Etiolated seedlings from Triticum aestivum L. (wheat), Zea mays L. (maize), Lens culinaris Medik. (lentil), Pisum sativum L. (pea), and Phaseolus vulgaris L. (bean) were studied during a four day period following transition into light. De-etiolation was expected to induce oxidative stress in seedlings, which would necessitate increased antioxidant enzymes. Triticum and Phaseolus seedlings were relatively quick to increase chlorophyll (chl) levels in light, whereas dark-germinated Zea, Lens, and Pisum seedlings had lower chlorophyll contents compared to light-germinated seedlings after four days of light exposure. The chl a/chl b ratio began significantly higher in light-germinated seedlings compared to dark-germinated seedlings. Chl a/chl b ratios were not significantly different between light- and dark-germinated treatments within two days of light exposure in Triticum and Phaseolus, but were still different in Zea, Lens, and Pisum after four days of light exposure. Leaf ascorbate peroxidase (APX) activities were higher in etiolated seedlings compared to light-germinated seedlings. By 3–4 days of light exposure, APX activities in dark-germinated seedlings had decreased to levels similar to light-germinated seedlings in most species. Leaf catalase activities were higher in light-germinated seedlings compared to dark-germinated seedlings. Following 4 days of light exposure, catalase activities in light-germinated seedlings remained higher than in dark-germinated seedlings. Thus, these species all respond similarly to oxidative stress during de-etiolation, but to different extents and at different rates. Moreover, different expressions of enzyme activities can take on different meanings, depending on the cellular location of the enzyme and the physiological changes occurring in that location.
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Vol. 113 • No. 3/4