Effects of Potassium-Containing Fertilizers on Sugar and Organic Acid Metabolism in Grape Fruits.

To identify suitable potassium fertilizers for grape (Vitis vinifera L.) production and study their mechanism of action, the effects of four potassium-containing fertilizers (complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate) on sugar and organic acid metabolism in grape fruits were investigated. Potassium-containing fertilizers increased the activity of sugar and organic acid metabolism-related enzymes at all stages of grape fruit development. During the later stages of fruit development, potassium-containing fertilizers increased the total soluble solid content and the sugar content of the different sugar fractions and decreased the titratable acid content and organic acid content of the different organic acid fractions. At the ripening stage of grape fruit, compared with the control, complex fertilizer, potassium nitrate, potassium sulfate, and potassium dihydrogen phosphate increased the total soluble solid content by 1.5, 1.2, 3.5, and 3.4 percentage points, decreased the titratable acid content by 0.09, 0.06, 0.18, and 0.17 percentage points, respectively, and also increased the total potassium content in grape fruits to a certain degree. Transcriptome analysis of the differentially expressed genes (DEGs) in the berries showed that applying potassium-containing fertilizers enriched the genes in pathways involved in fruit quality, namely, carbon metabolism, carbon fixation in photosynthetic organisms, glycolysis and gluconeogenesis, and fructose and mannose metabolism. Potassium-containing fertilizers affected the expression levels of genes regulating sugar metabolism and potassium ion uptake and transport. Overall, potassium-containing fertilizers can promote sugar accumulation and reduce acid accumulation in grape fruits, and potassium sulfate and potassium dihydrogen phosphate had the best effects among the fertilizers tested.

Transcriptome and biochemical analyses reveal phenolic compounds-mediated flavor differences in loquat (Eriobotrya japonica Lindl.) cultivars Chunhua No.1 and Dawuxing.

The novel loquat cultivar 'Chunhua No.1' (CH1) is a promising commercial cultivar. However, CH1 has texture characteristics different from those of common loquat, and its formation mechanism remains unclear. Here, we first identified the phenolic compounds of CH1 and its parent ('Dawuxing', DWX) and the effect on texture formation. The special presence of stone cells explained the flavor differences in CH1. Chlorogenic acid, neochlorogenic acid, and coniferyl alcohol were the main phenolic compounds in loquat, and the high content of coniferyl alcohol was a potential factor for the rough texture of CH1. Transcriptome reveals that phenylpropanoid metabolism was activated during CH1 fruit texture formation. Kyoto Encyclopedia of Genes and Genomes (KEGG) identified 51 structural genes involved in phenylpropanoid biosynthesis, and Weighted Gene Co-expression Network Analysis (WGCNA) identified four structural genes and 88 transcription factors. These findings provide new insights into the phenolic metabolism and flavor formation of loquat fruit.

Melatonin and 14-hydroxyed brassinosteroid combined promote kiwifruit seedling growth by improving soil microbial distribution, enzyme activity and nutrients uptake.

Kiwifruit, a nutrient-dense fruit, has become increasingly popular with consumers in recent decades. However, kiwifruit trees are prone to stunted growth after a few years of planting, called early tree decline. In this study, melatonin (MT), pollen polysaccharide (SF), 14-hydroxyed brassinosteroid (14-HBR) were applied alone or in combination to investigate their influence on plant growth, nutrition absorption and rhizosphere bacterial abundance in kiwifruit seedlings. The results revealed that MT, SF and 14-HBR alone treatments significantly increased leaf chlorophyll content, photosynthetic capacity and activities of dismutase and catalase compared with the control. Among them, MT treatment significantly increased the dry root biomass by 35.7%, while MT+14-HBR treatment significant enhanced the dry shoot biomass by 36.9%. Furthermore, both MT and MT+14-HBR treatments markedly improved the activities of invertase, urease, protease and phosphatase in soil, as well as the abundance of Proteobacteria and Acidobacteria in rhizosphere microorganisms based on 16S rDNA sequencing. In addition, MT treatment improved the content of available K and organic matter in soil, and increased the uptake of P, K and Fe by seedlings. In summary, 14-HBR and MT combined had the best effect on promoting rhizosphere bacterial distribution, nutrient absorption and plant growth. These findings may provide valuable guidance for solving growth weakness problem in kiwifruit cultivation.

Methylation of AcGST1 Is Associated with Anthocyanin Accumulation in the Kiwifruit Outer Pericarp.

