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Abscisic acid (ABA) is an important hormone that can regulate the heavy-metal uptake of plants. In this study, exogenous ABA was applied to lettuce (Lactuca sativa) grown under cadmium (Cd)-stress conditions, and the effects of exogenous ABA on the growth and Cd accumulation of lettuce were evaluated. The results showed that treatment of Cd significantly decreased biomass and increased Cd content of lettuce compared with the control. The shoot biomass increased after spraying 1, 5 and 10 μmol/L ABA, and the root biomass increased after spraying 1–20 μmol/L ABA compared with the treatment of Cd. The Cd content in shoots significantly decreased when exposed to different ABA concentrations. The lowest Cd content in shoots of lettuce was produced by the ABA concentration of 5 μmol/L, with decreased by 23.60% compared with the treatment of Cd. Therefore, spraying ABA effectively alleviated Cd toxicity and reduced Cd uptake in the edible parts of lettuce, and 5 μmol/L ABA was the optimal dose. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to study the effects of intercropping with the cadmium (Cd) hyperaccumulators Galinsoga parviflora, Bidens pilosa, Cosmos sulphureus and Solanum nigrum on the growth and Cd accumulation of water spinach (Ipomoea aquatica Forsk). The results show that intercropping with B. pilosa improved biomass and photosynthetic pigment contents of water spinach, but intercropping with G. parviflora, C. sulphureus and S. nigrum shaded water spinach; thus, the growth of water spinach was inhibited. When compared with monoculture, the Cd contents in roots and shoots of water spinach were reduced by intercropping with B. pilosa, C. sulphureus and S. nigrum, and the shoot Cd content decreased by 27.93%, 3.12% and 5.30%, respectively. Intercropping with G. parviflora reduced the root Cd content in water spinach, but increased the shoot Cd content. Therefore, intercropping with B. pilosa could promote the growth and reduce the Cd accumulation of water spinach. [ABSTRACT FROM AUTHOR]

In this study, pot experiments were conducted to study the effects of reciprocal grafting on the growth and Cd accumulation in post-grafting generations of two cherry tomatoes – red (Red cherry 5-5-1-1) and yellow (RTY-3-2) cherry tomatoes. Six treatments, which consisted of ungrafted red cherry tomato (R-CK), ungrafted yellow cherry tomato (Y-CK), red cherry tomato as rootstock (R-rootstock), red cherry tomato as scion (R-scion), yellow cherry tomato as rootstock (Y- rootstock), and yellow cherry tomato as scion (Y-scion) were utilised. The results showed that grafting significantly decreased the root biomass of Y- rootstock and Y-scion as compared to that of Y-CK, but there were no differences in the shoot biomass. Compared with that of Y-CK, grafting increased the root Cd content of the post-grafting generations, specifically, Y- rootstock and Y-scion increased by 54.44% and 52.96%, respectively. There were no significant differences in the shoot Cd content of Y- rootstock, Y-scion, and Y-CK. The root, stem, leaf, and shoot biomass of R-rootstock increased by 14.17%, 76.23%, 36.47%, and 21.72%, respectively, as compared with that of R-CK. However, grafting had no significant effect on the root, stem, leaf, and shoot biomass of R-scion. Grafting significantly increased the root Cd content of R-rootstock. However, grafting significantly decreased the shoot Cd content of R-rootstock, with the value 26.18% lower than that of R-CK. The root Cd content of R-scion significantly increased compared with the R-CK, and the shoot Cd content had no differences. Therefore, the reciprocal grafting of the two cherry tomatoes promoted the growth and reduced the Cd uptake of R-rootstock. Findings from this study could be used to provide a reference for the safe production of tomatoes in heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effects of spraying an algal biostimulant at different concentrations (0, 600-, 900-, 1200-, and 1500-fold dilutions) on the growth and cadmium (Cd) accumulation characteristics of accumulator plant Nasturtium officinale. In a pot experiment, application of the algal biostimulant at all concentrations promoted the growth of N. officinale by increasing the root and shoot biomasses, and the 600-fold dilution of the algal biostimulant had the strongest effect. At all concentrations, the algal biostimulant had no significant effect on the Cd content in roots of N. officinale, and increased the Cd extraction by roots. However, all concentrations of the algal biostimulant except for the 1500-fold dilution decreased the Cd content in shoots and Cd extraction by shoots. The N. officinale plants treated with the 600-fold dilution of the algal biostimulant had the lowest shoot Cd contents and Cd extraction by shoots. The algal biostimulant also increased the contents of photosynthetic pigments (chlorophyll a, total chlorophyll, and carotenoids) in leaves of N. officinale to varying degrees. Different concentrations of algal biostimulant reduced the superoxide dismutase activity, peroxidase activity, and malondialdehyde content of N. officinale, but enhanced the catalase activity, soluble protein content, and relative conductivity. Overall, the 600-fold dilution had the strongest effect on the growth and Cd accumulation characteristics of N. officinale, but did not enhance the phytoremediation ability of N. officinale for growth in Cd-contaminated soil. These results show that this algal biostimulant can promote the growth and reduce the Cd uptake of N. officinale, which is benefit for N. officinale safety production as a wild vegetable in Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Cuttings are asexual reproduction, and different vegetative organs of the plant can be selected as cuttings to grow into a new plant. Growth and cadmium (Cd) accumulation of cuttings taken from tomato (Solanum lycopersicum) plants non-grafted or grafted onto five different rootstocks were studied in a pot experiment. 'Zhongyanhong 6ʹ and 'Hongyu F1ʹ were non-grafted (CK) and were grafted onto Solanum torvum, Totosga, 'Dalishengen', 'Banzhen 18ʹ and 'Guozhen 1ʹ, respectively, planted in pots without Cd-contaminated soil. Cuttings were taken after one month, then grown in Cd-contaminated soil (10 mg kg−1) for three months. In 'Zhongyanhong 6ʹ cuttings, compared with non-grafted, grafting onto five rootstocks increased plant dry weight, grafting onto 'Banzhen 18ʹ and S. torvum increased plant height, grafting onto 'Banzhen 18ʹ and 'Guozhen 1' increased fruit fresh weight, grafting onto 'Guozhen 1ʹ and 'Dalishengen' reduced Cd content in fruit. In 'Hongyu F1ʹ cuttings, compared with non-grafted, grafting onto five rootstocks increased plant dry weight, grafting onto Totosga increased plant height, grafting onto S. torvum and Totosga increased fruit fresh weight, grafting onto 'Banzhen 18ʹ, 'Dalishengen', S. torvum and Totosga decreased Cd content in fruit. Cutting after grafting affects growth and Cd accumulation of tomato, which can provide a theoretical basis for the safe production of nightshade vegetables. [ABSTRACT FROM AUTHOR]

