Abstract: With field pot experiment, the effects of two dosages of enhanced UV-B radiation on the morphology, physiology, biomass allocation, and chemical composition of C₄ plant Amaranthus retroflexus were studied. The results indicated that under the effects of enhanced UV-B radiation, the branch number, leaf number, plant height, and stem diameter had less change, the plant CAT activity was significantly higher than that of the control (P<0.05), but the SOD activity was less affected. The POD activity was significantly higher than the control under low dosage UV-B radiation, but had less change under high dosage UV-B radiation. The MDA content increased with increasing UV-B radiation (P<0.05). Under low dosage UV-B radiation and at harvest, the biomass allocation in leaf increased significantly but that in root was in adverse; while under high dosage UV-B radiation, less change was observed in the allocation. UV-B radiation induced significant changes in the chemical composition of root, stem, and leaf. Under UV-B radiation, the soluble protein, lignin, and fat contents in leaf, lignin content in root, and cellulose and lignin contents in stem were increased, while the starch content in leaf and the soluble sugar, starch, and fat contents in stem were decreased significantly (P<0.05), compared with the control.

Key words: Larix chinensis population, Spatial distribution, Clustering pattern type, Scale