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Lu Zhang and Xiangyang Sun

Composting is considered an environmentally sound and economically viable alternative for the management of organic residues. Although compost product may be used as a peat substitute in soilless culture, it generally has poor physical structure, low nutrient content, high pH, and high salt content. This study chose the coir fiber (CF) produced from coconut (Cocos nucifera) and bamboo vinegar (BV) produced from mottled bamboo (Phyllostachys bambusoides) as the media amendments, and evaluated the effects of CF (at 0%, 15%, and 25%) and/or BV (at 0%, 0.5%, and 1.0%) on the physical, chemical, and microbiological properties of composted green waste (CGW) and on the growth of peacock arrowroot (Calathea makoyana). The highest quality growing medium and the best growth of peacock arrowroot were obtained when CGW was amended with the combination of 15% CF and 0.5% BV; the lowest quality medium and the least plant growth were obtained with nonamended CGW. The optimal combination not only improved particle-size distribution and adjusted bulk density (BD), porosity, and water-holding capacity (WHC) into ideal ranges, but it also decreased pH and electrical conductivity (EC) and increased microbial numbers, enzyme activities, and macro- and micronutrient contents in the CGW. Relative to the nonamended CGW, the optimal CGW reduced the BD from 0.58 g·cm−3 to 0.34 g·cm−3 and the pH from 8.05 to 5.61, and increased the total porosity (TPS) from 48.1% to 77.0% and the WHC from 57.4% to 75.5%; the optimal CGW increased shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, plant height, crown breadth, number of leaves, and total root length by 83.9%, 77.8%, 66.1%, 65.1%, 63.6%, 73.8%, 55.6%, and 65.2%, respectively.

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Jiuxing Lu, Weiru Yang and Qixiang Zhang

Control of development is an important issue in the production of ornamental plants. Gibberellins (GAs) play a key role in regulating plant growth and development. DELLA is nuclear negative regulators of GA signaling. We identified two DELLA homologous genes, PmDELLA1 and PmDELLA2, in the genome of mei (Prunus mume) genome. We analyzed the structure, expression patterns and molecular functions of both genes. Tissue expression analysis showed that both genes were transcriptionally active. PmDELLA1 showed higher expression in seeds than PmDELLA2. This indicated that PmDELLA2 plays different roles from PmDELLA1 in seed germination. The expressions of both genes at various flowering stages were relatively low. We speculated that PmDELLAs might be positive regulators of flowering by releasing the repression of GA during floral blooming. Transgenic arabidopsis (Arabidopsis thaliana) lines overexpressing the two genes showed dwarf and delayed flowering. We confirmed that the two PmDELLAs were partially conserved with genes encoding DELLA proteins in arabidopsis. Our bioinformatics and functional analyses provide information that may be valuable to improve the economic, agronomic and ecological properties of mei and other Rosaceae fruit trees.

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Na Zhang, Lu Han, Lixin Xu and Xunzhong Zhang

Ethephon [ETH (2-chloroethylphosphonic acid, an ethylene-releasing compound)] has been used as a plant growth regulator in turfgrass management. The aim of the study was to assess the effects of ETH seed treatment on drought tolerance of kentucky bluegrass (Poa pratensis) seedlings. Seeds of two kentucky bluegrass cultivars, Midnight and Nuglade, were exposed to ETH treatment or untreated as controls. Seedlings were then exposed to two water regimes: well-watered conditions and polyethylene glycol (PEG)–induced drought conditions. ETH-treated plants exhibited better turf performance relative to the untreated control under PEG-stressed conditions illustrated by higher relative water content (RWC) and lower lipid peroxidation and lower electrolyte leakage (EL). In both cultivars, ETH treatment increased enzyme activity of ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT); proline content; and soluble protein content under PEG-induced drought conditions. The results suggest that ETH seed treatment can improve drought tolerance in kentucky bluegrass seedlings.

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Da-Peng Zhang, Zi-Lian Zhang, Jia Chen and Jiang Lu

By using the micro-volume radio-ligand binding essay, the changes in the kinetic characteristics of the abscisic acid (ABA)-binding protein(s) of the Kyhoh grapevine (Vitis vinifera × V. labrusca) fruit during the different stages of fruit development have been studied. The changes in the berry volume growth, concentration of sugar, organic acids, and ABA in fruit mesocarp have been surveyed, especially for studies of ABA-binding protein. The dissociation constant (Kd) and ABA binding maximum (Bmax) were determined by the Scatchard plots for ABA binding in microsomes of the fruit. They are Kd = 17.5, 50.0, 6.3, 13.3 nmol·L–1; Bmax = 98.6, 523.0, 41.6, 85.4 μmol·mg–1 protein, respectively, for the fruit developmental phase I, II, veraison, and phase III. The Scatchard plots showed a rectilinear function for all of the developmental phases including veraison, which suggests the sole ABA-binding site of high affinity for ABA in the fruit microsomes, but this site could either be only one kind of the same protein or consist of more kinds of different proteins for different developmental stages. The binding affinity of ABA-binding protein(s) for ABA was shown to be higher at veraison time than during other developmental phases; this binding affinity increased nearly by 10 times from phase II to veraison, while the concentration (Bmax) of the ABA-binding protein(s) decreased to the minimum at veraison. The very low concentration of ABA at veraison may be able to trigger the onset of fruit ripening due to the increase of the binding affinity of ABA-binding protein(s) for ABA at this time. The possible functions of the ABA-binding protein(s) for fruit development during the different developmental stages were discussed, and it is suggested that the protein(s) detected could be the putative ABA receptor(s) or transporter(s) for the action of this plant hormone in grapevine.

