Effect of exogenous calcium on physiological characteristics of salt tolerance in Tartary buckwheat

Calcium signal regulated carbohydrate metabolism in wheat seedlings under salinity stress

This study aimed to explore the mechanism by which calcium (Ca) signal regulated carbohydrate metabolism and exogenous Ca alleviated salinity toxicity. Wheat seedlings were treated with sodium chloride (NaCl, 150 mM) alone or combined with 500 μM calcium chloride (CaCl2), lanthanum chloride (LaCl3) and/or ethylene glycol tetraacetic acid (EGTA) to primarily analyse carbohydrate starch and sucrose metabolism, as well as Ca signaling components. Treatment with NaCl, EGTA, or LaCl3 alone retarded wheat-seedling growth and decreased starch content accompanied by weakened ribulose-1,5-bisphosphate carboxylation/oxygenase (Rubisco) and Rubisco activase activities, as well as enhanced glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, alpha-amylase, and beta-amylase activities. However, it increased the sucrose level, up-regulated the sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) activities and TaSPS and TaSuSy expression together, but down-regulated the acid invertase (SA-Inv) and alkaline/neutral invertase (A/N-Inv) activities and TaSA-Inv and TaA/N-Inv expression. Except for unchanged A/N-Inv activities and TaA/N-Inv expression, adding CaCl2 effectively blocked the sodium salt-induced changes of these parameters, which was partially eliminated by EGTA or LaCl3 presence. Furthermore, NaCl treatment also significantly inhibited Ca-dependent protein kinases and Ca2+-ATPase activities and their gene expression in wheat leaves, which was effectively relieved by adding CaCl2. Taken together, CaCl2 application effectively alleviated the sodium salt-induced retardation of wheat-seedling growth by enhancing starch anabolism and sucrose catabolism, and intracellular Ca signal regulated the enzyme activities and gene expression of starch and sucrose metabolism in the leaves of sodium salt-stressed wheat seedlings.

Heat Stress Alleviation by Exogenous Calcium in the Orchid Dendrobium nobile Lindl: A Biochemical and Transcriptomic Analysis

The growth of Dendrobium nobile is sensitive to heat stress. To find an effective method for enhancing heat tolerance, this study investigated the relieving effect of exogenous calcium at different concentrations (0 mmol/L, 5 mmol/L, 10 mmol/L, 15 mmol/L, 20 mmol/L CaCl2) on heat stress in D. nobile. Principal component analysis was used to screen the optimal exogenous calcium concentration, and transcriptome analysis was used to reveal its possible heat tolerance mechanism. The results showed that compared with the T0, a 10 mmol/L calcium treatment: increased the average leaf length, leaf width, plant height, and fresh matter accumulation of D. nobile by 76%, 103.39%, 12.97%, and 12.24%, respectively (p < 0.05); significantly increased chlorophyll a (Chla), chlorophyll b (Chlb), carotenoids(Car), ascorbic acid (ASA), glutathione (GSH), and flavonoids by 15.72%, 8.54%, 11.88%, 52.17%, 31.54%, and 36.12%, respectively; and effectively enhanced the enzyme activity of the antioxidant system, increasing superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) by 1.38, 1.61, and 2.16 times, respectively (p < 0.05); At the same time, the treatment can effectively reduce the yellow leaf rate and defoliation rate of D. nobile under heat stress. The principal component analysis method and membership function were used to calculate the D value to rank the relief effects of each calcium treatment group, and the results also showed that 10 mmol/L CaCl2 had the best relief effect. Transcriptomics testing identified 7013 differentially expressed genes, of which 2719 were upregulated, and 294 were downregulated. Among them, genes such as HSPA1s, HSP90A, HSPBP1, ATG8, COMT, REF1, E1.11.1.7, along with transcription factors such as MYB, bHLH, WRKY, and NAC, formed the network of tolerance to heat stress in D. nobile. This study provides new insights for improving the cultivation techniques of D. nobile.

