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  • Author or Editor: Kang Gao x
  • HortScience x
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In this study, five cultivars of cut chrysanthemum Chrysanthemum ×morifolium Ramat., ‘Jinba’, ‘Yuuka’, ‘Fenguiren’, ‘Xueshen’, and ‘Huangjin’ were used to explore the functions of 5-azacytidine (5-azaC) on chrysanthemum growth and flower development. The results showed that 5-azaC had different effects on the growth of the five cultivars during in vitro culture. The final statistics showed that low concentrations promoted plant growth, whereas high concentrations inhibited growth; however, each cultivar had different growth curves, demonstrating that 5-azaC had no consistent inhibitory actions on growth. On the basis of the squaring time and flowering time statistics, we found that 5-azaC had a certain effect on the flowering time of all cut chrysanthemums, and all of these cultivars showed extremely early strains. Summer chrysanthemum (‘Yuuka’, ‘Fenguiren’, ‘Xueshen’, and ‘Huangjin’) treatments led to both early and delayed flowering. When the statistics were analyzed for different individuals, we found that the treatments shortened the squaring time in early-flowering plants. In ‘Jinba’, an autumn chrysanthemum, the treatment helped broken juvenile limitations and allowed plants to undergo photoperiod induction in the early stage. Additionally, we also determined the flower diameter differences in these treatments; ray florets from ‘Yuuka’ and ‘Huangjin’ trended to show tubular florets, and the location of tubular and ray florets were changed in ‘Xueshen’ capitulum. In conclusion, on the basis of flowering time in five early varieties of cut chrysanthemum, we propose that 5-azaC may regulate the methylation level of genes that control flower induction and flower development. These results provide phenotypic data and material for exploring the function of DNA methylation in regulating flowering.

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The large-flowered Chinese chrysanthemum is one of the most morphologically complex ornamental plants, and its identification and classification requires a well-defined and reproducible system. The diversity of the capitulum is determined mainly by multiple shapes of ray florets. However, the existing classification systems for ray floret types are incomplete and unsystematic. In this study, 299 ray florets from 151 large-flowered chrysanthemum varieties in China, as well as 12 related traits of ray florets, were selected for quantitative classification. First, as one of the most important indices of ray floret shape, the corolla tube merged degree (CTMD) was defined as the corolla tube length/ray floret length (CTL/RFL). Combined with a probability grading method and linear regression analysis, the CTMD was divided into three groups, flat, spoon, and tubular, of which the CTL/RFL ranged from 0 to 0.20, 0.20 to 0.60, and 0.60 to 1.00, respectively. Second, Q-mode cluster analysis indicated that each group could be further categorized into three types (straight, curved, and atypical), based on other important variables in the ray floret. Finally, the ray floret was classified into nine types, including flat-straight, flat-curve, flat-atypical, spoon-straight, spoon-curve, spoon-atypical, tubular-straight, tubular-curve, and tubular-atypical. This ray floret classification system will be valuable in the classification of capitulum shape and has significance for the identification, breeding, and international standardization of chrysanthemum cultivars.

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Hydrogen sulfide (H2S) was recently recognized as an endogenous gaseous molecule involved in seed germination, root organogenesis, abiotic stress tolerance, guard cell movement, and delay of senescence in plants. In the present study, we show that H2S participates in the regulation of postharvest ripening and senescence in fresh-cut kiwifruit, Actinidia deliciosa. Fumigation of fresh-cut kiwifruit with the H2S donor sodium hydrosulfide (NaHS) solution prolonged kiwifruit storage time and alleviated senescence and tissue softening in a dose-dependent manner at an optimal concentration of 1.0 mmol·L−1 NaHS. H2S treatment maintained higher levels of reducing sugars, soluble proteins, free amino acids, ascorbate, and chlorophyll and lowered carotenoid levels. H2S treatment also significantly decreased the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (O2 ) during fruit storage compared with water controls. Furthermore, the activities of guaiacol peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were increased by H2S treatment, whereas the activity of lipoxygenase (LOX) was decreased compared with untreated controls. Taken together, these results suggest that H2S is involved in prolonging postharvest shelf life and plays an antioxidative role in fresh-cut kiwifruit.

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