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Da-Peng Zhang, Zi-Lian Zhang, Jia Chen and Jiang Lu

The abscisic acid (ABA) has a key role in the regulation of grapevine fruit ripening, but the cellular and molecular biological mechanism of the hormone action in the fruit ripening remains unknown. By means of differential centrifugation, microsomes were prepared from Kyoho grapevine (Vitis vinifera L. × V. Labrusca L.) berries, and using the microsomes, we have obtained evidence for the occurrence of specific ABA-binding sites on the membranes with the microvolume radio-ligand binding assay. The binding sites had saturability, high affinity, and low capacity. The results of trypsin and dithiothreitol treatments to the microsomes suggested that ABA binding sites had the properties of proteins that might have disulfide group located at or near the binding site. The binding maximum amount of ABA in the microsomes was at pH 6.0 and the activity of ABA binding proteins was higher at 25 than at 0°C (temperature). The amount of ABA bound reached 54% of the ABA binding maximum (Bmax) for 10 minutes of incubation and Bmax reached for 30 minutes. The dissociation constant (Ka) and Bmax of ABA binding proteins in the microsomes were 17.5 nmol/L and 98.4 fmol/mg protein, respectively.

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Lu Gan, Xunzhong Zhang, Silu Liu and Shuxia Yin

Turfgrass performance under drought stress is impeded by plant water deficit and oxidative damage, which might be improved by the external application of osmoprotectants. Creeping bentgrass (Agrostis stolonifera L.) is a valuable species for low-cut golf surfaces as a result of its high density and fine texture. However, weak tolerance to drought stress is a primary shortcoming. In this study, the effect of exogenous glycinebetaine (GB) pretreatment on mitigating the damage from drought stress in creeping bentgrass cultivar ‘T-1’ was evaluated. Pieces of creeping bentgrass sod were subjected to four treatments: 1) well-watered control, 2) well watered and sprayed with 100 mm GB, 3) drought stress, and 4) drought stress and sprayed with 100 mm GB. Drought stress resulted in a remarkable decrease in turf quality (TQ), relative water content (RWC), and chlorophyll content, with significant increases in superoxide anion content (O2 ), malondialdehyde (MDA) content, superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activity. In contrast, pretreatment with 100 mm GB decreased the O2 and MDA content in water-stressed plants, and increased turf quality, chlorophyll content, SOD, CAT, and POD activity. Meanwhile, the expression level of the psbA, SAMS4, CMO, and ACS1 genes in leaf samples collected during the drought-stress stage was elevated in GB pretreatment. Notably, SAMS4 gene expression in GB pretreatment was significantly greater than in the untreated GB groups subjected to water stress. These results suggested that GB could mitigate the adverse effect of water stress on creeping bentgrass. The amelioration related strongly to the maintenance of the antioxidant enzyme system, accumulated endogenous compatible metabolites, and the elevation of gene expression levels. These findings lead us to conclude that GB pretreatment could be used as an ameliorative agent for creeping bentgrass against the deleterious effects of water stress.

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Lu Zhang, Xiuming Hao, Yonggeng Li and Gaoming Jiang

Early production and high energy efficiency are important in greenhouse vegetable production in cold regions. A dynamic temperature integration strategy with low pre-night temperature (PNT) has been developed to reduce energy consumption and to improve early fruit yield and energy use efficiency. However, the application of this temperature control strategy is feasible only if there is no crop yield and quality loss. To determine the low PNT tolerance threshold and explore the mechanism of this temperature control strategy on plant growth and development, the effects of four PNT temperature integration treatments (PNT9, PNT11, PNT13, and PNT15, with an actual PNT of 9.4, 11.3, 13.3, and 15.1 °C, respectively) on greenhouse tomatoes (Solanum lycopersicum) were investigated. The PNT was applied at the beginning of the night for 3 h, whereas temperatures in other periods during a day (24 h) were adjusted accordingly to ensure the same 24-h average temperature (19.4 °C) for all PNT treatments. Four cultivars (Bigdena, Clarance, Quest, and Conchita), representing all three types (beefsteak, cluster, and cherry) of greenhouse tomatoes, were used in the study. The optimum PNT for fruit yield was 13.8 and 14.9 °C for ‘Bigdena’ and ‘Conchita’, respectively. Low PNT down to 11 °C did not compromise fruit yield and plant development in ‘Clarance’, and thus a PNT lower than 13 °C can be used for ‘Clarance’ if it does not have a negative effect on fruit quality. In ‘Bigdena’ and ‘Conchita’, the above-ground biomass increased with increasing PNT at the low range of PNT, peaked at ≈13 °C PNT (13.7 and 13 °C for ‘Bigdena’ and ‘Conchita’, respectively), then declined at high PNT. Leaf photosynthesis rates were increased by the highest PNT (PNT15), whereas respiration rates were reduced by the lowest PNT (PNT9). Therefore, PNT at ≈13 °C might have allowed for the proper balance between the high photosynthesis for photoassimilate generation and the low respiration for photoassimilate conservation and thus accumulated the highest photoassimilate and the highest fruit yield in ‘Bigdena’. Flower development rate in ‘Conchita’ decreased linearly with low PNT, which might have limited the response of its fruit yield to low PNT and raised the optimum PNT for fruit yield to 14.9 °C. Temperature integration with proper low PNT can be an effective climate control strategy for increasing early fruit yield and energy use efficiency in greenhouse tomato production.

