Water extract of Fagopyrum dibotrys (D. Don) Hara straw increases selenium accumulation in peach seedlings under selenium-contaminated soil.

To promote the selenium (Se) uptakes in fruit trees under Se-contaminated soil, the effects of water extract of Fagopyrum dibotrys (D. Don) Hara straw on the Se accumulation in peach seedlings under selenium-contaminated soil were studied. The results showed that the root biomass, chlorophyll content, activities of antioxidant enzymes, and soluble protein content of peach seedlings were increased by the F. dibotrys straw extract. The different forms of Se (total Se, inorganic Se, and organic Se) were also increased in peach seedlings following treatment with the F. dibotrys straw extract. The highest total shoot Se content was treated by the 300-fold dilution of F. dibotrys straw, which was 30.87% higher than the control. The F. dibotrys straw extract also increased the activities of adenosine triphosphate sulfurase (ATPS), and adenosine 5'-phosphosulfate reductase (APR) in peach seedlings, but decreased the activity of serine acetyltransferase (SAT). Additionally, correlation and grey relational analyses revealed that chlorophyll a content, APR activity, and root biomass were closely associated with the total shoot Se content. Overall, this study shows that the water extract of F. dibotrys straw can promote Se uptake in peach seedlings, and 300-fold dilution is the most suitable concentration.

The water extract of Fagopyrum dibotrys (D. Don) Hara straw promoted the selenium (Se) uptake in peach seedlings under selenium-contaminated soil. The concentration of F. dibotrys straw extract showed a quadratic polynomial regression relationship with the total root and shoot Se. Furthermore, chlorophyll a content, APR activity, and root biomass were closely associated with the total shoot Se. This study shows that water extract of F. dibotrys straw can promote Se uptake in peach seedlings, and 300-fold dilution is the most suitable concentration.

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.

Effects of mutual intercropping on cadmium accumulation of Solanum photeinocarpum Nakamura et Odashima and its post-grafting generations.

The cadmium (Cd) contaminated agricultural soil has become serious in recent years, but it will take long time for Cd-hyperaccumulator to remedy. To speed up the remediation of agricultural soil and achieve the safe agricultural production as soon as possible, the potential Cd-hyperaccumulator Solanum photeinocarpum Nakamura et Odashima was intercropped with its post-grafting generations in Cd-contaminated soil. Intercropping increased the biomass, Cd contents and Cd extractions of S. photeinocarpum and its post-grafting generations in the pot and field experiments. Both the whole plant or shoot biomass and the Cd extraction by whole plant or shoot in intercroppings had a linear regression relationship with that in monocultures. In the field experiment, intercropping increased the shoot Cd extraction of S. photeinocarpum by 9.86%-40.06% compared with the monoculture. Intercropping increased the content of chlorophyll, activity of superoxide dismutase, activity of catalase, and soluble protein content of S. photeinocarpum and its post-grafting generations but reduced their peroxidase activities in the pot experiment. Therefore, intercropping S. photeinocarpum with its post-grafting generations can improve their phytoremediation ability, and the best choice is S. photeinocarpum intercropped with its post-grafting generation of wild potato rootstock. Novelty statementIntercropping Solanum photeinocarpum Nakamura et Odashima with its post-grafting generations could mutually promote the Cd accumulation in the two types of plant species, and improve their phytoremediation ability for remedying the Cd-contaminated soil.

Effects of intercropping on Se accumulation and growth of pakchoi, lettuce and radish.

Selenium is one of the most basic trace elements in the human body. It is necessary to improve the selenium content in agricultural products through agricultural planting technology to ensure that human nutrition and health need selenium. Therefore, our research passed the effect of intercropping on the growth and selenium accumulation of pakchoi, lettuce and radish were studied through pot experiments to determine whether intercropping of the three crop species can improve their selenium accumulation ability. The results showed that intercropping increased the root and shoot biomass of pakchoi and radish compared with the monocultures, while the biomass of roots and shoots decreased in other intercropping combinations. Intercropping also affected the photosynthetic pigment content of the three crop species. Specifically, the photosynthetic pigments increased in pakchoi and decreased in radish after intercropping. Notably, intercropping the three crop species together increased the SOD (superoxide dismutase) activities of the three crops compared with the monocultures. Meanwhile, intercropping radish with lettuce significantly increased the activities of SOD and CAT (catalase) in radish. Intercropping also increased the soluble sugar content in pakchoi and soluble protein content of radish relative to the monocultures. Furthermore, intercropping decreased the selenium content and the bioconcentration factor of the roots of the three vegetable crops, but improved the shoot selenium content, the bioconcentration factor and the transport factor of Se in pakchoi and radish. In conclusion, intercropping combination of pakchoi and radish can improve selenium accumulation in the edible parts of the crops, which is significant for efficient production of selenium-enriched vegetables.

