Effects of SO₂ and O₃ on Allocation of ¹⁴C-Labeled Photosynthate in Phaseolus vulgaris

Abstract

There is good evidence that air pollutants may exert significant impacts on plant productivity by altering the partitioning of dry matter between plant parts (10,19,24,25). In addition to altered partitioning of carbohydrates between plant parts, the costs of repair from air pollution as well as disease-related stress may reduce carbohydrates available for growth by increasing the costs of repair of damage to cellular or metabolic systems (11). Studies with several plant species have indicated that the internal costs of maintaining leaf functions are high (11). These maintenance costs would be expected to be enhanced by exposure to pollutants and associated metabolic or cytologic injury.Several recent studies under both laboratory (8, 18, 22, 24) and field (14, 15) conditions have indicated that the processes of carbohydrate translocation may be both susceptible to exposure to air pollutants and useful as general indicators of pollutionrelated stress.In general, translocation has been reduced by exposure to air pollutants, however, with very low SO2 concentrations (0.08 ,ul I-') Milchunas et al. (15)

Seasonal changes in root and soil respiration of ozone‐exposed ponderosa pine (Pinus ponderosa) grown in different substrates

“…Several studies have reported decreases in root biomass associated with above-ground exposure to O., with concomitant decreases in root:shoot ratios (Cooley & Manning, 1987;Miller, 1987). These studies, along with C-partitioning studies (mostly on annual species) suggest that the proportion of C allocated to the root system is decreased in O.;-exposed plants (McCool & Menge, 1983;McLaughlin & McConathy, 1983;Gorrisen et al, 1991a). The mechanisms regulating assimilate partitioning in the whole plant are poorly understood (Wardlaw, 1990;GifTord et al, 1984), and although it is recognized that source-sink relationships change with developmental stage (Evans, 1991), assimilate partitioning is also influenced by both endogenous and environmental factors (Patrick, 1988).…”

The effect of long‐term ozone fumigation on the growth, physiology and frost sensitivity of Calluna vulgaris

“…McLaughlin et al (1982) demonstrated that a higher proportion of photosynthate remained in the foliage and branches of white pine following exposure to ozone, and less was exported to the bole and the roots. McLaughlin & McConathy (1983) proposed that ozone might cause a malfunction in the phloemloading process, increasing the allocation of photosynthetically fixed carbon to repair damage at source. Hanson & Stewart (1970) were able to show that ozone could delay starch hydrolysis and stimulate respiration which down-regulated photosynthesis.…”

“…Exposure to ozone might reduce photosynthesis (Reich & Amundson, 1985;Dann & Pell, 1989;Edwards, Wullschleger & Kelly, 1994) and yield (Heck et al, 1983), and alter carbon allocation (Cooley & Manning, 1987;Letchworth & Blum, 1977;McLaughlin et al 1982;McLaughlin & McConathy, 1983) in higher plants. However, most research to date on the plant physiological responses to ozone has focused on economically important fastgrowing crops and on forestry species.…”

Development of lines of radish differing in resistance to O3 and SO2

“…()., and SOj are both ktiowti to reduce root/shoot ratios (Tingey, Heck & Reinert, 1971 ;Okano et al, 1984;Godzik, Ashmore & Bell, 1985), with O., having larger effects on this parameter (McLaughlin & McConathy, 1983). This is mediated through the leaf, as O., does not directly affect below ground parts of the plant (Blum & Tingey, 1977).…”