Author
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Krizek, Donald |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 6/26/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: The role of photosynthetically active radiation (PAR) in modifying plant sensitivity and photomorphogenic responses to UV-B radiation has been examined by a number of investigators, but few studies have been conducted on UV-A, UV-B, and PAR interactions. The ratio of PAR/UV-B and UV-A/UV-B is important in influencing plant response to UV-B. Plant growth chamber and greenhouse studies conducted at low PAR, low UV-A, and high UV-B often show exaggerated UV-B damage. In general, one observes a reduction in total biomass and plant height and a shift in biomass allocation pattern with decreasing PAR and increasing UV-B. High PAR has been shown to ameliorate UV-B damage in many plants. There is some evidence that the primary damaging effect of UV-B is not on photosystem II reaction centers but on some component of the Calvin cycle, and that high PAR protection is conferred by this component rather than by the activity of UV repair enzymes (photolyase). The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and flavonoid concentration, known to be important in UV-screening. The quality of PAR is also important, particularly with respect to blue light which, together with UV-A radiation, plays a key role in photoreactivation. Native species appear to be more resistant to elevated UV-B than crop plants in terms of changes in biomass reduction, but both groups may show subtle changes in shoot elongation and leaf size. These morphological changes may have important consequences for natural ecosystems by altering the competitive balance in mixed communities. |
