Search Results
This study described a simple and quick method to detect trace quantities of a non-reducing sugar (viz. sucrose) in the root exudates of cucumber (Cucumis sativus) under CO2 enrichment. Sucrose was determined by analyzing fructose and glucose before and after invertase digestion using high-performance liquid chromatography. Using this technique, the optimal hydrolysis condition was 5.00 μg·mL−1 invertase for 10 minutes. The detection limit of ultraviolet-visible detector by post-column derivatization with tetrazolium was 0.25, 0.43, 0.48, and 1.95 μg·mL−1 for fructose, glucose, sucrose, and maltose, respectively, and sensitive enough for determination of sugars in root exudates. The dry weight of cucumber at the seedling stage (19 days after transplant) increased by 58.4% when the CO2 level was elevated from 380 to 1200 μmol·mol−1, whereas the differences were not significant at the initial fruiting stage (63 days after transplant). The photosynthesis rate in 1200 μmol·mol−1 CO2 was 58.0% higher than that in 380 μmol·mol−1 CO2 at the seedling stage and 74.2% higher at the initial fruiting stage. Total amount of sugars in cucumber root exudates was significantly increased with increasing CO2 concentration. The total sugars in root exudates increased by 130.4% and 102.3% in 1200 μmol·mol−1 CO2 compared with that in 380 μmol·mol−1 CO2 at seedling and initial fruiting stages, respectively. Elevated CO2 altered sugar composition in root exudates. Sugars in root exudates released per plant were significantly higher at the initial fruiting stage than that at the seedling stage, whereas the differences in sugars released per gram of root tissue between these two growth stages were not significant. Our results suggest that sugars were increased only in as much as root mass increased. This study provides a simple and quick method to detect 1 to 500 μg·mL−1 sugars in root exudates, and the results illustrate the variation in the sugar composition in cucumber root exudates among the CO2 levels and growth stages.
The investigation of hybridization processes and embryogenesis of heterozygote is an effective approach for early hybrids’ identification, which could provide reliable information for successful crossbreeding. In this study, we reported the whole hybridization processes of the direct cross and reciprocal cross between Michelia yunnanensis Franch. ex Finet et Gagnep. and Michelia crassipes Law using fluorescence microscopy after aniline blue staining, with the pollen germination on stigmas, pollen tube growth in styles, and subsequent extension into the embryo sac as well as the double fertilization processes are documented in detail. The M. yunnanensis × M. crassipes combination displayed considerable cross-compatibility, and the heterozygote embryogenesis was further observed with an approach of modified cryosectioning technique. Besides, the whole formation processes of hybrid seeds from artificial pollination to maturation were successfully observed. However, in the reciprocal cross, we found incompatibility between pollen grains of M. yunnanensis and stigmas of M. crassipes for the reason of hysteretic identification, as well as the abnormal callose deposition which belongs to the prefertilization barriers. This is the first study in which the complete and clear hybridization processes in Michelia were reported. We inferred that unilateral incompatibility of M. crassipes detected in this study may also exist in some other Michelia species. In artificial hybridization practices, we suggest some special treatments for overcoming prefertilization barrier should be taken when treating M. crassipes as the maternal parent.
NAC transcription factors have been characterized in numerous plants, and the NAC gene has been shown to be involved not only in plant growth and development, but also in plant responses to abiotic and biological stresses, such as drought, high salinity, low temperature, and anaerobic/hypoxic stress. Creating an environment of anaerobic/hypoxic stress has been shown to be one of the effective storage methods for delaying the browning of fresh-cut lotus (Nelumbo nucifera) root. However, whether NAC is associated with lotus root browning under anaerobic stress has not been studied. In this study, vacuum packaging (VP; anaerobic/hypoxic stress) effectively delayed the browning of fresh-cut lotus root. The changes in the expressions of NnPAL1, NnPPOA, and NnPOD2/3 were consistent with phenylalanine aminolase, polyphenol oxidase (PPO), and peroxidase (POD) enzyme activity changes and lotus root browning. Using RNA sequencing, five NnNAC genes were isolated and studied. Transcriptional analysis indicates that the NnNAC genes showed different responses to VP. The expressions of NnNAC1/4 were inhibited by VP, which was consistent with the observed change in the degree of fresh-cut lotus root browning. However, NnNAC2 messenger RNA (mRNA) levels were upregulated, and the expressions of NnNAC3/5 showed no clear differences under different packaging scenarios. Thus, NnNAC1/4 were identified as promising candidates for further transcriptional regulation analysis in lotus root to understand more fully the molecular mechanism of browning under anaerobic/anoxic stress.
Ethylene response factor (ERF) genes have been characterized in numerous plants, where they are associated with responses to biotic and abiotic stress. Modified atmosphere packaging (MAP) is an effective treatment to prevent lotus root browning. However, the possible relationship between ERF transcription factors and lotus root browning under MAP remains unexplored. In this study, the effects of phenol, phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) enzyme activities; and PPO, PAL, POD, and ERF gene expression on fresh-cut lotus root browning were studied with MAP. The expression pattern of ERF2/5 correlated highly with the degree of browning. It is suggested that NnERF2/5 can be used as an important candidate gene for the regulation of fresh-cut lotus root browning under MAP, and the correlation of each gene should be studied further.
Ethylene response factor (ERF) genes have been involved in responses to biotic and abiotic stress, including hypoxia and anaerobic stress. Vacuum packaging (a typical anaerobic stress) is an effective storage method used to delay browning of fresh-cut lotus root (Nelumbo nucifera). In model plants, ERF genes have been identified as responsive to hypoxia. Whether ERF is associated with browning of vacuum-packaged lotus root has not been studied. The effects of vacuum packaging on browning, phenolic content, the enzyme activity of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD), and PPO, PAL, POD, and ERF genes expression in fresh-cut lotus root were studied. Downregulation of NnPAL1, NnPPOA, and NnPOD2/3 attributable to vacuum packaging coincided with increased related enzyme activities and the degree of browning of fresh-cut lotus root. The expression patterns of NnERF4/5 were consistent with the changes in NnPAL1, NnPPOA, and NnPOD2/3 gene expression. It has been proposed that NnERF4/5 could have be important regulators of fresh-cut lotus root browning, and that the relationships of NnERF4/5 and NnPAL1, NnPPOA, and NnPOD2/3 should to be studied further.