Ginger (Zingiber officinale Rosc.) plantlets were propagated in vitro and acclimated under different photosynthetic photon flux densities (60 and 250 μmol m -2 s -1 = LI and HI, respectively). Increases in chlorophyll (Chl) content and Chl a/b ratio were found under both irradiances. In vitro plantlets (day 0) exhibited a low photosynthesis, but chloroplasts from in vitro leaves contained well developed grana and osmiophillic globules. Photoinhibition in leaves formed in vitro was characterized by decrease of photochemical efficiency and quantum efficiency of photosystem 2 photochemistry in HI treatment during acclimation. The new leaves formed during acclimation in both treatments showed a higher photosynthetic capacity than the leaves formed in vitro. Also activities of antioxidant enzymes of micropropagated ginger plantlets changed during acclimation.Additional key words: antioxidative enzymes; chlorophyll content and fluorescence; chloroplast ultrastructure; ginger; dry mass; net photosynthetic rate; photochemical quenching; plant height.
Ginger (Zingiber officinale Rosc.) somatic hybridization was attempted by using polyethylene glycol (PEG)-mediated protoplast fusion. Protoplasts of three ginger cultivars isolated from the embryogenic cell suspensions were fused with each other. The highest binary fusion rate [13.5% in the fusion of ginger 'Lushan Zhangliang jiang' ? 'Chenggu Huang Jiang' (LZ ? CH)] was observed with the treatment of 30% PEG6000 for 15 min. The three fusion combinations can efficiently develop into micro-colonies and redifferentiate, but only the fusion of ginger 'Chenggu Huang Jiang' ? 'Sichuan Zhugen Jiang' (CH ? SZ) could regenerate plantlets. Approximately 15 months were used for the regeneration of whole plants, and 15 shoots were obtained from the fusion of LZ ? CH. Three plantlets were identified as hybrids by using RAPD, and they were all diploids by analysis with flow cytometry.
IntroductionHigh salinity significantly hampers global agricultural productivity. Plants typically undergo lower nitrogen utilization efficiency (NUE) under salt stress. As an active byproduct from brassinolide biosynthesis, 24-epibrassinolide (EBR) is involved in regulating the stress-treated plant N absorption and assimilation. However, the exogenous EBR application effects’ on N absorption and assimilation in apple exposed to the salt-stressed condition remains unclear.MethodsWe sprayed exogenous EBR (0.2 mg L−1) on apple dwarf rootstock (M9T337) seedlings (growing hydroponically) under salt (NaCl) stress in a growth chamber. We analyzed the seedling development, photosynthesis and its-mediated C fixation, N (NO3−) absorption and assimilation in reponse to exogenous EBR application under salt stress.ResultsThe findings demonstrated that NaCl stress greatly hampered seedlings’ root growth and that exogenous EBR application obviously alleviated this growth suppression. Exogenous EBR-treated plants under NaCl stress displayed the more ideal root morphology and root activity, stronger salt stress tolerance and photosynthetic capacity as well as higher C- and N-assimilation enzyme activities, NO3− ion flow rate and nitrate transporter gene expression level than did untreated plants. Furthermore, the results of isotope labeling noted that exogenous EBR application also enhanced 13C-photoassimilate transport from leaves to roots and 15NO3− transport from roots to leaves under NaCl stress.ConclusionOur findings imply that exogenous EBR application, through strengthening photosynthesis, C- and N-assimilation enzyme activities, nitrate absorption and transport as well as synchronized optimizing the distribution of seedlings’ C and N, has a fundamental role in improving NUE in apple rootstock seedlings under salt stress.
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