Most red-fleshed kiwifruit cultivars, such as Hongyang, only accumulate anthocyanins in the inner pericarp; the trait of full red flesh becomes the goal pursued by breeders. In this study, we identified a mutant "H-16" showing a red color in both the inner and outer pericarps, and the underlying mechanism was explored. Through transcriptome analysis, a key differentially expressed gene AcGST1 was screened out, which was positively correlated with anthocyanin accumulation in the outer pericarp. The result of McrBC-PCR and bisulfite sequencing revealed that the SG3 region (-292 to -597 bp) of AcGST1 promoter in "H-16" had a significantly lower CHH cytosine methylation level than that in Hongyang, accompanied by low expression of methyltransferase genes (MET1 and CMT2) and high expression of demethylase genes (ROS1 and DML1). Transient calli transformation confirmed that demethylase gene DML1 can activate transcription of AcGST1 to enhance its expression. Overexpression of AcGST1 enhanced the anthocyanin accumulation in the fruit flesh and leaves of the transgenic lines. These results suggested that a decrease in the methylation level of the AcGST1 promoter may contribute to accumulation of anthocyanin in the outer pericarp of "H-16".

Anti-Oomycete Effect and Mechanism of Salicylic Acid on Phytophthora infestans.

Pathogenic oomycetes infect a wide variety of organisms, including plants, animals, and humans, and cause massive economic losses in global agriculture, aquaculture, and human health. Salicylic acid (SA), an endogenous phytohormone, is regarded as an inducer of plant immunity. Here, the potato late blight pathogen Phytophthora infestans was used as a model system to uncover the inhibitory mechanisms of SA on pathogenic oomycetes. In this research, SA significantly inhibited the mycelial growth, sporulation, sporangium germination, and virulence of P. infestans. Inhibition was closely related to enhanced autophagy, suppression of translation initiation, and ribosomal biogenesis in P. infestans, as shown by multiomics analysis (transcriptomics, proteomics, and phosphorylated proteomics). Monodansylcadaverine (MDC) staining and Western blotting analysis showed that SA promoted autophagy in P. infestans by probably targeting the TOR signaling pathway. These observations suggest that SA has the potential to control late blight caused by P. infestans.

Melatonin Promotes Iron Reactivation and Reutilization in Peach Plants under Iron Deficiency.

The yellowing of leaves due to iron deficiency is a prevalent issue in peach production. Although the capacity of exogenous melatonin (MT) to promote iron uptake in peach plants has been demonstrated, its underlying mechanism remains ambiguous. This investigation was carried out to further study the effects of exogenous MT on the iron absorption and transport mechanisms of peach (Prunus persica) plants under iron-deficient conditions through transcriptome sequencing. Under both iron-deficient and iron-supplied conditions, MT increased the content of photosynthetic pigments in peach leaves and decreased the concentrations of pectin, hemicellulose, cell wall iron, pectin iron, and hemicellulose iron in peach plants to a certain extent. These effects stemmed from the inhibitory effect of MT on the polygalacturonase (PG), cellulase (Cx), phenylalanine ammonia-lyase (PAL), and cinnamoyl-coenzyme A reductase (CCR) activities, as well as the promotional effect of MT on the cinnamic acid-4-hydroxylase (C4H) activity, facilitating the reactivation of cell wall component iron. Additionally, MT increased the ferric-chelate reductase (FCR) activity and the contents of total and active iron in various organs of peach plants under iron-deficient and iron-supplied conditions. Transcriptome analysis revealed that the differentially expressed genes (DEGs) linked to iron metabolism in MT-treated peach plants were primarily enriched in the aminoacyl-tRNA biosynthesis pathway under iron-deficient conditions. Furthermore, MT influenced the expression levels of these DEGs, regulating cell wall metabolism, lignin metabolism, and iron translocation within peach plants. Overall, the application of exogenous MT promotes the reactivation and reutilization of iron in peach plants.

Transcriptome Profiles Reveal the Promoting Effects of Exogenous Melatonin on Fruit Softening of Chinese Plum.

