Early diagnosis of SO2-stress by volatile emissions in some crop plants

Abstract

Fumigation experiments with SO performed on the seedlings of three plant species viz, tomato (Lycopersicon esculentum), mung bean (Vigna radiata) and maize (Zea mays) resulted in the emission of volatiles. Acetaldehyde and ethanol were produced in the fumigated plants. In addition, there was also an increased production of ethylene and ethane. The production of these volatiles was positively correlated to the SO concentrations of 4.2 and 8.3 μmol m (0.1 and 0.2 ppm). Ethylene was emitted primarily from SO-stressed yet healthy leaves, whereas high ethane levels were detected in leaves with visible injury symptoms. However, with the appearance of visible injury symptoms, there was a decline in ethylene, acetaldehyde and ethanol emissions. Synthesis of ethylene and ethane seems to be a result of different metabolic pathways. Ethane evolution and its inhibition by antioxidants indicate SO-mediated lipid peroxidation by free radical species formed during sulphite oxidation. Perturbation in the cellular respiratory machinery results in the formation of acetaldehyde and ethanol. Since the rates of emissions of ethane, acetaldehyde and ethanol fromplant species were positively correlated to their relative resistance to SO, the production of these gases could be used as a reliable diagnostic tool for biomonitoring air pollution (SO) stress.

Ethanol in the stems of trees

“…While ethanol production per se is regulated by cytoplasmic pH (Roberts et al 1984a), ethanol production has only been associated with hypoxic tissues, acidic gas stress of leaves or severe necrosis (John and Greenway 1976, Davies 1980, Kimmerer and Kozlowski 1982, Barta 1984, Kimmerer and MacDonald 1987, MacDonald et al 1989, Thotnson et al 1989, Chauhan 1990). Both PDC and ADH are known to catalyze the production of compounds other than acetaldehyde and ethanol, respectively.…”