This research is significant because this study provides some basis for improving the selenium content of plants and efficient production of pakchoi and radish. Under the condition of selenium application in soil, the intercropping of pakchoi and lettuce can promote the growth of both and improve their selenium enrichment ability.

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.

Ultra-HPLC-MS pseudo-targeted metabolomic profiling reveals metabolites and associated metabolic pathway alterations in Asian plum (Prunus salicina) fruits in response to gummosis disease.

Plum (Prunus spp.) is an economically and nutritionally important stone fruit that is grown worldwide. Gummosis disease (GD) is one of the most common limiting factors that adversely affects the yield and quality of stone fruits such as plum. Elucidating plum fruit metabolomics responses is essential to develop sustainable agricultural practices to combat GD in the future. Herein, an ultra-high-performance liquid chromatography coupled to mass-spectrometry (UHPLC-MS) pseudo-targeted metabolomic profiling was first performed to elucidate the overall metabolic alterations in Asian plum (Prunus salicina Lindl.) fruit in response to GD. The most pivotal differential metabolites, including certain amino acids and proanthocyanidins, in GD and control groups were identified by combining multivariate data analysis with strict statistical criteria. Metabolic pathway enrichment analysis showed that GD induced a series of coordinated defence responses and reprogramming of various metabolic pathways, including glucosinolate biosynthesis, 2-oxocarboxylic acid metabolism, valine, leucine and isoleucine degradation, and isoquinoline alkaloid biosynthesis pathways. Using UHPLC-MS-based pseudo-targeted metabolomic profiling, we systematically evaluated overall metabolic modifications in Asian plum fruits in response to GD for the first time. The identified metabolic pathway alterations helped to better understand the internal relationships and related metabolic networks.

Effects of intercropping with Solanum photeinocarpum and its post-grafting generations on cadmium accumulation in loquat (Eriobotrya japonica).

Cadmium (Cd) contamination of orchard soils is a global problem that has been increasing. To decrease the Cd accumulation in fruits, intercropping the orchard crops with hyperaccumulator plants has been used for soil remediation. A pot and a field experiment were conducted to study the effects of intercropping the potential Cd-hyperaccumulator Solanum photeinocarpum and its post-grafting generations with loquat (Eriobotrya japonica) on the growth and Cd uptake of these two plant species. In the pot experiment, intercropping improved the biomass, Cd content, Cd extraction, and root-to-shoot Cd translocation in both species. Intercropping increased the DNA methylation levels, antioxidant enzyme activity, and soluble protein content of loquat seedlings. These results indicate that intercropping could improve the phytoremediation of S. photeinocarpum and its post-grafting generations and increase the Cd uptake in loquat seedlings. In the field experiment, intercropping increased the Cd contents in the old branches, while it decreased that in the young branches and fruits of loquat. These findings indicate that intercropping could increase the Cd uptake in old tissues but reduce the Cd uptake in young tissues and fruits of loquat. So, intercropping loquat with S. photeinocarpum and its post-grafting generations could be used in Cd-contaminated orchards.

Intercropping the potential Cd-hyperaccumulator Solanum photeinocarpum and its post-grafting generations with loquat mutually promoted the growth of two plant species, and also promoted the cadmium uptakes in S. photeinocarpum and old branches of loquat, while inhibited the Cd uptake in the loquat young tissues (young branches and fruits). These results are the new findings of the intercropping.

Intercropping with post-grafting generation of Solanum photeinocarpum decreases cadmium accumulation in soybean (Glycine max).

