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Plant growth and development relies on light and is influenced by light. Light-emitting diode (LED) technology is nowadays providing the possibility for regulating plant growth and development by modifying light spectral composition. Many researches have been carried out to figure out the effects of light quality on various aspects of plant behaviors, including plant morphology, physiology, and biochemistry. In this review, we summarized those research outputs, in order to give suggestion of light quality application for both research and production purposes, in the field of productional yield, productional quality for horticultural plants including vegetables or ornamentals in difference with cultivation goals.

In this study, Dianthus caryophyllus L. was used as the experimental plant to investigate the effects of rooting substrate and exogenous auxin concentration on the adventitious rooting of the stem cuttings. Our results showed that the formulated substrates with different physicochemical properties significantly affected the root formation. The substrate with a ratio of cocopeat to perlite at 1:1 (v:v) resulted in the optimum rooting of D. caryophyllus cuttings. Different Indole-3-butyric acid (IBA) and 1-naphthalene acetic acid (NAA) concentrations affected the rooting percentage and seedling rate of D. caryophyllus. Application of NAA at 1000 mg·kg⁻¹ with IBA at 100 mg·kg⁻¹ resulted in the greatest rooting percentage and improved breeding speed. The rooting percentage and seedling rate did not increase with the increase in auxin concentration. Based on these results, we concluded that an appropriate rooting substrate is required to fulfill proper rooting of D. caryohhyllus cuttings, whereas an exogenous application of IBA and NAA at 1000 mg·kg⁻¹ and 100 mg·kg⁻¹ promoted the rooting and a higher auxin concertation inhibited rooting.

The application of diffuse light can potentially improve the homogeneity of light distribution and other microclimatic factors such as temperature inside greenhouses. In this study, diffuse light plastic films with different degrees of light diffuseness (20% and 29%) were used as the south roof cover of Chinese solar greenhouses to investigate the spatial distribution of microclimatic factors and their impacts on the growth and yield of tomato. The horizontal and vertical photosynthetic photon flux density (PPFD) distributions, air temperature distribution, and leaf temperature distribution inside the canopy, tomato leaf net photosynthesis (P_n), and fruit production during the growth period were determined. The results showed that diffuse light plastic film continuously improved the light distribution in the vertical and horizontal spaces of the crop canopy in terms of light interception and uniformity. A more diffuse light fraction also decreased the air and leaf temperatures of the middle canopy and upper canopy during the summer, thereby promoting the photosynthesis of the tomato plants. P_n of the middle and lower canopies with higher haze film were significantly greater than those with lower haze film (19.0% and 27.2%, respectively). The yields of higher stem density and lower stem density planted tomatoes in the 29% haze compartment were increased by 5.5% and 12.9% compared with 20% in the haze group, respectively. Diffuse light plastic films can improve the homogeneity of the canopy light distribution and increase crop production in Chinese solar greenhouses.

Height control is a major consideration during commercial production of chrysanthemum [Dendranthema×grandiflora Kitam. (syn. Chrysanthemum×morifolium Ramat.)]. We have addressed this problem by a biotechnological approach. Plants of `Iridon' chrysanthemum were genetically engineered to ectopically express a tobacco (Nicotiana tabacum L.) phytochrome B1 gene under the control of the CaMV 35S promoter. The transgenic plants were shorter in stature and had larger branch angles than wild type (WT) plants. Reduction in growth caused by the ectopic expression of the tobacco phytochrome B1 gene was similar to that caused using a commercial growth retardant at the recommended rate. Another morphological effect observed in the leaves of the transgenic plants was more intense green color that was related to higher levels of chlorophyll. The transgenic plants appeared very similar to WT plants grown under a filter that selectively attenuated far red wavelengths. Furthermore, when plants were treated either with gibberellin A₃ (which promoted growth) or 2-chlorocholine chloride, an inhibitor of gibberellin biosynthesis (which inhibited growth) the difference in the average internode length between the transgenic plants and WT plants was the same in absolute terms. This suggests that reduction of growth by the expressed PHY-B1 transgene did not directly involve gibberellin biosynthesis. The commercial application of this biotechnology could provide an economic alternative to the use of chemical growth regulators, thereby reducing production costs.

Plant architecture is a major consideration during the commercial production of chrysanthemum (Dendranthema grandiflora Tzvelev). We have addressed this problem through a biotechnological approach: genetic engineering of chrysanthemum cv. Iridon plants that ectopically expressed a tobacco phytochrome B1 gene under the control of the CaMV 35S promoter. The transgenic plants were shorter, greener in leaves, and had larger branch angles than wild-type (WT) plants. Transgenic plants also phenocopied WT plants grown under light condition depleted of far-red wavelengths. Furthermore, the reduction of growth by the expressed PHY-B1 transgene did not directly involve gibberellins. The commercial application of this biotechnology could provide an economic alternative to the use of chemical growth regulators, and thus reduce the production cost.