Multi-Omics Revealed Peanut Root Metabolism Regulated by Exogenous Calcium under Salt Stress

High salinity severely inhibits plant seedling root development and metabolism. Although plant salt tolerance can be improved by exogenous calcium supplementation, the metabolism molecular mechanisms involved remain unclear. In this study, we integrated three types of omics data (transcriptome, metabolome, and phytohormone absolute quantification) to analyze the metabolic profiles of peanut seedling roots as regulated by exogenous calcium under salt stress. (1) exogenous calcium supplementation enhanced the allocation of carbohydrates to the TCA cycle and plant cell wall biosynthesis rather than the shikimate pathway influenced by up-regulating the gene expression of antioxidant enzymes under salt stress; (2) exogenous calcium induced further ABA accumulation under salt stress by up-regulating the gene expression of ABA biosynthesis key enzymes AAO2 and AAO3 while down-regulating ABA glycosylation enzyme UGT71C5 expression; (3) exogenous calcium supplementation under salt stress restored the trans-zeatin absolute content to unstressed levels while inhibiting the root cis-zeatin biosynthesis.

Optimal exogenous calcium alleviates the damage of Snow-melting agent to Salix matsudana seedlings

As the main component of snowmelt agents, NaCl is widely used in northern winters and significantly impacts the expected growth of garden plants in north China. Salix matsudana is also faced with salt stress caused by snowmelt, which seriously affects its development as the main tree species in the northern landscape. However, how exogenous calcium alleviates salt stress in Salix matsudana is not yet clear. In this study, the indicators of growth indices, photosynthetic characteristics and stress resistance were measured by hydroponic assays in combination with three NaCl conditions (0, 50 and 200 mmol·L^-1) and five calcium concentrations (0, 2.5, 5, 10 and 20 mmol·L^-1). The study's results indicated that the application of exogenous calcium remarkably promoted the growth of Salix matsudana seedlings under NaCl stress. When the exogenous calcium concentration was 10 mmol·L^-1, the plant height and basal diameter of Salix matsudana seedlings increased significantly, and the biomass of all parts reached the maximum (P< 0.05). Exogenous calcium can substantially improve the photosynthesis of Salix matsudana seedlings under salt stress. The photosynthetic parameters, photosynthetic pigment content and photosynthetic product synthesis of Salix matsudana seedlings were significantly increased at an exogenous calcium concentration of 10 mmol·L^-1, and the photosynthetic level of Salix matsudana seedlings reached the highest value. The chlorophyll fluorescence parameters (F _v /F _m, F _v /F ₀) of Salix matsudana seedlings were significantly decreased under different concentrations of NaCl stress. The maximum photochemical efficiency (F _v /F _m) and potential photochemical efficiency (F _v /F ₀) of Salix matsudana seedlings peaked when the exogenous calcium concentration was 10 mmol·L^-1, which was significantly higher than that of the other treatments (P< 0.05). The water use efficiency of Salix matsudana was affected considerably by NaCl stress. The WUE and iWUE peak values of Salix matsudana were significantly higher than those of other calcium concentrations at 10 mmol·L^-1 (P< 0.05). Exogenous calcium can increase the activities of CAT, SOD and POD enzymes in Salix matsudana seedlings under different NaCl concentrations. Under NaCl stress, adding exogenous calcium promoted the survival rate and growth of Salix matsudana seedlings. In conclusion, the optimum exogenous calcium concentration for Salix matsudana seedlings was 10 mmol·L^-1. High or low concentrations of exogenous calcium did not achieve the best results in alleviating salt stress in Salix matsudana.

Identification of Tartary Buckwheat Varieties Suitable for Forage via Nutrient Value Analysis at Different Growth Stages

It is important to select buckwheat varieties suitable for foraging and determining their best harvest time as increasing attention was paid to the forage value of buckwheat. Here, eight tartary buckwheat varieties were identified as suitable for forage based on their potential forage value through assaying the contents of ash, crude protein, crude fiber, crude fat, acid detergent fiber, neutral detergent fiber, nitrogen free extract, calcium, phosphorus, total flavonoids, and rutin in these tartary buckwheat varieties at flowering, pustulation, and mature stages, respectively. In addition, analysis of relative feed value (RFV), relative forage quality (RFQ), and principal component analysis (PCA) based on the assayed contents was applied for comprehensive evaluation of these tartary buckwheat varieties. Results showed that all the eight tartary buckwheat varieties possessed potential high forage value as their RFV is from 121.31% to 217.39% and RFQ from 117.26% to 224.54% at all three stages. In particular, both RFV and RFQ values of PS-07 reached the highest at the flowering stage among the eight tartary buckwheat varieties, followed by CQ-3 and EWPS. Accordingly, the comprehensive scoring of principal component values of PS-07 and CQ-3 are relatively higher at the flowering stage. Our research thus revealed that the eight tartary buckwheat varieties are all suitable for forage, and also provided an experimental basis for selecting the eight tartary buckwheat varieties harvested at different growth stages for livestock forage.