A pot experiment was designed to explore the effects of different post-grafting generations of Solanum photeinocarpum Nakamura et Odashima intercropping on growth and cadmium (Cd) accumulation in soybeans (varieties: "Zaodou" and "Liaoxian"). Post generation of S. photeinocarpum (ungrafted, grafted on eggplant, potato, and tomato, respectively) were utilized to intercrop with two varieties of soybean in Cd-contaminated soil. Soybean monoculture was employed as a control. Consequently, intercropping with different post-grafting S. photeinocarpum generation, except for tomato rootstock grafts post-generation, could reduce soybean biomass and photosynthetic pigment content. Additionally, all S. photeinocarpum post-grafting generations had the capacity to reduce Cd content in soybean when intercropping, while tomato rootstock grafts post-generation exhibited an adequate ability to accumulate Cd in S. photeinocarpum compared to the ungrafted treatment. In particular, tomato rootstock grafts post-generation could effectively decrease Cd content in soybean organs by 14.09-62.13%, relative to soybean monoculture, but increased shoot Cd content and shoot Cd extraction of S. photeinocarpum by 10.33-13.49% and 10.38-12.03%, respectively, compared to the ungrafted treatment. Thus, tomato rootstock grafting may enhance the ability of post-grafting generation of S. photeinocarpum to remediate Cd-contaminated soil, and this grafting was able to reduce Cd accumulation in soybean.

Mowing enhances the phytoremediation ability of cadmium-contaminated soil in the post-grafting generations of potential cadmium-hyperaccumulator Solanum photeinocarpum.

The study aimed at accessing the effects of mowing on the growth and cadmium (Cd) accumulation of the first post-grafting generation of potential Cd-hyperaccumulator plant Solanum photeinocarpum through the pot and plot experiments. Four grafting treatments were employed such as ungrafted (UG), self-rooted grafting by the same S. photeinocarpum seedling (SG), self-rooted grafting by two different development stages of S. photeinocarpum seedlings (DG), and grafting on the rootstock of wild potato (PG). The biomass, Cd content, and Cd extraction amount of S. photeinocarpum shoots significantly decreased with the increase of mowing times in the pot and plot experiments. The order of the grafting on the biomass, Cd content, and Cd extraction amountof in the first, second, third mowing shoots were PG > DG > SG > UG. For the Cd extraction amountof total moving shoots, SG, DG, and PG increased by 20.42%, 35.54%, and 52.94%, respectively, in the pot experiment, and increased by 11.56%, 26.28%, and 44.90%, respectively, in the plot experiment, compared with the UG. Therefore, mowing provides an insight into the phytoremediation ability of S. photeinocarpum to Cd.

Effects of reciprocal grafting on cadmium accumulation in post-grafting generations of two ecotypes of Solanum photeinocarpum.

Farmland and mining ecotypes of the potential cadmium (Cd)-hyperaccumulator Solanum photeinocarpum were collected to study the effects of reciprocal grafting on the growth of, and Cd accumulation in, the post-grafting generations. The post generations of the following plant materials were evaluated in a pot experiment: the un-grafted farmland ecotype, grafted plants with the farmland ecotype as the scion or the rootstock, the un-grafted mining ecotype, and grafted plants with the mining ecotype as the scion or the rootstock. The results showed that reciprocal grafting increased the biomass, the activities of superoxide dismutase, peroxidase, and catalase, and the soluble protein content in the post-grafting generations of both ecotypes S. photeinocarpum. Reciprocal grafting also increased the Cd content in, and amount of Cd extracted by, the post-grafting generations of both ecotypes S. photeinocarpum as a result of lower soil pH and higher soil available Cd concentrations. Additionally, grafting affected the DNA methylation levels by inducing hypermethylation or demethylation in the post-grafting generation. Therefore, reciprocal grafting can enhance the Cd accumulation (phytoremediation) capacity of post-grafting generations of both ecotypes S. photeinocarpum by affecting DNA methylation levels.

Effects of intercropping with two Solanum species on the growth and cadmium accumulation of Cyphomandra betacea seedlings.

