| Using the young seedlings of wild type (WT) and four mutants (phyA, phyB, phyAphyB and hy4) of Arabidopsis thaliana as plant materials, the effects of light quality and kinetin (KT) on some photomorphogenesis responses such as cotyledon enlargement, hypocotyl growth inhibition, accumulation of chlorophyll and anthocyanin were investigated in the present study. Photoreceptor functions and interaction of light and KT in the responses was examined and discussed. The main results are as follows:1 Effects of Light quality and KT on cotyledon enlargement5-d-old seedlings of Arabidopsis wild type and mutants were harvested and the cotyledons were cut to use as excised cotyledon or the whole seedlings were used as intact cotyledon. Excised and intact cotyledons were incubated in the medium (pH 6.0) with or without KT under white light (WL), red light (RL), far-red light (FR) and UV-B at 21?癈 for some periods of time before cotyledon area were determined by a DELTA-T area measurement system. It was found that both excised and intact cotyledon enlarged apparently under light especially WL, BL and RL. FR had a smaller effect on enlargement and a reduced cotyledon area was observed after UV-B irradiation. By the analysis of mutant growth we can conclude that the photoreceptors of phyA, phyB and cryl are responsible for the cotyledon enlargement under FR, RL and BL, respectively. It was proposed that a coaction might exist among phytochrome and cryptochrome in the regulation of cotyledon enlargement.KT induced a slightly increase of cotyledon area in darkness and apparent enlargement was obtained under light especially WL, BL and RL. Either light or KT could induced cotyledon enlargement and they showed independent and additive effect on the response.2 Effects of light quality and KT on hypocotyl elongationThe hypocotyl elongation of 2-d-old etiolated seedlings was inhibited evidently under continuous light including UV-B, WL, BL, FR and RL. The inhibition effectiveness was UV-B>WL>BL>FR>RL. The response was essentially controlled by phytochrome B in red light, phytochrome A in far red light and cryptochrome 1 in blue light. The coaction was also existed among different photoreceptors by analyzing mutants.In darkness, KT showed a similar inhibition of hypocotyl elongation as under WL. When the seedling grew in the light, the hypocotyl inhibition induced by KT was decreased. Inversely, when KT was present in the medium the light induced inhibition was also decreased. It is an independent process of light and KT on inhibition of hypocotyl elongation and they showed multiplication effect on the process.3 Effect of light quality on chlorophyll accumulation2-d-old seedlings grown under WL irradiated by WL, RL, FR, BL and UV-B irradiated for 3 d before the detection of chlorophyll content, it was showed that light quality influenced chlorophyll accumulation. Among different light qualities WL was the most effective. The order of the effectiveness is WL>RL>BL>UV-B>FR. The ratio of Ca/Cb, in the seedling was also influenced by light quality. Phytochrome A and phytochrome B were the main photoreceptors involved in regulation of chlorophyll accumulation and the ratio of Ca/Cb. A remarkable decrease of the Ca/Cb ratio was observed under FR grown seedlings especially phyAphyB seedlings.4 Effects of light quality and KT on anthocyanin accumulation2-d-old WL grown seedlings were irradiated with continuous WL, RL, FR, BL and UV-B, respectively, for 3 d and the accumulation of anthocyanin was detected. The results showed that light, especially BL and UV-B strongly induced the anthocyanin accumulation. RL was less effective in anthocyanin induction. By measuring the anthocyanin accumulation of the mutants, it was showed that phytochrome and cryptochromel were involved in the induction process.KT enhanced the accumulation of anthocyanin under blue light and had a concentration effects. The higher fluence rate of BL applied the stronger the induction of anthocyanin was observed under the same KT concentration...
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