Aquaporin (AQP) proteins can transport water and other small molecules through cellular membranes and are one of the first targets of stress-induced signaling in plants. A number of AQP genes have been identified from glycophytes, and their functions have been studied. However, the reports on AQPs from halophytes and their precise role in abiotic stress response are still rare. In this study, we have identified a PIP1 subgroup AQP gene, designated SbPIP1, from the euhalophyte Salicornia bigelovii and characterized it by overexpressing in tobacco plants. SbPIP1 transcript was induced by cold, but suppressed by NaCl and polyethylene glycol (PEG). Transient expression of GFP (green fluorescent protein)-SbPIP fusion protein indicated its localization in the plasma membrane. Overexpression of SbPIP1 in tobacco (Nicotiana tabacum) plants increased their drought tolerance. Leaf protoplasts from transgenic tobacco plants absorbed water more quickly than those from wild type (WT) plants when they were put into hypotonic solution. In addition, the transgenic tobacco plants possessed higher relative water content (RWC) and proline content, but lower levels of malondialdehyde (MDA) and less ion leakage (IL) when compared with WT under the treatment of the different concentrations of PEG. Taken together, our results demonstrate that heterologous expression of SbPIP1 in tobacco plants confers them drought stress tolerance by reducing membrane injury and increasing the ability to retain water.

Ginkgo biloba L. (ginkgo) is generally regarded as a tolerant species to environmental stresses. However, its tolerance mechanisms are not well understood, particularly for salt stress. To evaluate the species’ physiological responses to salt stress, 3-year-old ginkgo seedlings were exposed to a range of salinity levels (0% to 1.0% NaCl). A significant reduction in maximum (F _v/F _m) and actual (Φ_PSII) quantum yields of photosystem II (PSII) photochemistry and the nonphotochemical quenching (q_N) coefficient only occurred in late treatment stages at the salinity levels of 0.6% to 1.0%. As salt concentration increased, the response time and chlorophyll (Chl) fluorescence indices decreased. Overall, the activities of superoxide dismutase (SOD) and peroxidase (POD); contents of catalase (CAT), reduced glutathione (GSH), and flavonoids; and scavenging rate of free radicals enhanced under salinity stress. These data indicate that ginkgo seedlings are tolerant to low salt stress, and enzymatic and nonenzymatic antioxidant systems seem to work synergistically to reduce lipid oxidation under NaCl stress because malondialdehyde (MDA) content did not increase. Correlation and principal component analyses determined that water potential, Chl fluorescence parameters, activities of POD and SOD, contents of CAT and flavonoids, and hydroxyl (•OH) and diphenyl picrylhydrazyl (DPPH) free radical scavenging capability were sensitive to salt stress. These parameters can be used for in vitro or rapid and nondestructive monitoring of the responses of ginkgo seedlings to salinity stress. It is of significance to understand the tolerance mechanisms of ginkgo to salt stress, reduce the harm of NaCl and other snow-melting agents to ginkgo as shade trees, and develop new salt-tolerant varieties.

To compare the effects of various zinc (Zn) foliar fertilizers on correcting citrus Zn deficiency and to explore an effective correcting method, three common Zn fertilizers, Zn sulfate heptahydrate (ZnSO₄.7H₂O), Zn chloride (ZnCl₂), and Zn nitrate hexahydrate [Zn(NO₃)₂.6H₂O], were selected to spray the Zn-deficient citrus leaves, tested at different concentrations, with or without organosilicone surfactant. Zn content, chlorophyll levels, and photosynthesis characteristics of leaves were analyzed. Leaf Zn content was significantly increased with increase of the sprayed Zn concentration of the three Zn fertilizers. However, when the sprayed Zn concentration of ZnSO₄.7H₂O exceeded 200 mg·L⁻¹, and Zn concentration of ZnCl₂ or Zn(NO₃)₂.6H₂O exceeded 100 mg·L⁻¹, obvious necrotic spots formed on leaves. This necrosis disappeared when 0.025% organosilicone was added to the three Zn fertilizer solutions, even at a Zn concentration of 250 mg·L⁻¹. Meanwhile, the Zn contents of leaves increased one to four times for these treatments. Furthermore, foliar application of the three Zn fertilizers significantly improved chlorophyll levels and photosynthetic capacity of Zn-deficient leaves. The data of chlorophyll and photosynthesis characteristics indicate that the correcting effect of ZnCl₂ and Zn(NO₃)₂.6H₂O is better than that of ZnSO₄.7H₂O, and could be further improved via supplement of organosilicone. In conclusion, ZnCl₂ or Zn(NO₃)₂.6H₂O containing 250 mg·L⁻¹ of Zn and supplemented with 0.025% organosilicone is a safe and effective formulation of Zn foliar fertilizer for correcting citrus Zn deficiency.