The contamination of orchard by cadmium (Cd) has recently increased in severity. To decrease the Cd content in fruit tree, a pot-based experiment was conducted to study the effects of intercropping with two Solanum species (Solanum alatum and Solanum diphyllum) on the growth and Cd accumulation of Cyphomandra betacea seedlings. The data revealed that intercropping with two Solanum species significantly increased the biomass, photosynthetic pigment contents, antioxidant enzyme activities, and soluble protein contents of C. betacea seedlings under Cd stress condition. The intercropping significantly decreased the Cd content in C. betacea seedlings. However, the intercropping significantly decreased the S. alatum and S. diphyllum biomasses, while increased the Cd content and accumulation in the roots and shoots of two Solanum species, and the Cd uptake by S. alatum was lower than that of S. diphyllum. Therefore, intercropping with these two Solanum species, especially S. diphyllum, may promote the growth and decrease the Cd content in C. betacea.

Effects of reciprocal hybridization on cadmium accumulation in F1 hybrids of two Solanum photeinocarpum ecotypes.

In this study, farmland and mining ecotypes of Solanum photeinocarpum (a potential cadmium (Cd) hyperaccumulator plant) were reciprocally hybridized each other, and the Cd accumulation characteristics of the F1 hybrids were studied. In pot experiments, higher biomasses and Cd extraction abilities were found for two S. photeinocarpum F1 hybrids than for the parents, but the Cd contents in various organs were lower in the hybrids than the parents. However, the differences between the Cd contents in the two hybrids were not significant. The antioxidant enzyme (superoxide dismutase and peroxidase) activities were higher for the S. photeinocarpum F1 hybrids than the parents. Less DNA methylation was found in the hybrids than the parents because more demethylation occurred in the hybrids than the parents. The biomass, Cd content, and Cd extraction ability effects in field experiments were similar to the effects in the pot experiments. It was concluded that reciprocally hybridizing different S. photeinocarpum ecotypes improved the ability of S. photeinocarpum to be used to phytoremediate contaminated land.

SUNRED, a natural extract-based biostimulant, application stimulates anthocyanin production in the skins of grapes.

Anthocyanins are important components in skins of red table grapes and contribute to the berries appearance, a key quality characteristic for customers. In recent years, exogenous foliage fertilizers has been applied to grapevines to improve the pigmentation of the fruit. The present study examines the effect on a biostimulant (SUNRED) pre-véraison application in the accumulation of anthocyanins in 'Red Globe' grapes, and investigates the related changes in expression of key genes and their enzyme activities in the flavonoid pathways. Additionally, abscisic acid (S-ABA) was also applied to grapevines to evaluate the comparative effect of SUNRED. Our analyses showed that total anthocyanin contents increased in both SUNRED and S-ABA treated grapes; for S-ABA, a 1% dilution (A100) of the commercially available stock solution treatments represented the greatest effect on pigmentation; for SUNRED, a 0.1% dilution (S1000) was most effective. The anthocyanin contents increased by 1.16-fold and 1.4-fold after A100 and S1000 treatments, respectively. The gene expression analyses showed that almost all genes involved in the anthocyanin biosynthesis pathway up-regulated after A100 and S1000 treatments, suggesting that the increment in total anthocyanin content was attributed to the increased expression level of related genes. Moreover, the activities of phenylalanine ammonia-lyase (PAL), chalcone isomerase (CHI), UDP glucose: flavonoid 3-o-glucosyl transferase (UFGT) and dihydroflavonol 4-reductase (DFR), key enzymes for biosynthesis of anthocyanin, were increased by the exogenous treatments. Overall, our findings clearly demonstrate that application of exogenous biostimulant have a positive effect on the pigment characteristics of grape crop.

Effects of mutual grafting on the cadmium accumulation characteristics of two ecotypes of Solanum photeinocarpum.

