected an ozone sensitive cultivar, ‘Snow Magic,’ the moderately sensitive cultivars, ‘White’ and ‘Pink Cascade,’ and the least sensitive cultivars, ‘Comanche Improved’ and ‘Sugar Plum’. Treatment with EDU afforded no protection against sulfur dioxide exposure doses which produced acute injury.
Abstract
Three separate experiments were conducted in a mature Vitis labruscana Bailey ‘Concord’ vineyard in New York to determine the response of grapevines to daily, season-long sulfur dioxide (SO2) exposure, or to intermittent SO2 exposure simulating emissions from a 1700 MW coal-fired power plant. There was little SO2-induced necrosis on grape foliage from daily or power plant SO2. However, both treatments in ambient air increased susceptibility of leaves to oxidant stipple injury due to ambient ozone (O3). Daily SO2 increased leaf chlorosis. Power plant SO2 had no effect on vine growth, yield, or shoot maturation. Daily SO2 reduced soluble solids, growth, yield, and shoot maturation of grapevines. Damage to grapevines from SO2 seemed to be independent of SO2 induced leaf necrosis. SO2 reduced foliage tolerance to O3 injury in grapevines already stressed by ambient O3.
Abstract
Mature grapevines (Vitis labrusca L. cv. Concord) in a factorial experiment testing effects of nitrogen fertilization, rootstock, flower cluster thinning, weed control, and pruning severity were evaluated for oxidant injury in 1971, 1972, and 1973. Nitrogen at 56 and at 112 kg/ha, own-rooted vines, and flower-cluster thinning reduced the incidence of oxidant stipple over no nitrogen, vines grafted on Couderc 3309 rootstock, and no thinning, respectively. In 1971, a relatively dry growing season, vines in clean-cultivated plots showed less oxidant injury than vines in sod plots. Pruning severity and training system had no influence on oxidant stipple development. Total N concentration of tissue was negatively correlated to oxidant stipple severity. The interactions between flower cluster thinning and weed control, rootstock, and N fertilization were significant, where thinning moderated the deleterious effects of these factors.
Abstract
Fifty-nine American, 40 Frency hybrid, and 6 Vitis vinifera L. grape cultivars growing in vineyards at Geneva, N.Y., were rated 4 consecutive years at mid-September for oxidant stipple injury from ambient ozone. There were significant differences in injury among the American and French hybrid cultivars. Cluster analysis separated the American cultivars into 3 sensitivity groups and the french hybrids into 2 sensitivity groups. American cultivars had the highest variability among cultivars in sensitivity, with Ives and Couderc 3309 having the highest sensitivity. High sensitivity to ozone as evidenced by oxidant stipple injury appears to originate within the American Vitis species. None of the cultivars examined was resistant to ambient ozone.
Abstract
A simple, inexpensive method is presented to prepare an effective chemical scrubber which oxidizes volatile organic contaminants in gases. The scrubber is made by mixing 100 ml of 1 M KMnC4 per liter of dust-free Perlite in a large clear plastic bag.
A series of experiments were conducted to determine the sensitivity of radish to four light alcohols (ethanol, methanol, 2-propanol, and t-butanol) identified as atmospheric contaminants on manned spacecraft. Radish (Raphanus sativus L. `Cherry Bomb' Hybrid II) seedlings were exposed for 5 days to concentrations of 0, 50, 100, 175, 250, and 500 ppm of each alcohol and the effect on seedling growth was used to establish preliminary threshold response values. Results show a general response-pattern for the four alcohol exposures at threshold responses of 10% (T10), 50% (T50) and 90% (T90) reduction in seedling length. There were differences in the response of seedlings to the four alcohols, with the T10 for t-butanol and ethanol (25 to 40 ppm) being 3 to 5× lower than for methanol or 2-propanol (110 to 120 ppm). Ethanol and t-butanol exhibited similar T50 values (150 to 160 ppm). In contrast, T50 for methanol (285 ppm) and 2-propanol (260 ppm) were about 100 ppm higher than for ethanol or t-butanol. Chronic exposures to 400 ppm t-butanol, ethanol or 2-propanol were highly toxic to the plants. Radish was more tolerant of methanol, with T90 of 465 ppm. Seeds did not germinate at the 500 ppm treatment of t-butanol, 2-propanol, or ethanol. There were significant differences in projected performance of plants in different environments, dependent upon the regulatory guidelines used. The use of exposure guidelines for humans is not applicable to plant systems.