To identify whether the auxin treatment could promote the growth and reduce the cadmium (Cd) of fruit trees, the effects of different concentrations of indole acetic acid (IAA, one of the auxin) on the biomass, Cd content, photosynthetic pigment content, photosynthetic characteristics, antioxidant enzyme activity, and soluble sugars content in Cyphomandra betacea seedlings under Cd stress were studied. As the IAA concentration increased, the biomass, photosynthetic pigment content, soluble sugars content, and net photosynthetic rate of C. betacea seedlings tended to first increase and then decrease, with maximum values in the 60 mg/L IAA treatment. The Cd contents in different organs decreased and then increased with increasing IAA concentrations, with the minimum value in the 60 mg/L IAA treatment. Compared with the control, IAA treatments enhanced the activities of peroxidase and superoxide dismutase in the leaves of C. betacea seedlings and decreased the soluble protein content. Therefore, IAA treatments promoted growth, enhanced Cd resistance, and decreased the Cd content in C. betacea. The 60 mg/L IAA treatment was the most effective for promoting growth and decreasing the Cd content in C. betacea. [ABSTRACT FROM AUTHOR]

Straw of Solanum photeinocarpum accessions originating from two climatic-ecological zones (Chengdu, in the Mountain-Central Subtropical-Cold Zone; and Ya'an, in the Central Subtropical-Long Spring and Summer-Drought Zone) and their reciprocal F1 hybrids were added to Cd-contaminated soil, and their effects on the growth and Cd accumulation of lettuce were evaluated. Addition of S. photeinocarpum straw significantly increased biomass and decreased Cd content of lettuce, especially the straw of F1 hybrids raised from a Chengdu pollen donor. Shoot biomass was increased by 26.87%and the shoot Cd content was decreased by 25.86% compared with those of the control. The chlorophyll content and net photosynthetic rate were increased in response to the addition of S. photeinocarpum straw, and the effects of straw of reciprocal F1 hybrids were superior to those of the parents. Application of S. photeinocarpum straw promoted osmoticas (soluble sugar, soluble protein, free proline) contents and activities of antioxidant enzymes [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT)], reduced malondialdehyde (MDA) accumulation, and thus effectively improved the resistance of lettuce to Cd stress. S. photeinocarpum straw increased soil pH and organic matter content, and consequently decreased soil exchangeable Cd content, the strongest effect was achieved by application of S. photeinocarpum straw of reciprocal F1 hybrids raised from a Chengdu pollen donor, in response to which the soil exchangeable Cd content was decreased by 29.62% compared with that of the control. Therefore, the application of S. photeinocarpum straw in Cd-contaminated soil promoted growth and reduced the risk of Cd contamination of lettuce plants. The effects of straw from reciprocal F1 hybrids derived from a Chengdu pollen donor were superior to those of straw from the parents, and thus may be effectively used to improve the safe production of lettuce in Cd-contaminated soil. [ABSTRACT FROM AUTHOR]

