though relatively low
may be sufficient to cause significant effects on plants. Ethylene is a natural maturation hormone in plants
controlling ripening and aging of fruits. Effects of ambient levels of C2H4 on plants growing in the urban environment are potentially great
as C2H4 has significant biological activity at very low concentrations (e.g.
ppbv). One of the best-documented effects of C2H4 exposure is dry sepal of orchids
associated with use of C2H4 illuminating gas in greenhouses. Dry sepal has also been reported in urban areas
presumably from elevated levels of C2H4 associated with automobile emissions. Other plants in the flowering stage may be sensitive to C2H4 exposures. Common C2H4-induced responses include premature bud break
inhibition of flowering
and accelerated flower aging. Because of its hormonal properties
C2H4 has the potential to cause widespread adverse effects on plants. However
field identification of injury resulting from such exposure may be nearly impossible
as injury mimics natural senescence and changes induced by a variety of environmental factors. An interesting example of this problem is the widely observed premature pigmentation of tree and shrub leaves along many major highways. Air quality 202
Menu
