Evaluating the effects of UV-B and UV-A irradiances on plant pigments, photosynthesis and growth in Glycine max L
Increasing penetration of UV-B radiation to the earth's surface resulting from stratospheric ozone depletion is an important environmental concern, but plant response to UV-B irradiation has been difficult to assess. The UV-A irradiance has not been specifically measured or controlled previously. The experimental UV-A was controlled in a series of three glasshouse experiments conducted under high photosynthetic photon flux (midday PPF [ge] 1200 [mu]mol m[sup [minus]2] s[sup [minus]1]). Low (LT) and High (HT) daily UV-B[sub BE] irradiances (10.7; 14.1 kJ m[sup [minus]2]) were utilized in two experiments, whereas treatments with different UV-B[sub BE]:UV-A ratios (< 0.5, for total UV-A) were examined in the third. UV-B and UV-A irradiation effects were determined for pigment, photosynthesis, and growth variables in 3 isolines o f two soybean cultivars, Clark and Harosoy. UV-B irradiation consistently induced UV-B absorbing compound and photosynthetic pigment accumulation, especially carotenoids, and increase in the Chl-a/b ratio, and a stomatal limitation to photosynthesis. UV-B absorbing compounds were correlated with total carotenoids (UV-B irradiated plants) and with biomass (all plants). Many variables exhibited an interaction between spectral quality and quantity, interpreted as moderation of UV-B irradiation resembled [open quotes]shade[close quotes] responses, the involvement of phytochrome was suggested, and the interaction was explained as the net response induced by phytochrome and the UV-A/Blue photoreceptor. LT responses often were greater than those for HT, and differences in responses for the LT and its UV-A Control were often more clearly separable, providing an explanation for the common failure to verify a dose-related response in UV-B studies. This was further supported by response of pigments to three treatments with different UV-B[sub BE]:UV-A ratios.
- Research Organization:
- Maryland Univ., College Park, MD (United States)
- OSTI ID:
- 5425159
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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560140* - Radiation Effects on Plants