In this study, we investigated the effect of exogenous melatonin (MT) on cell wall metabolism leading to Chinese plum (Prunus salicina Lindl.) fruit softening. Exogenous MT treatment increased the endogenous MT content in plum fruits before fruit ripening. However, in mature plum fruits, exogenous MT treatment decreased the fruit hardness, pulp hardness, fruit elasticity, contents of ion-bound pectin, covalently-bound pectin, hemicellulose, and cellulose, and activities of xyloglucan endotransglycosylase/hydrolase and endo-ß-1,4-glucanase, and increased the water-soluble pectin content, and activities of pectin methyl esterase, pectin lyase, polygalacturonase, ß-galactopyranosidase, and α-L-arabinofuranosidase. Transcriptome analysis revealed that the differentially expressed genes (DEGs) associated with cell wall metabolism in the exogenous MT-treated plum fruits were mainly enriched in the pentose and glucuronate interconversions, phenylpropanoid biosynthesis, cyanoamino acid metabolism, and galactose metabolism pathways. Analysis of these DEGs revealed that exogenous MT treatment affected the expression of genes regulating the cell wall metabolism. Overall, exogenous MT treatment promotes the fruit softening of Chinese plum.

Comparative Analysis of Carotenoid Profiles and Biosynthetic Gene Expressions among Ten Plum Cultivars.

Plums are good sources of various bioactive phytochemical compounds such as vitamins, anthocyanins, and carotenoids, whereby all of which are noted for multiple potential health benefits. However, knowledge regarding plum carotenoid profiles remains limited. Hence, the total and individual carotenoids in the edible parts (skin and flesh) of ten plum cultivars were determined using a spectrophotometer and high-performance liquid chromatography-diode array detection, respectively. Total and individual carotenoid contents in skin were significantly higher (p < 0.05) than those in flesh among all plum cultivars tested. The cultivars with the highest content of total carotenoids in skin were Naili (36.73 µg/g FW), followed by Yinhongli (21.81 µg/g FW) and Yuhuangli (19.70 µg/g FW), with the lowest in Angeleno (8.97 µg/g FW). Lutein, zeaxanthine, ß-cryptoxanthin, α-carotene, and ß-carotene were the major types of carotenoids detected, with lutein and ß-carotene being the predominant constituents of the skin and flesh tissues, respectively. Lutein, zeaxanthine, and total carotenoid contents were positively correlated with the expressions of PSY, LCYB, and LCYE, and negatively correlated with the expressions of PDS and CRTISO. Characterizing the carotenoid profiles and investigating variations in carotenoid biosynthetic gene expressions among plum cultivars are crucial for advancing genetic improvements in plums.

Genome-wide identification of the AcMADS-box family and functional validation of AcMADS32 involved in carotenoid biosynthesis in Actinidia.

MADS-box is a large transcription factor family in plants and plays a crucial role in various plant developmental processes; however, it has not been systematically analyzed in kiwifruit. In the present study, 74 AcMADS genes were identified in the Red5 kiwifruit genome, including 17 type-I and 57 type-II members according to the conserved domains. The AcMADS genes were randomly distributed across 25 chromosomes and were predicted to be mostly located in the nucleus. A total of 33 fragmental duplications were detected in the AcMADS genes, which might be the main force driving the family expansion. Many hormone-associated cis-acting elements were detected in the promoter region. Expression profile analysis showed that AcMADS members had tissue specificity and different responses to dark, low temperature, drought, and salt stress. Two genes in the AG group, AcMADS32 and AcMADS48, had high expression levels during fruit development, and the role of AcMADS32 was further verified by stable overexpression in kiwifruit seedlings. The content of α-carotene and the ratio of zeaxanthin/ß-carotene was increased in transgenic kiwifruit seedlings, and the expression level of AcBCH1/2 was significantly increased, suggesting that AcMADS32 plays an important role in regulating carotenoid accumulation. These results have enriched our understanding of the MADS-box gene family and laid a foundation for further research of the functions of its members during kiwifruit development.

AcMADS32 positively regulates carotenoid biosynthesis in kiwifruit by activating AcBCH1/2 expression.

Fruits provide abundant carotenoid nutrients for humans, whereas the understanding of the transcriptional regulatory mechanisms of carotenoids in fruits is still limited. Here, we identified a transcription factor AcMADS32 in kiwifruit, which was highly expressed in the fruit, correlated with carotenoid content and localized in the nucleus. The silencing expression of AcMADS32 significantly reduced the content of ß-carotene and zeaxanthin and expression of ß-carotene hydroxylase gene AcBCH1/2 in kiwifruit, while transient overexpression increased the accumulation of zeaxanthin, suggesting that AcMADS32 was an activator involved in the transcriptional regulation of carotenoid in fruit. When AcMADS32 was further stably transformed into kiwifruit, the content of total carotenoid and components in the leaves of transgenic lines significantly increased, and the expression level of carotenogenic genes was up-regulated. Moreover, Y1H and dual luciferase reporter experiments confirmed that AcMADS32 directly bound the AcBCH1/2 promoter and activated its expression. Through Y2H assays, AcMADS32 can interact with other MADS transcription factor AcMADS30, AcMADS64 and AcMADS70. These findings will contribute to our understanding of the transcriptional regulation mechanisms underlying carotenoid biosynthesis in plants.