The effects of mutual grafting on the cadmium (Cd) accumulation characteristics of two ecotypes (farmland and mining) of the potential Cd-hyperaccumulator Solanum photeinocarpum were studied through a pot experiment for one month. Four treatments were used in the experiment: ungrafted farmland ecotype (F-CK), ungrafted mining ecotype (M-CK), the farmland ecotype as the scion grafted onto rootstocks of the mining ecotype (F-Scion), and the mining ecotype as the scion grafted onto rootstocks of the farmland ecotype (M-Scion). Mutual grafting increased the rootstock biomass of both S. photeinocarpum ecotypes. However, mutual grafting decreased the scion biomass of F-Scion compared with F-CK and M-CK, and the scion biomass of M-Scion was higher than that of M-CK and lower than that of F-CK. The Cd content in the rootstock of M-Scion increased compared with F-CK, and the Cd content in the rootstock of F-Scion increased compared with M-CK, but mutual grafting decreased the Cd content in scions of both S. photeinocarpum ecotypes. Mutual grafting increased Cd extraction by rootstocks of both S. photeinocarpum ecotypes, but decreased extraction by scions. Therefore, mutual grafting can increase Cd accumulation in S. photeinocarpum rootstocks but not increase Cd accumulation in S. photeinocarpum scions in a short period.

Cadmium-accumulator straw application alleviates cadmium stress of lettuce (Lactuca sativa) by promoting photosynthetic activity and antioxidative enzyme activities.

The effects of application of straw derived from cadmium (Cd) accumulator plants (Siegesbeckia orientalis, Conyza canadensis, Eclipta prostrata, and Solanum photeinocarpum) on growth and Cd accumulation of lettuce plants grown under Cd exposure were studied. Treatment with straw of the four Cd-accumulator species promoted growth, photosynthesis, and soluble protein contents and enhanced the activities of peroxidase in leaves of lettuce seedlings. The biomass of shoot of lettuce from high to low in turn is the treatment of C. canadensis straw > S. photeinocarpum straw > S. orientalis > E. prostrata > Control. The Cd content in edible parts (shoots) of the lettuce plants was significantly decreased in the presence of straw from the Cd-accumulator species, except the presence of the straw of E. prostrata. And, the greatest reduction in Cd content in shoots was 27.09% in the S. photeinocarpum straw treatment compared with that of the control. Therefore, application of straw of S. orientalis, C. canadensis, and S. photeinocarpum can promote the growth of lettuce seedlings, and decrease their Cd accumulation, when grown in Cd-contaminated soil, which is beneficial for production of lettuce safe for human consumption.

Transcriptomic insights into citrus segment membrane's cell wall components relating to fruit sensory texture.

BACKGROUND: During fresh fruit consumption, sensory texture is one factor that affects the organoleptic qualities. Chemical components of plant cell walls, including pectin, cellulose, hemicellulose and lignin, play central roles in determining the textural qualities. To explore the genes and regulatory pathways involved in fresh citrus' perceived sensory texture, we performed mRNA-seq analyses of the segment membranes of two citrus cultivars, Shiranui and Kiyomi, with different organoleptic textures. RESULTS: Segment membranes were sampled at two developmental stages of citrus fruit, the beginning and end of the expansion period. More than 3000 differentially expressed genes were identified. The gene ontology analysis revealed that more categories were significantly enriched in 'Shiranui' than in 'Kiyomi' at both developmental stages. In total, 108 significantly enriched pathways were obtained, with most belonging to metabolism. A detailed transcriptomic analysis revealed potential critical genes involved in the metabolism of cell wall structures, for example, GAUT4 in pectin synthesis, CESA1, 3 and 6, and SUS4 in cellulose synthesis, CSLC5, XXT1 and XXT2 in hemicellulose synthesis, and CSE in lignin synthesis. Low levels, or no expression, of genes involved in cellulose and hemicellulose, such as CESA4, CESA7, CESA8, IRX9 and IRX14, confirmed that secondary cell walls were negligible or absent in citrus segment membranes. A chemical component analysis of the segment membranes from mature fruit revealed that the pectin, cellulose and lignin contents, and the segment membrane's weight (% of segment) were greater in 'Kiyomi'. CONCLUSION: Organoleptic quality of citrus is easily overlooked. It is mainly determined by sensory texture perceived in citrus segment membrane properties. We performed mRNA-seq analyses of citrus segment membranes to explore the genes and regulatory pathways involved in fresh citrus' perceived sensory texture. Transcriptomic data showed high repeatability between two independent biological replicates. The expression levels of genes involved in cell wall structure metabolism, including pectin, cellulose, hemicellulose and lignin, were investigated. Meanwhile, chemical component contents of the segment membranes from mature fruit were analyzed. This study provided detailed transcriptional regulatory profiles of different organoleptic citrus qualities and integrated insights into the mechanisms affecting citrus' sensory texture.

