1 To whom reprint requests should be addressed. Dept. of Botany and Plant Sciences and Statewide Air Pollution Research Center, Univ. of California, Riverside. 2 Dept. of Viticulture and Enology, Univ. of California, Davis. The cost of
Air pollution may play a role in gametophytic selection. To estimate whether such selection was occurring, pollen grains from homozygous and heterozygous tomato plants were tested under pollution stress. Homozygous pollen could be expected to respond to pollution more uniformly than heterozygous due to the identical genotype of the pollen grains. Acid rain reduced pollen germination and tube elongation in Lycopersicon hirsutum LA1777 (heterozygous) and Lycopersicon pennellii LA716 (nearly homozygous). UV-B reduced tube length of the pollen from both plants, but ozone only reduced pollen tube length of L. pennellii. The responses of these two kinds of pollen to acid rain, ozone, and UV-B appears to be same in terms of heterozygosity and stress dosages, suggesting the reduction of pollen germination and tube elongation under pollution stress may be mediated through physiological or physical alterations and not a response of different genotypes.
Urban horticulture is an emerging area of interest to the researcher, teacher, landscape architect, city planner, forester, nurseryman, and the public. In today's society, demands are made on plants and man which are often above and beyond anything that could be considered normal for the species. The human animal is expected to work efficiently and effectively amidst austere surroundings of glass and concrete of major cities and to “relax” in busy, often sunless streets. In order to improve this working environment, planners and architects recommend a greater use of plants, the benefits of which have been provided for us by many of the early researchers in design and greenspace architecture. Trees and other woody plants improve the urban environment by screening unwanted views, by reducing noise and air pollution, and by generally improving the well-being of the individuals who come in contact with them. However, we often fall short of success in our search for suitable plants for use in the urban environment.
Air pollutants are ubiquitous to man’s environment and their impact on society is particularly evident in the most highly industrialized regions and the most densely populated urban communities. Injurious effects of some of these pollutants were observed and reported in the literature as early as the mid-19th century. These early observations were concerned basically with symptoms of acute injury manifested by severe chlorosis, growth distortion, necrotic lesions, and even death of large numbers of plants. Attention was focused on regions where high concentrations of toxic materials occurred frequently and plant communities were exposed to severe dosages. More recently, agriculturists, plant researchers, and air pollution control agencies recognized that visible symptoms are evidence of acute injury but a significant impact of pollutants on the total plant ecosystem may occur in the absence of readily recognizable visible evidence. Attempts to assess economic loss due to air pollutants have been based largely on an evaluation of the overall effect of varying degrees of visible injury, and for lack of information, have usually been forced to ignore injury without visible symptoms.
Rapid screening techniques for selecting salt-tolerant plants are heretofore untried, untested, or unproven. Theoretically, we know it is possible to screen plants for this trait. Halophytes and salt-tolerant ecotypes exist in nature and variability in tolerance has been demonstrated in a number of agronomic species (48). However, the complexities of salt tolerance and the multitude of ways in which plants adjust and adapt to it have caused much confusion. The effect of salinity on a plant may depend on ontogeny (3, 11), humidity (21, 22, 34), temperature (21, 35), light (14, 35), irrigation management (8, 9), cultural practices (6, 11), soil fertility (10, 32), air pollution (20, 26), and the particular growth or yield parameter measured (3, 49). If all environmental conditions are optimal it is possible to grow some agricultural crops at seawater salinity concentrations. Barley, wheat, millet, and various other crops have been grown on sandy beach areas using seawater for irrigation (4, 5, 16, 24). The use of sand facilitates leaching and minimizes salinity accumulation. Additionally, coastal areas may be cool and humid, and, if fogs are common, have low light intensities. These factors create a favorable environment and decrease salinity damage. Recently, Epstein and colleagues used such an environment to screen a barley composite for salt tolerance (16). Several lines were selected which seemed to produce higher yields than the test cultivars. It is possible that such research will result in the selection of traits that will enhance salt tolerance in barley cultivars adapted to other environments.
More than 70 biogenic hydrocarbon (BHC) compounds are known to be emitted by plants, but only a few are emitted in relatively large quantities. The magnitude of BHC emissions from individual trees is affected by ambient light and temperature, species-specific emissions rates, and leafmass. Like other volatile organic compounds (VOC), BHC emissions react with oxides of nitrogen (NOx) to form ozone and, thus, can contribute to urban air pollution. On average, BHC emissions are as reactive or more reactive than the VOC emissions from automobiles and can have higher ozone-forming potential. An accurate estimate of the overall magnitude of BHC contributions is important in formulating strategies to reduce peak ozone concentrations because an effective strategy will take into account the relative strengths of NOx and VOC emissions. The choice between NOx and VOC controls is crucial since an incorrect emphasis may result in non-attainment of ozone-reduction goals and control measures for either NOx or VOC involve enormous costs. As part of a program to develop a reliable BHC emission inventory for the Central Valley of California, a quantitative investigation of the leafmass of urban trees was conducted. Twenty-one trees in Bakersfield, Calif., were harvested and leaves removed, dried, and weighed. Leaf masses per tree ranged from 1.5 to 89.6 kg. Leaf mass densities (dry leaf mass per area of crown projection) ranged from 150 to 3200 g·m-2, as much as eight times greater than leaf mass densities for deciduous forests and more than twice those for coniferous forests. These data suggest the BHC contributions of urban trees may be underestimated if their foliar masses are calculated using forest-based leaf mass density data.
). Outdoor air pollution is also known to trigger asthma symptoms in both children and adults ( Walling, 2002 ; Woodruff et al., 2003 ). Childhood asthma is the most common chronic disease in children, with increases in the number of cases occurring in
Indoor air pollution is ranked as one of the world's greatest public health risks ( Wolverton, 1997 ). The United Nations Development Program estimated in 1998 that over 2 million humans die each year due to the persistence of deleterious indoor air
physiologic problems such as blindness, bullheads, and bent neck is fascinating to read. Environmental imbalances, air pollution, and pesticide toxicity, nutritional deficiencies, and nutritional toxicities are the next interesting sections. Part III covers
/sustainable) and irrigating with non-potable water (sustainable) are included as options. Environmental issues are discussed in Chapter 6, including: nutrient and pesticide leaching and runoff; human health and wildlife concerns linked to pesticides; air pollution