Two pot experiments were conducted to study the effects of intercropping with cadmium (Cd) accumulator plant Eclipta prostrata and hyperaccumulator plant Crassocephalum crepidioides on the growth and Cd accumulation of tomato seedlings. In the preliminary experiment, intercropping with E. prostrata and C. crepidioides promoted the growth and decreased the Cd content in roots and shoots of tomato seedlings. In the further experiment, intercropping with E. prostrata and C. crepidioides had the same effects on the growth and Cd content of tomato seedlings as the preliminary experiment. In the further experiment, when three plant species (E. prostrate, C. crepidioides and tomato) intercropping together, the root and shoot biomasses of tomato seedlings got the maximum, and the Cd content in tomato seedlings got the minimum. Compared with the monoculture of tomato, three plant species intercropping increased the root and shoot biomasses of tomato seedlings by 49.28% and 64.19%, respectively, and decreased the Cd contents in roots and shoots of tomato seedlings by 17.35% and 22.35%, respectively. Intercropping with E. prostrata and C. crepidioides also increased the photosynthetic pigment content and enhanced the antioxidant enzyme activity of tomato seedlings. For accumulator and hyperaccumulator plants, intercropping with tomato inhibited the growth of E. prostrata and C. crepidioides, while increased the Cd content in two plant species. Therefore, intercropping with E. prostrata and C. crepidioides could promote the growth and reduce the Cd uptake of tomato seedlings, and three plant species intercropping together was the best combination. [ABSTRACT FROM AUTHOR]

To study the cadmium (Cd)-accumulation characteristics of the post-grafting generation of Cyphomandra betacea (Cav.) Sendt., the seeds of C. betacea grafted on Solanum nigrum L., tomato, and eggplant rootstocks were collected and planted in Cd-contaminated soil. Compared with seeds of ungrafted seedlings, the S. nigrum rootstock increased the shoot biomass of the post-grafting generation of C. betacea seedlings, while eggplant and tomato rootstocks decreased or had no significant effects. Only the S. nigrum rootstock increased the chlorophyll a content, net photosynthetic rate, and stomatal conductance of the post-grafting generation of C. betacea seedlings, while the other rootstocks decreased or had no significant effects on these photosynthetic parameters. The S. nigrum rootstock enhanced the superoxide dismutase and catalase activities, and soluble protein content, of the post-grafting generation of C. betacea seedlings, while the other rootstocks reduced or had no significant effects on these parameters. The three rootstocks decreased the Cd contents in different organs of the post-grafting generation of C. betacea seedlings, and the order of treatments was ungrafted > tomato rootstock > eggplant rootstock > S. nigrum rootstock. Therefore, S. nigrum was the best rootstock to promote the growth and decrease the Cd contents in post-grafting generation of C. betacea, and this can benefit C. betacea production in Cd-contaminated areas. [ABSTRACT FROM AUTHOR]

To study the effects of hyperaccumulator straw application on the growth and cadmium (Cd) accumulation of accumulator Perilla frutescens, four hyperaccumulator plant straws (Youngia erythrocarpa, Galinsoga parviflora, Gnaphalium affine and Crassocephalum crepidioides) were mulched on the surface of a Cd-contaminated soil (10 mg/kg) and P. frutescens seedlings were planted. The Y. erythrocarpa, G. affine and C. crepidioides straws increased P. frutescens root and shoot biomasses, and its chlorophyll a, carotenoid and total chlorophyll contents, whereas G. parviflora decreased or had no significant effect on these parameters. The G. affine and C. crepidioides straws enhanced the superoxide dismutase and catalase activities, and increased the Cd contents in roots and shoots of P. frutescens, whereas Y. erythrocarpa and G. parviflora straws had a smaller increasing effect. The Y. erythrocarpa, G. affine and C. crepidioides straws increased Cd extraction by P. frutescens shoots by 13.44%, 51.96% and 55.67%, respectively, compared with the control, whereas G. parviflora straw decreased it. Therefore, mulching with Y. erythrocarpa, G. affine and C. crepidioides straws could promote P. frutescens growth and enhance its phytoremediation ability for Cd-contaminated soil, with a better effect for G. affine and C. crepidioides straws than Y. erythrocarpa straw. [ABSTRACT FROM AUTHOR]

To study whether grafting can reduce the heavy metal uptake of Cyphomandra betacea, C. betacea seedlings were grafted onto three different rootstocks (eggplant, Solanum nigrum, and tomato) and planted in cadmium (Cd)contaminated soil. Compared with ungrafted seedlings, S. nigrum rootstock increased the biomass of different organs of C. betacea seedlings, while eggplant and tomato rootstocks decreased it or had no significant effect. Chlorophyll a, chlorophyll b, and total chlorophyll contents of C. betacea seedlings were ranked as follows: S. nigrum rootstock > ungrafted > eggplant rootstock > tomato rootstock. The three rootstocks had no significant effects on the superoxide dismutase activity of C. betacea seedlings. Solanum nigrum rootstock enhanced the peroxidase and catalase activities and soluble protein content of C. betacea seedlings, while the other rootstocks reduced or had no significant influence on these parameters. The three rootstocks increased the Cd content of aboveground organs of C. betacea seedlings as follows: S. nigrum rootstock > eggplant rootstock > tomato rootstock > ungrafted. Grafting onto S. nigrum rootstock can therefore promote the growth of C. betacea; however, all rootstocks investigated in this study promote Cd uptake in C. betacea and thus cannot be used in Cd-contaminated areas. [ABSTRACT FROM AUTHOR]