Organic Acid Accumulation and Associated Dynamic Changes in Enzyme Activity and Gene Expression during Fruit Development and Ripening of Common Loquat and Its Interspecific Hybrid.

Loquats have gained increasing attention from consumers and growers for their essential nutrients and unusual phenology, which could help plug a gap period at market in early spring. Fruit acid is a critical contributor to fruit quality. The dynamic changes in organic acid (OA) during fruit development and ripening of common loquat (Dawuxing, DWX) and its interspecific hybrid (Chunhua, CH) were compared, as well as the corresponding enzyme activity and gene expression. At harvest, titratable acid was significantly lower (p ≤ 0.01) in CH (0.11%) than in DWX loquats (0.35%). As the predominant OA compound, malic acid accounted for 77.55% and 48.59% of the total acid of DWX and CH loquats at harvest, followed by succinic acid and tartaric acid, respectively. PEPC and NAD-MDH are key enzymes that participate in malic acid metabolism in loquat. The OA differences in DWX loquat and its interspecific hybrid could be attributed to the coordinated regulation of multiple genes and enzymes associated with OA biosynthesis, degradation, and transport. The data obtained in this work will serve as a fundamental and important basis for future loquat breeding programs and even for improvements in loquat cultural practices.

Significant increases in Donghong kiwifruit yield by a novel umbrella-shaped trellis system and identification of associated molecular mechanisms.

China is the largest kiwifruit producer in the world, accounting for more than half of the total. However, in terms of yield per unit area, China is much lower than the global average and lags behind that of other countries. Yield improvement is of critical importance for the current kiwifruit industry in China. In this study, an improved overhead pergolas trellis (OPT) system, namely, the umbrella-shaped trellis (UST) system, was developed for Donghong kiwifruit, which is now the second most popular and widely cultivated red-fleshed kiwifruit in China. Surprisingly, the estimated yield on the UST system was more than two times higher than that with a traditional OPT, while the external fruit quality was maintained and the internal fruit quality was improved. One of the mechanisms contributing to the yield improvement was the significant promotion of the vegetative growth of canes at 6 ~ 10 mm in diameter by the UST system. The upper canopy of the UST treatment served as a natural shading condition for the lower fruiting canopy and thus had positive effects on the accumulation of chlorophylls and total carotenoids in the fruiting canopy. The most productive zones on the fruiting canes (6 ~ 10 mm in diameter) contained significantly higher (P < 0.05) levels of zeatin riboside (ZR) and auxin (IAA) and ratios of ZR/gibberellin (GA), ZR/abscisic acid (ABA), and ABA/GA. A relatively high carbon/nitrogen ratio may promote the flower bud differentiation process of Donghong kiwifruit. The outcomes of this study provide a scientific basis for manifold increase in production of kiwifruit and contribute to the sustainability of the kiwifruit industry.

Chromosome-scale genome assembly of a natural diploid kiwifruit (Actinidia chinensis var. deliciosa).

The most commercialized kiwifruit, Actinidia chinensis var. deliciosa (Acd), is an allohexaploid (2n = 6x = 174), making high-quality assemblage genome challenging. We previously discovered a rare naturally occurring diploid Acd plant. Here, chromosome-level de novo genome assembly for this diploid Acd was reported, reaching approximately 621.98 Mb in length with contig and scaffold N50 values of 10.08 and 21.09 Mb, respectively, 99.66% of the bases anchored to 29 pseudochromosomes, and 38,990 protein-coding genes and 42.29% repetitive elements annotated. The divergence time of A. chinensis cv. 'Red5' and 'Hongyang' (11.1-27.7 mya) was more recent compared with the divergence time of them and Acd (19.9-41.2 mya), with the divergence time of A. eriantha cv. 'White' being the earliest (22.9-45.7 mya) among that of the four Actinidia species. The 4DTv distance distribution highlighted three recent whole-genome duplication events in Acd. This is the first high-quality diploid Acd genome, which lays an important foundation for not only kiwifruit functional genomics studies but also further elucidating genome evolution of allohexaploid Acd.

Intercropping of Cyphomandra betacea with Different Ploidies of Solanum Sect. Solanum (Solanaceae) Wild Vegetables Increase Their Selenium Uptakes.

