CO_2 concentration may interact with photoreceptors to alter seedling elongation under the litter layer
LE3 .A278 2008
Master of Science
To explore the physiological mechanisms by which CO2 and light interact to control seedling elongation, 'Sinapis' and photoreceptor mutants of 'Arabidopsis' ('phyA, phyB, phyA&B, cry1, cry2, crv1&2', and 'zeaxanthin'), and their corresponding wild-types (ler-0, ler-2, and col) were grown under continuous darkness, red or blue light, and in ambient or elevated CO2. The zeaxanthin mutant exhibited altered hypocotyl inhibition in both light and darkness, but there was no difference in its response to elevated CO2 from its wild-type. Neither 'Arabidopsis' nor 'Sinapis' responded to elevated CO2 in blue light, but there was a response to CO2 by 'Sinapis' and the 'Arabidopsis ' wild-types in darkness and red light. In red light, 'phyA, cry1, cry2', and 'cry1&2' did not exhibit hypocotyl elongation in response to elevated CO2, implying points of interaction between CO2 concentration and the photoreceptors. The physiological mechanism for how this occurs is uncertain. To understand the ecological context for this interaction, a field study measured quantity and quality of light filtered through the litter layer of several different communities, and through dead versus live leaves from individual species. The CO2 concentration beneath the litter from these same sites was also sampled. In general, dead leaves transmitted more red and less far-red light than live leaves. Percent transmittance through leaf-litter was reduced significantly, while R:FR remained high. The elevated levels of CO2 found in the litter may alter seedling growth to stimulate seedling elongation despite a relatively high R:FR ratio.
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