Artificial Light for Improving Tomato Recovery Following Grafting: Transcriptome and Physiological Analyses.

Grafting is widely used to enhance the phenotypic traits of tomatoes, alleviate biotic and abiotic stresses, and control soil-borne diseases of the scion in greenhouse production. There are many factors that affect the healing and acclimatization stages of seedlings after grafting. However, the role of light has rarely been studied. In this study, we compared the effects of artificial light and traditional shading (under shaded plastic-covered tunnels) on the recovery of grafted tomato seedlings. The results show that the grafted tomato seedlings recovered using artificial light had a higher healthy index, leaf chlorophyll content, shoot dry weight, and net photosynthetic rate (Pn) and water use efficiency (WUE) compared with grafted seedling recovered using the traditional shading method. Transcriptome analysis showed that the differentially expressed genes (DEGs) of grafted seedlings restored using artificial light were mainly enriched in the pathways corresponding to plant hormone signal transduction. In addition, we measured the endogenous hormone content of grafted tomato seedlings. The results show that the contents of salicylic acid (SA) and kinetin (Kin) were significantly increased, and the contents of indoleacetic acid (IAA) and jasmonic acid (JA) were decreased in artificial-light-restored grafted tomato seedlings compared with those under shading treatments. Therefore, we suggest that artificial light affects the morphogenesis and photosynthetic efficiency of grafted tomato seedlings, and it can improve the performance of tomato seedlings during grafting recovery by regulating endogenous hormone levels.

Effects of different light intensity on the growth of tomato seedlings in a plant factory.

Light-emitting diodes (LEDs) were the best artificial light source for plant factories. Red light-emitting diodes (LEDs, R) and blue light-emitting diodes (LEDs, B) were used to obtain different light intensities of uniform spectra, and the greenhouse environment was considered as a comparison. The results showed that root dry weight, shoot dry weight and stem diameter were superior in plant growth under 240 µmolm-2s-1, additionally, the Dixon Quality Index (DQI) was also best. Under 240 µmolm-2s-1, the net photosynthesis rate (Pn) was consistent with the greenhouse's treatment, superior to other experimental groups. The results implied that the PPFD was more suitable for the cultivation of tomato seedlings under the condition of 240 µmolm-2s-1, and can replace the greenhouse conditions so as to save energy and reduce emissions.

Comparison of rockwool and coir for greenhouse cucumber production: chemical element, plant growth, and fruit quality.

Replacing rockwool with more sustainable materials, such as coir, is an effective measure to improve the sustainability of soilless cultivation in the greenhouse. To comprehensively assess the feasibility of coir before using it widely, coir was compared to rockwool as a cucumber cultivation substrate to evaluate its performance on mineral elements in the substrates, drainage, and in the plants. Plant growth, amino acids, and flavor substances of cucumber fruits were also compared between the two substrates. Compared to rockwool, coir significantly increased the LAI and yield of cucumber crops as well as contents of Ca, Mg, S, Cl and Zn in leaves and fruits. Contents of P, K, Ca, Mg, Cl, Zn, and B in the substrate were higher for coir while those of Fe, Cu, and Mn in the drainage lower. Moreover, coir also significantly increased contents of amino acids (His, Leu, Ile, Phe, Lys, Asp, Glu and Pro) and flavor substance (TC, PS, TP, CLL, CuB, and LA) in cucumber fruits. Our results demonstrated the potential of coir as a replacement of rockwool to improve sustainability of soilless cultivation in the greenhouse.

Zero Discharge of Nutrient Solution to the Environment in a Soilless Greenhouse Cucumber Production System.

With the development of the economy and society, more attention is being paid to energy costs and the potential environmental pollution caused by vegetable cultivation. The aim of this study was to investigate the impacts of zero discharge of nutrient solutions on cucumber growth, leaf photosynthesis, and the yield and quality of cucumber under greenhouse conditions. The results show that zero discharge treatment did not change plant height, stem diameter, internode length, leaf area, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), and leaf relative chlorophyll content on the most measurement days. Only Pn and relative chlorophyll content were significantly reduced after 16 days of treatment but soon recovered over time. Cucumber plants can adapt to treatment circumstances over the course of days. Leaf mineral element contents showed significant differences on some treatment days compared to the control, and trace elements of Fe, Mn, Cu, and Mo can be appropriately supplied during the treatment days. The cucumber yield and fruit quality in the zero discharge treatment did not change during the whole experimental period. This study confirmed that the irrigation method of a nutrient solution with zero discharge can be applied in cucumber cultivation practices. The strict management of irrigation strategy, plant growth, and greenhouse climate are very important for zero discharge cultivation. The cultivation method with zero discharge of nutrient solution can reduce the energy costs of disinfection, save water and fertilizers, and reduce the environmental pollution in cucumber cultivation.