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Gang Lu, Wenlei Jian, Jiajing Zhang, Yijing Zhou and Jiashu Cao

The effects of silicon nutrition on the resistance to stem blight caused by Phomopsis asparagi was assessed in two asparagus cultivars, UC157 and Gynlim, and the activation of defense responses in inoculated plants was measured in a greenhouse with nutrient solution culture. The supply of silicon (Si) significantly suppressed stem blight development in inoculated plants. The disease index was significantly reduced in Si-supplied plants compared with Si-deprived plants in both cultivars. Supplement with Si enhanced Si accumulation in asparagus root and shoot. Si content was significantly higher in Si-treated plants when compared with control plants, but it was not significantly different between the two cultivars. Interestingly, inoculation with P. asparagi increased Si content in shoots in the cultivar UC157. Root-applied Si significantly enhanced the activities of pathogenesis-related proteins (PRs) such as catalase, peroxidase, polyphenoloxidase, and β-1, 3-glucanase in inoculated plants. However, Si treatment mostly failed to change significantly the activity of PRs in plants without fungal attack. So continuous feeding of Si to the plant is probably important for enhancing the resistance to infection by P. asparagi in asparagus.

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Junhuo Cai, Junjun Fan, Xuying Wei and Lu Zhang

Lycoris radiata has beautiful bright-red flowers with both medicinal and ornamental value. However, the mechanisms underlying an unusual characteristic of Lycoris radiata, flowering without leaves, remain unclear. In this study, climatic influences, biomass composition, and yearly variations in bulb contents across eight developmental stages of L. radiata were analyzed. Thus, L. radiata summer dormancy was investigated in three dimensions: climate-associated phenology, biomass distribution characteristics, and physiologic bulb changes. The results showed that dormancy was most strongly affected by high ambient temperature, followed by scape development, flowering, leafing out, vigorous leaf growth, flower bud differentiation, flower bud predifferentiation, and leaf maturation. Biomass allocation, bulb contents, oxidoreductase activity, and root activity fluctuated significantly in L. radiata among developmental stages. Relative bulb dry weight was greatest during the dormant period (95.95% of total dry weight) and lowest during vigorous leaf growth (November–December). Root biomass was also significantly greater during dormancy than during flowering, leaf maturation, and flower bud differentiation. Only root biomass during vigorous leaf growth was greater than root biomass during dormancy. However, in dormant bulbs, soluble sugar content, soluble protein content, root activity, superoxide dismutase (SOD) activity, and peroxidase (POD) activity decreased. Thus, summer dormancy in L. radiata only constitutes a morphologic dormancy of the aboveground plant; the bulb and root remain physiologically active. The results suggest that L. radiata is sensitive to both ambient temperature and light, and that summer dormancy is triggered by the synergistic stimulation of these two factors. Although temperature controls dormancy, it plays only a limited regulatory role during the L. radiata flowering period. Thus, it is difficult to induce flowering or regulate annual flowering in this species through temperature control alone.

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Lu Zhang, You-biao Hu, Hua-sen Wang, Sheng-jun Feng and Yu-ting Zhang

Plant growth and development are determined by complex exogenous and endogenous cues. A plant follows several temporally distinct developmental stages, including embryonic, vegetative, and reproductive. The vegetative stage, which is usually the longest stage, can be subdivided into juvenile and adult phases. The transition from the juvenile to the adult phase, also called the vegetative phase change, is characterized by anatomical, morphological, and physiological changes in the vegetative parts of the shoot. Recent studies in several systems have identified the genetic temporal mechanisms of this process, which is regulated by an endogenous age cue (i.e., microRNA156/157) and its targeted genes (i.e., Squamosa promoter binding protein-box transcription factors). This review summarizes the recent advances in the study of the underlying regulatory mechanisms of vegetative phase change. This review also describes the modes of miRNA action and the functions of their targeted genes in this highly conserved developmental process.