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The growth of Dendrobium nobile is often stressed by zinc. To study the effect of zinc on the growth and biosynthesis of medicinal components, external zinc was regularly sprayed on Dendrobium nobile. The results showed that the net photosynthetic rate, transpiration rate, stomatal conductance, chlorophyll A and B of leaves increased first and then decreased with the increase of zinc concentration. At 400 µmol/L, they reached the maximum value, indicating that a certain dose of zinc could promote the photosynthesis of Dendrobium nobile. When the concentration of zinc was 400 µmol/L, which could promote the synthesis of SOD, the content of APX and AsA reach the maximum. The content of polysaccharide reached the maximum on the 7th day, the content of polyphenols reached the maximum on the 14th day. This result suggests that exogenous zinc can promote the accumulation of active components in Dendrobium nobile, and when the zinc concentration is 400 µmol/L, the promoting effect is greatest. While, it was found that the polysaccharide can combine with zinc well to form polysaccharide-zinc chelate, and transform inorganic zinc into organic zinc, which was stored in the form of polysaccharide-Zn in vivo and reduced the damage to Dendrobium nobile by Zn-stress Zinc affects physiology and biosynthesis of medicinal components inDendrobium nobile Lindl.

Plumbago indica L. is a perennial herb with ornamental and anticancer medicinal functions widely distributed in the tropics. It is affected by temperature and cannot bloom normally in colder subtropical regions, which seriously affects its ornamental value. To create low-temperature resistance mutants and enrich new germplasm resources, this study used tissue culture and chemical reagent (0.5 mmol/L NaN3) and low-temperature stress (0°C, full darkness for 48h) induction to target and screen for cold-resistance mutants. The results showed that the ISSR band polymorphism ratio of the 24 suspected mutant materials was 87.5%. The DNA profiles of the 9 mutants initially identified were altered. The content of plumbagin in the stems and leaves of the mutants was examined, and it was found that the accumulation in the leaves of the mutant SA24 could be as high as 3.84 times that of the control, which was 0.5991%. There were significant differences in the anatomical structures of roots, stems and leaves. The mutants mostly exhibited reduced root diameter (only 0.17-0.69 times that of CK), increased stem diameter (up to 2.19 times that of CK), enlarged mesophyll cells, increased thickness (up to 1.83 times that of CK) and high specificity, which are thought to be important for the different cold resistance obtained by the mutants. In the cold resistance experiment, four cold-tolerant mutants were successfully screened according to their morphological characteristics and physiological indexes, and the mutagenesis efficiency could be as high as 2.22% and did not affect the accumulation of plumbagin in their stems and leaves, even higher than CK. The responses of the screened mutants SA15, SA19, SA23 and SA24 to low temperature showed slower leaf wilting, higher light energy conversion efficiency, less accumulation of MDA content, increased enzymatic activities of antioxidant enzymes (SOD, CAT, POD) and more accumulation of soluble sugars and proline content. These characteristics are consistent with the response of cold-resistance plants to low temperatures. The cold- resistance mutants cultivated in soil were observed of agronomic and ornamental traits for one year, mainly manifested as delayed flowering and delayed entry into the senescence stage. This study provides a more rapid and accurate technique for identifying and screening cold-tolerant mutants, and lays the foundation for future experiments on the creation of new cold-resistant varieties.

Background Heteromorphic self-incompatibility (HetSI), which is regulated by gametophytes, occurs in some species as a strategy to promote cross-pollination. Studies on HetSI are rare, and there is little evidence to establish the mechanism of HetSI. This research aimed to reveal metabolic changes occurring in HetSI. We used fluorescence microscopy as a tool to compare growth behavior in self-incompatible (SI) and self-compatible (SC) pollination in both pin and thrum flowers of Plumbago auriculata and to identify the ideal timepoint for sample collection for subsequent experiments. We also employed environmental scanning electron microscopy (ESEM) to evaluate intermorph structural differences in the pollen grain and stigmas in relation to heteromorphic self-incompatibility. Importantly, UPLC-MS/MS was applied in this study to identify metabolites, compare metabolic differences between pin and thrum styles and monitor metabolic changes in styles and SC and SI pollinations in the two type of flowers. Results The metabolites mainly included amino acids, flavonoids, glycosides/sugars, phenols, other organic acids, fatty acids/lipids, amines and alcohols. Surprisingly, high-energy nutrients such as amino acids, flavonoids, phenols alcohols and tricarboxylic acid cycle-related metabolites were found at higher levels in SI pollinations than in SC pollinations. Conclusion This result indicates that physiological changes in pollen-stigma interactions are different in pin, thrum styles and SC, SI pollinations and that energy deficiency may not be one of the reasons for HetSI.