Effects of melatonin on the growth and cadmium characteristics of Cyphomandra betacea seedlings.

To determine whether the melatonin (MT) could reduce cadmium (Cd) accumulation in Cyphomandra betacea seedlings, different concentrations of MT were added to the nutrient solution and soil to study its effects on the growth and Cd characteristics of C. betacea seedlings. Fifty micromoles per liter (µmol/kg) of MT increased the biomass of C. betacea seedlings, but 100-200 µmol/L (µmol/kg) MT decreased seedling biomass in both the nutrient solution and soil cultivation experiments. The photosynthetic pigment contents showed no significant changes compared with the control when the MT dose was 150 µmol/L (µmol/kg) or less, while 200 µmol/L (µmol/kg) MT decreased the photosynthetic pigment contents. Low levels of MT improved the antioxidant enzyme activities of C. betacea seedlings, whereas high MT levels reduced them. MT increased the Cd contents in different organs of C. betacea seedlings in the nutrient solution cultivation experiment, but only 50 µmol/kg MT increased the Cd contents in stems, leaves, and shoots of C. betacea seedlings in the soil cultivation experiment. Therefore, only low levels of MT can promote the growth of C. betacea seedlings, and MT is not suitable for reducing Cd accumulation in C. betacea seedlings.

Addition of straw from hyperaccumulator plants to cadmium-contaminated soil increases cadmium uptake by loquat seedlings.

The straw from three different cadmium (Cd) hyperaccumulators (Galinsoga parviflora, Youngia erythrocarpa, and Solanum photeinocarpum) was added to Cd-contaminated soil, and its effects on plant growth and Cd accumulation in loquat seedlings were evaluated. Straw from each of G. parviflora, Y. erythrocarpa, and S. photeinocarpum was added to Cd-contaminated soil before planting seedlings of two varieties of loquat (Dawuxing and Chuanzao). Addition of straw from G. parviflora and S. photeinocarpum increased the root and shoot biomasses of both loquat varieties, compared with that in the control. Addition of straw also increased Cd uptake by loquat seedlings. The treatments could be ranked, from highest Cd contents in roots and shoots of loquat seedlings to lowest, as follows: S. photeinocarpum straw > Y. erythrocarpa straw > G. parviflora straw > control. All three types of hyperaccumulator straw increased the amount of Cd extracted by shoots of two loquat seedlings, with the maximum effect in the S. photeinocarpum straw treatment. Addition of hyperaccumulator straw also resulted in increased soil invertase, urease, and catalase activities to varying degrees. Among the three types of hyperaccumulator straw, S. photeinocarpum straw was the most effective to increase Cd accumulation in loquat seedlings. Therefore, this material has the potential to increase the phytoremediation capacity of loquat seedlings in Cd-contaminated orchards.

Ascorbic acid metabolism during sweet cherry (Prunus avium) fruit development.

To elucidate metabolism of ascorbic acid (AsA) in sweet cherry fruit (Prunus avium 'Hongdeng'), we quantified AsA concentration, cloned sequences involved in AsA metabolism and investigated their mRNA expression levels, and determined the activity levels of selected enzymes during fruit development and maturation. We found that AsA concentration was highest at the petal-fall period (0 days after anthesis) and decreased progressively during ripening, but with a slight increase at maturity. AsA did nevertheless continue to accumulate over time because of the increase in fruit fresh weight. Full-length cDNAs of 10 genes involved in the L-galactose pathway of AsA biosynthesis and 10 involved in recycling were obtained. Gene expression patterns of GDP-L-galactose phosphorylase (GGP2), L-galactono-1, 4-lactone dehydrogenase (GalLDH), ascorbate peroxidase (APX3), ascorbate oxidase (AO2), glutathione reductase (GR1), and dehydroascorbate reductase (DHAR1) were in accordance with the AsA concentration pattern during fruit development, indicating that genes involved in ascorbic acid biosynthesis, degradation, and recycling worked in concert to regulate ascorbic acid accumulation in sweet cherry fruit.