Abstract
Lettuce (Lactuca sativa L. cv. Grand Rapids) and radish (Raphanus sativus L. cv. Cherry Belle) plants growing at baseline environmental conditions were exposed to charcoal-filtered air, 0.40 ppm (v/v) ozone, and 0.80 ppm sulfur dioxide alone or in combination for 6 hours at 14 days from seeding. Analysis of covariance was used to account for significant within-treatment variation in plant growth. Covariates used were: planar leaf area (PLA) at 14 days for leaf area, fresh weight, and dry weight at harvest; plastochron index (PI) at 14 days for PI at harvest; and hypocotyl diameter for hypocotyl weights of radish roots at harvest. The covariates reduced the variability (standard geometric errors) of the response variables and increased the precision of statistical tests substantially for lettuce but much less for radish. For lettuce, the effect of the gas mixture on plant growth and foliar injury was less severe than that of the single gases. Radish plants, in contrast, exhibited no response to SO2 and the effects of O3 and the mixture on foliar injury and plant growth were similar.
Cucumis sativus L. (cvs. Poinsett and Ashley) plants were grown from seed in a growth chamber at a +10C (28/18) or a -10C (18/28) difference (DIF) between day temperature (DT) and night temperature (NT) on a 12-hour photoperiod for 24 days prior to ozone (O3) fumigation (3 hours at 0.5 umol·mol-1). Negative DIF, compared to +DIF, reduced plant height, node count, fresh weight, dry weight, and leaf area in both cultivars. Photosynthetic rate (Pn), chlorophyll concentration, and variable chlorophyll fluorescence (Fv) were lower and O3 injury and polyamine concentrations were higher at -DIF than at +DIF. Ozone fumigation generally increased leaf concentration of polyamines and reduced Pn, stomatal conductance, and chlorophyll fluorescence. `Poinsett' generally had a higher specific leaf mass and higher concentrations of chlorophyll a and polyamines than did `Ashley', but there was no cultivar difference in O3 injury, growth response, Pn, or stomatal conductance.
Abstract
The importance of monitoring air pollutants has been dramatically emphasized by the occurrence of killer smogs in major cities throughout the world. However, many other valid reasons exist for monitoring air pollutants. Nearly 40 years ago the United States and Canada were entangled in an air pollution controversy which emphasized that air pollutants ignore national boundaries. There is nothing to stop the estimated 264 million tons of air pollutants discharged annually in the United States from wandering over neighboring borders. Such a trip is even facilitated by the fact that almost 90% of this air pollution is invisible. As horticulturists, we are most concerned about air pollution effects on plants. Crop losses in the United States due to air pollution amount to approximately 500 million dollars annually. Some of this damage may come from pollutants generated outside the United States. However, air pollutants generated in the United States have been responsible on several occasions for crop damage in Canada. Scandinavian and other countries sharing common borders often share their air pollutants just as North Americans do. Fifteen years ago a World Health Organization publication indicated that sampling, analysis, and instrumentation in the field of air pollution monitoring was in a state of chaos. This symposium will show that out of the chaos has come order and that the science of monitoring air pollutants has become quite sophisticated and most complex, though many problems still remain to be solved. As an example, during the past year a disagreement on how to measure air pollution in California was reported on prime time television in the United States. Problems such as this are discouraging and most unfortunate. Nonetheless, they illustrate the heart of the air pollutant monitoring problem, which is that man has become biologically obsolete in sensing pollution hazards and we must develop new and more accurate methods and sensitive instruments to detect these hazards for ourselves, our animals, and our plants if life is to survive.