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  • Author or Editor: Hongmei Qian x
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Two cultivars of Freesia hybrida, ‘Shangnong Jinhuanghou’ and ‘Shangnong Hongtaige’, were used to study the respiration rate and physiological responses during flower development and senescence. Phenotypically, the vase life of ‘Shangnong Hongtaige’ was significantly shorter than that of ‘Shangnong Jinhuanghou’. At the whole flower level, both cultivars displayed similar change patterns on respiration rate. However, the change patterns in tepals, stamens, and pistils showed some differences in the two cultivars. A respiratory climacteric existed in most organs in both cultivars except for the stamen of ‘Shangnong Jinhuanghou’. During flower development and senescence, the levels of soluble proteins and soluble sugars were very high at early stages, followed by a dramatic decrease, and the lowest levels occurred in wilted tepals in both cultivars. Superoxide dismutase (SOD) activities increased slightly at early developmental stages followed by a constant decrease in two cultivars, and SOD activities in ‘Shangnong Jinhuanghou’ were significantly higher than those in ‘Shangnong Hongtaige’. Peroxidase activities showed a constant increase before tepals started wilting followed by a decrease in wilted tepals in both cultivars. In both cultivars, electrolytic leakage and malondialdehyde (MDA) content in tepals increased with the progression of development and senescence. MDA content in ‘Shangnong Hongtaige’ was much higher than that in ‘Shangnong Jinhuanghou’. These results indicated that the respiratory climacteric, the decrease of antioxidant enzyme activities, the peroxidation of membrane lipid, and the loss of soluble compounds could be considered as indicators of flower senescence in Freesia.

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To study and model changes in the development of pak choi (Brassica rapa ssp. chinensis Makino), three pak choi cultivars—Xinxiaqing No. 5 (Xinxiaqing 5), Haiqing, and Huawang—were grown in a modern greenhouse. Four structural parameters, including leaf length, leaf width, and plant height and width, were measured regularly every 3 days. The results showed that the changes in plant height and width, and leaf length and width of the three cultivars followed sigmoidal trends. Logistical regression models {Y = K/[1 + (KL 0)/L 0 × exp(–r × t)]; Y = K/[1 + (KL 0)/L 0 × exp(−r × rad)]} of the leaf length and width accumulated with growth days and with accumulated radiation fit the actual data very well, with the correlation coefficient R 2 all greater than 0.98. The R 2 values of the plant width accumulation models were all greater than 0.93, whereas the R 2 values of the plant height regression models were not robust. In this study, the regression models of changes in plant height and width, and leaf length and width of pak choi were used to study the changes of morphological characteristics and analyze the change rules of pak choi growth and development.

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