Selenium (Se) deficiency causes various diseases in humans. Se can be obtained from fruits and vegetables. In this study, the fruit tree Cyphomandra betacea was intercropped with three Solanum sect. Solanum (Solanaceae) wild vegetables [diploid (S. photeinocarpum), tetraploid (colchicine-induced S. photeinocarpum), and hexaploid (S. nigrum)], respectively, and Se uptakes of these plants were determined by a pot experiment. Intercropping decreased the biomass, photosynthetic pigment content, and superoxide dismutase activity of C. betacea, but increased the peroxidase (POD) activity, catalase (CAT) activity, and soluble protein content of C. betacea. These indicators' values of sect. Solanum increased after intercropping. The contents of Se increased in C. betacea and sect. Solanum after intercropping. Intercropped with diploid, tetraploid, and hexaploid increased the shoot Se contents in C. betacea by 13.73%, 17.49%, and 26.50%, respectively, relative to that of C. betacea monoculture. Intercropped with C. betacea increased the shoot Se contents in diploid, tetraploid, and hexaploid by 35.22%, 68.86%, and 74.46%, respectively, compared with their respective monoculture. The biomass and Se content of intercropped sect. Solanum showed linear relationships with the biomass and Se content of their monocultures. The biomass and Se content of intercropped C. betacea also exhibited linear relationships with that of sect. Solanum monocultures. Correlation and grey relational analyses revealed that the CAT activity, POD activity, and soluble protein content were the top three indicators closely associated with the C. betacea shoot Se content. The POD activity, soluble protein content, and translocation factor were the top three indicators closely associated with sect. Solanum shoot Se content. Therefore, intercropping can promote the Se uptake in C. betacea and sect. Solanum wild vegetables.

Dynamic Changes in Cell Wall Polysaccharides during Fruit Development and Ripening of Two Contrasting Loquat Cultivars and Associated Molecular Mechanisms.

Loquats have drawn much attention due to their essential nutrients and unusual phenology, which fills a market gap in early spring. Fruit firmness (FF) is one of the most important quality attributes. Dynamic changes in FF, cell wall (CW) polysaccharides, CW hydrolase activity, and expression of CW metabolism-related genes during the fruit development and ripening stages of two contrasting loquat cultivars were compared. Although the two cultivars possessed similar FF at the initial fruitlet stage, Dawuxing was significantly firmer than Ninghaibai at all subsequent time points. FF was positively correlated with the contents of covalent-soluble pectin and hemicellulose, activity of peroxidase, and gene expressions of PME, EG, CAD6, and POD; and negatively correlated with the contents of water-soluble pectin, activities of polygalacturonase, endo-glucanase, cellobiohydrolase, and xylanase, and gene expressions of PG, EG2, PAL1, PAL3, and CAD5. Identifying molecular mechanisms underlying the differences in FF is useful for fundamental research and crop improvement in future.

Identification of Key Genes Induced by Different Potassium Levels Provides Insight into the Formation of Fruit Quality in Grapes.

Inadequate potassium (K) availability is a common abiotic stress that limits the growth and quality of fruit trees. Few studies have investigated the physiological and molecular responses of grapes at different potassium levels. In this study, an integrated approach was developed for grapevines grown at four different potassium fertilization levels [0 (K0-CK), 150 (K150), 300 (K300), and 450 (K450) g/plant] in combination with metabolite measurements and transcript analysis. The results showed that different K levels affected the accumulation of sugars and anthocyanins in the fruit. At 78 days after bloom (DAB), the K150, K300, and K450 treatments increased soluble sugar content by 37.39%, 31.10% and 32.59%, respectively, and anthocyanin content by 49.78%, 24.10%, and 13.06%, respectively, compared to K0. Weighted gene co-expression network analysis (WGCNA) of DEGs identified a network of 11 grapevines involved. During fruit development, potassium application promoted the accumulation of anthocyanins and sugars in fruit by regulating the up-regulation of GST, AT, UFGT and SPS, HT, PK gene expressions. These results suggest that potassium deficiency inhibits anthocyanin and sugar metabolism. In addition, it promotes the up-regulation of KUP expression, which is the main cause of K accumulation in fruits. Together, our data revealed the molecular mechanism in response to different K levels during fruit quality formation and provides the scientific foundation for the improvement of fruit quality by adding K fertilizer.

Melatonin and arbuscular mycorrhizal fungi synergistically improve drought toleration in kiwifruit seedlings by increasing mycorrhizal colonization and nutrient uptake.