The aim of the present study was to evaluate the effects of alternating red (660 nm) and blue (460 nm) light on the growth and nutritional quality of two-leaf-color pak choi (Brassica campestris L. ssp. chinensis var. communis). Four light treatments (supplemental alternating red and blue light with intervals of 0, 1, 2, and 4 hours, with a monochromatic light intensity of 100 μmol·m⁻²·s⁻¹ and a cumulative lighting time of 16 hours per day) were conducted in a greenhouse under identical ambient light conditions (90 to 120 μmol·m⁻²·s⁻¹ at 12:00 am) for 10 days before green- and red-leaf pak choi were harvested. The results showed that the two-leaf-color pak choi receiving alternating red and blue light exhibited more compact canopies and wider leaves than those under the control treatment, which was attributed to the shade avoidance syndrome of plants. The present study indicated that the biomass of green-leaf pak choi was much higher than that of red-leaf pak choi, but the nutritional quality of green-leaf pak choi was lower than that of red-leaf pak choi, and seemingly indicating that the regulation of metabolism for pak choi was species specific under light exposure. The trends of both biomass and the soluble sugar content were highest under the 1-hour treatment. The contents of chlorophyll a and total chlorophyll in both cultivars (green- and red-leaf pak choi) were significantly increased compared with control, without significant differences among the 1-, 2-, and 4-hour treatments, whereas chlorophyll b exhibited no significant difference in any treatment. Alternating red- and blue-light treatment significantly affected the carotenoid content, but different trends in green- and red-leaf pak choi were observed, with the highest contents being detected under the 1-hour and 4-hour treatments, respectively. With increasing time intervals, the highest soluble protein contents in two-leaf-color pak choi were observed in the 4-hour treatment, whereas nitrate contents were significantly decreased in the 4-hour treatment. Compared with 0 hours, the contents of vitamin C, phenolic compounds, flavonoids, and anthocyanins in two-leaf-color pak choi were significantly increased, but no significant differences were observed in vitamin C, phenolic compounds, and flavonoids among the 1-, 2-, and 4-hour treatments, similar to what was found for the anthocyanin content of green-leaf pak choi. However, the content of anthocyanins in red-leaf pak choi gradually increased with increasing time intervals, with the highest content being found in the 4-hour treatment. Supplemental alternating red and blue light slightly increased the antioxidant capacity [1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate and antioxidant power], but no significant differences were observed after 1, 2, and 4 hours of treatment. Taken together, treatment with an interval of 1 hour was the most effective for increasing the biomass of pak choi in this study, but treatment with a 4-hour interval should be considered to enhance the accumulation of health-promoting compounds.

Petal anthocyanins were systematically identified and characterized by high-performance liquid chromatography (HPLC)–electrospray ionization–mass spectrometry (MS) coupled with diode array detection among nine wild herbaceous peony (Paeonia L.) species (15 accessions). Individual anthocyanins were identified according to the HPLC retention time, elution order, MS fragmentation patterns, and by comparison with authentic standards and published data. Six main anthocyanins, including peonidin-3,5-di-O-glucoside, peonidin-3-O-glucoside-5-O-arabinoside (Pn3G5Ara), peonidin-3-O-glucoside, pelargonidin-3,5-di-O-glucoside, cyanidin-3,5-di-O-glucoside, and cyanidin-3-O-glucoside (Cy3G), were detected. In addition to the well-known major anthocyanins, some minor anthocyanins were identified in herbaceous peony species for the first time. Detection of the unique anthocyanins cyanidin-3-O-glucoside-5-O-galactoside and pelargonidin-3-O-glucoside-5-O-galactoside in both Paeonia anomala L. and P. anomala ssp. veitchii (Lynch) D.Y. Hong & K.Y. Pan indicated these two species should belong to the same taxon. Pn3G5Ara was found only in European wild species and subspecies suggesting different metabolic pathways between European and Chinese accessions. Anthocyanins conjugated with galactose and arabinose were observed in the genus Paeonia for the first time. The North American species, Paeonia tenuifolia L., had high Cy3G content in flower petals. This anthocyanin composition is distinct from the anthocyanin composition in Asian and European species and possibly is responsible for the vivid red coloration in flowers.