Foliar Fatty Acids and Sterols of Soybean Field Fumigated with SO₂

Abstract

Sixty-day-old soybean plants were exposed in the field to 78.7 parts per one-hundred million of SO2 in an open-air fumigation system for 20 days. Leaves from the top one-fourth and bottom one-fourth of the plants were analyzed for chlorophyll, free fatty acids, fatty acid esters, polar lipid fatty acids, and sterols. Fumigated plants had a lower chlorophyll, free fatty acid, and polar lipid content, but a higher fatty acid ester content. Of the individual fatty acids, linoleic and linolenic acid increased with SO2 fumigation while palmitic acid decreased. SO2 fumigations had only a minor effect on leaf sterols. In general, the lower, more mature leaves showed a greater response to SO2 exposure.Sulfur dioxide is a gaseous discharge from industry and power plants, and, at times, its concentration in the ambient air can be high enough to produce phytotoxic effects (13,21). At a high enough concentration, SO2 causes a water-soaking appearance, as well as interveinal chlorosis, in leaves. At the cellular level, SO2 affects a number of events, e.g. transpiration, respiration, and photosynthesis (13, 21). The exact sequence of events is unclear, but SO2 does interfere with the structure and permeability of cellular membranes, and it has been suggested that SO2 affects the lipid component of membranes (11,14). However, studies to demonstrate the SO2 effect on lipid metabolism are few.Treatment of pine (Pinus banksiana Lamb) needles with aqueous SO2 solution produced a marked reduction in glycolipids (11), and studies with radioactive acetate have shown that both aqueous and gaseous SO2 inhibit lipid biosynthesis (14). The effect of SO2 was greater in young or developing needles than it was in fully developed needles. In American elm (Ulmus americana L.), the decrease in lipids with SO2 treatment was much less pronounced and depended largely upon the physiological age of the plant (2). Like those of pine, the younger elm leaves showed a greater response. Fumigation with gaseous SO2 demonstrated that pollutant concentration and length of exposure determine the extent of inhibition in lipid biosynthesis (14). In pine, lipid biosynthesis was partially or completely recovered within 2 days after removal of the pollutant (14); in elm, the effect was more lasting, up to 5 weeks in young leaves (2).The

Fatty acids of soybean seeds harvested from plants exposed to air pollutants

“…The results obtained in the present investigation are surprising, since a general decrease in foliar lipids had been observed with S02 exposure in long-term field (Grunwald, 1981) and greenhouse studies (Constantinidou and Kozlowski, 1979). In addition, an inhibition in the incorporation of radioactive acetate into foliar lipids in short-term experiments with S02 had also been demonstrated (Khan and Malhotra, 1977;Malhotra and Khan, 1978).…”

“…was acidified (pH 2-3) and again extracted 3X with hexane to remove the free fatty acids. The remaining acidic alcohol fraction, to which a known quantity of heptadecanoic was added, contained the polar lipids, mainly phospho-and glycolipids (Grunwald, 1981). The total fatty acid, neutral ester, and polar lipid fractions were saponified in 5% KOH in 95% aqueous methanol (w/v) for 30 min.…”

Photosynthetic Capacity, Stomatal Behavior and Chloroplast Ultrastructure in Leaves of the Endangered Plant Carpinus putoensis W.C.Cheng during Gaseous NO2 Exposure and after Recovery

“…These changes may be caused, in part, by NO 2 altering the semipermeable properties of the plastid envelope. After entering the leaf through the stomata, NO 2 , a kind of acidic pollutant, could be converted into NO 2 − , by acidification [48]. However, we did not investigate NO 2 − accumulation in the exposed leaves, so the relationships between increased Chl content, the Fv/Fm ratio, and NO 2 − accumulation remain unclear.…”

Metabolic engineering of soybean affords improved phytosterol seed traits

“…In plants, phytosterols are present in amounts varying from approximately 0.01%–0.1% wet weight, which translates to 100–1000 mg of total sterol in a kilogram of fresh weight material (Nes, 1977). Soybean leaves synthesize sterols, mostly Δ 5 ‐phytosterols (Grunwald, 1981). Yet, in mature soybean seeds, approximately 35% of the total sterols are present as intermediates (Nes, 1990; Marshall et al.…”