Kiwifruit is a vine fruit tree that is vulnerable to water deficiency due to its shallow root system and large leaves. Although mycorrhizal inoculation and melatonin application has been proved to improve plants drought tolerance, their interaction effects are still unclear. In this study, arbuscular mycorrhizal (AM) fungi incubation and melatonin (MT) irrigation were applied to kiwifruit seedlings alone or in combination to investigate their effect on drought tolerance. The results revealed that AM had more effect on promoting root biomass, water use efficiency, and uptake of nitrogen, phosphorus and iron. While MT was more effective in promoting shoot biomass and antioxidant enzyme activities to remove reactive oxygen species accumulation. Moreover, MT supplementary significantly increased the AM colonization, spore density and hyphal length density in roots. Therefore, combined application of AM fungi and MT had additive effects on improvement biomass accumulation, increasing chlorophyll content, photosynthetic efficiency, catalase activity, and decreasing malondialdehyde accumulation under drought stress, thus promoting plant growth and alleviating the drought damage to plant. These results provide guidance for AM and MT combined application to improve abiotic resistance in plants.

An amino acid fertilizer improves the emergent accumulator plant Nasturtium officinale R. Br. phytoremediation capability for cadmium-contaminated paddy soils.

Cadmium (Cd) contamination of paddy soil affects safe crop production. This study aimed to evaluate the effects of plant biostimulant amino acid fertilizer on the phytoremediation capability of an emergent accumulator plant Nasturtium officinale R. Br. for Cd-contaminated paddy soils. A pot study was carried out to study the effects of different concentrations of amino acid fertilizer on the Cd accumulation of N. officinale grown in Cd-contaminated paddy soil. The amino acid fertilizer increased the biomass of N. officinale. The amino acid fertilizer concentration exhibited a quadratic polynomial regression relationship with the root and shoot biomass. The fertilizer also increased the photosynthetic pigment (chlorophyll and carotenoid) contents, peroxidase (POD; EC 1.11.1.7) activity, and catalase (CAT; EC 1.11.1.6) activity of N. officinale, but decreased the soluble protein content and had no significant effect on the superoxide dismutase (SOD; EC 1.15.1.1) activity. Furthermore, the amino acid fertilizer increased the Cd content and Cd extraction of N. officinale. The shoot Cd extraction increased by 29.06%, 63.05%, 77.22%, and 17.40% at 1500-, 1200-, 900-, and 600-fold dilutions of the amino acid fertilizer, respectively, compared with the control. Moreover, the amino acid fertilizer promoted the Cd transport from the roots to shoots of N. officinale. The amino acid fertilizer concentration also exhibited a quadratic polynomial regression relationship with the root Cd content, shoot Cd content, root Cd extraction, and shoot Cd extraction, respectively. The correlation, grey relational, and path analyses revealed that the root biomass, shoot biomass, chlorophyll content, catalase activity, shoot Cd content, and root Cd extraction were closely associated with the shoot Cd extraction. Therefore, the amino acid fertilizer can promote Cd uptake and improve the phytoremediation capability of N. officinale to remediate Cd-contaminated paddy soils, and 900-fold dilution is the most suitable concentration.

Gibberellic acid promotes selenium accumulation in Cyphomandra betacea under selenium stress.

The selenium (Se) deficiency is threatening the human health, and the increase of Se content in food can prevent the Se deficiency of human body. To increase the Se content in fruit trees and alleviate the Se stress to fruit trees, the effects of gibberellic acid (GA) on the growth and Se accumulation in Cyphomandra betacea under Se stress were studied. Although GA increased the biomass of C. betacea, it did not significantly affect the root/shoot ratio. The root and shoot biomass had a quadratic polynomial regression relationship with the GA concentration. Furthermore, GA increased the photosynthetic pigment content, photosynthetic parameters, and antioxidant enzyme activity of C. betacea. GA also increased the Se content in C. betacea, peaking at 300 mg/L GA. For instance, GA (300 mg/L) increased the Se contents in roots and shoots of C. betacea by 70.31 and 22.02%, respectively, compared with the control. Moreover, the root Se and shoot Se contents had a quadratic polynomial regression relationship with the GA concentration. Correlation and gray relational analyses showed that the carotenoid, chlorophyll a, and chlorophyll b contents were closely related to the Se uptake in C. betacea under the GA application. These results show that GA (300 mg/L) can promote the growth and Se uptake of C. betacea under Se stress.