Green Light Partial Replacement of Red and Blue Light Improved Drought Tolerance by Regulating Water Use Efficiency in Cucumber Seedlings

Abstract

Light is one of the most important environmental signals in plant growth, development, and stress response. Green light has been proved to enhance plant defense against biotic and/or abiotic stress. To illustrate the effects of green light partially replaced red light and blue light on the plant under drought condition, cucumber (Cucumis sativus L. cv. Xinchun No. 4) seedlings were treated with short-term drought stress and were concomitantly exposed to four treatments, which were set up by adjusting the relative amount of green light as 0 (RB), 25 (RBG25), 50 (RBG50), and 75 (RBG75) μmol m−2 s−1, respectively, with a total photosynthetic photon flux density of 250 μmol m−2 s−1 and a fixed red-to-blue ratio of 4:1. The results showed that compared with RB, RBG50 significantly increased shoot fresh weight (FW) and dry weight (DW), root DW, plant height, stem diameter, leaf area, and leaf dry mass per unit area (LMA) by 10.61, 7.69, 66.13, 6.22, 10.02, 4.10, and 12.41%, respectively. Also, the addition of green light significantly increased the root volume and root tip number. Moreover, green light partial replacement of red light and blue light increased total water content, especially free water content, improved leaf water status, and alleviated water loss in plants caused by drought stress. Also, the addition of green light increased net photosynthetic rate (Pn), reduced both stomata conductance (gs) and transpiration rate (E), enhanced the intrinsic water-use efficiency (WUE) and instantaneous water-use efficiency (iWUE) of leaves, and increased the content of chlorophylls a and b. Green light substituting a proportion of blue and red light regulated stomatal aperture by significantly increasing abscisic acid (ABA) and γ-aminobutyric acid (GABA) content. In addition, the increase of GABA was resulted from the upregulation of Glutamate Decarboxylase 2 (CsGAD2). However, the relative electrolytic leakage and contents of malondialdehyde (MDA), superoxide anion (O2−), and hydrogen peroxide (H2O2) vigorously decreased as the intensity of green light was added to the spectrum under drought. Conclusively, green light partially replaced red light and blue light and improved drought tolerance of cucumber seedlings by upregulating the expression of CsGAD2 gene and promoting the synthesis of GABA. The increase in GABA content further downregulated the expression of aluminum-activated malate transporter 9 (CsALMT9) gene, induced stomata to close, improved water utilization, and alleviated damage caused by drought. This study highlights a role of green light in plant physiological processes. Moreover, analyzing the function of green light on improving drought tolerance of plants could open alternative avenues for improving plant stress resilience.

Response of Strawberry to the Substitution of Blue Light by Green Light in an Indoor Vertical Farming System

“…However, in our study, leaf and fruit Ca were highest in plants grown under high GL proportion (27%) despite its low transpiration rate. This result may be due to the high root biomass compared to plants with 6% of GL (52% and 61% in dry biomass increase in plants with 27% and 20% GL), thus, the promotion of root growth may have resulted in higher root branching and formation of root apices, as reported by Ma et al [36] in cucumber plants under increased GL proportion. As Ca is preferably acquired in the root's tip where the Casparian strip is not formed [37], the promoted root growth observed in plants illuminated with GL may have resulted in increased Ca uptake.…”

E3 ubiquitin ligase OsPIE3 destabilises the B‐lectin receptor‐like kinase PID2 to control blast disease resistance in rice

“…The cleared samples were mounted in 50% glycerol for imaging. The presence of brown regions/spots on leaves indicates the presence of H 2 O 2 (Wang et al ., 2021; Ma et al ., 2022), the content of which was determined using an H 2 O 2 reagent test kit (BC3590; Solarbio, Beijing, China), according to the manufacturer's protocol.…”