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The effect of elevated [CO2] on the growth of tomato plants with reduced gibberellin content is influenced by developmental stage. The impact of increased atmospheric carbon dioxide (CO2) on plants has aroused interest in the last decades. Signaling molecules known as plant hormones are fundamental controllers of plant growth and development. Elevated CO2 concentration ([CO2]) increases plant growth; however, whether plant hormones act as mediators of this effect is still an open question. Here, we show the response to elevated [CO2] in tomato does not require a functional gibberellin (GA) biosynthesis pathway. We compared growth and primary metabolism between wild-type (WT) and GA-deficient mutant (gib-1) plants transferred from ambient (400 ppm) to elevated (750 ppm) [CO2] at two different growth stages (either 21 or 35 days after germination, DAG). Growth, photosynthetic parameters and primary metabolism in the stunted gib-1 plants were restored when they were transferred to elevated [CO2] at 21 DAG. Elevated [CO2] also stimulated growth and photosynthetic parameters in WT plants at 21 DAG; however, only minor changes were observed in the level of primary metabolites. At 35 DAG, on the other hand, elevated [CO2] did not stimulate growth in WT plants and gib-1 mutants showed their characteristic stunted growth phenotype. Taken together, our results reveal that elevated [CO2] enhances growth only within a narrow developmental window, in which GA biosynthesis is dispensable. This finding could be relevant for breeding crops in the face of the expected increases in atmospheric CO2 over the next century.

Made available in DSpace on 2021-06-25T10:16:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Plants exposed to suboptimal temperatures suffer damage to physiological processes, growth, development and yield. Acting as enhancers of physiological and metabolic performance of plants, biostimulants have been used to mitigate crop damage caused by abiotic stresses. This study aimed to determine which formulation and dosage of FH Attivus® biostimulant have the best effects on the development of bean plants exposed to suboptimal temperatures (

Although boron (B) is an element that has long been assumed to be an essential plant micronutrient, this assumption has been recently questioned. Cumulative evidence has demonstrated that the players associated with B uptake and translocation by plant roots include a sophisticated set of proteins used to cope with B levels in the soil solution. Here, we summarize compelling evidence supporting the essential role of B in mediating plant developmental programs. Overall, most plant species studied to date have exhibited specific B transporters with tight genetic coordination in response to B levels in the soil. These transporters can uptake B from the soil, which is a highly uncommon occurrence for toxic elements. Moreover, the current tools available to determine B levels cannot precisely determine B translocation dynamics. We posit that B plays a key role in plant metabolic activities. Its importance in the regulation of development of the root and shoot meristem is associated with plant developmental phase transitions, which are crucial processes in the completion of their life cycle. We provide further evidence that plants need to acquire sufficient amounts of B while protecting themselves from its toxic effects. Thus, the development of in vitro and in vivo approaches is required to accurately determine B levels, and subsequently, to define unambiguously the function of B in terrestrial plants.

Made available in DSpace on 2021-06-25T10:16:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) To meet the growing demand for soybean it is necessary to increase crop yield, even in low water availability conditions. To circumvent the negative effects of water deficit, application of biostimulants with anti-stress effect has been adopted, including products based on fulvic acids and Ascophyllum nodosum (L.) seaweed extracts. In this study, we determined which formulation and dosage of a biostimulant is more efficient in promoting the recovery of soybean plants after stress due to water deficit. The experiment was conducted in a greenhouse, in a double-factorial randomized block design with two additional factors, four repetitions and eleven treatments consisting of three biostimulant formulations (F1, F2 and F3), and three dosages (0.25; 0.50 and 1.0 kg ha−1); a control with water deficit and a control without water deficit. Soybean plants were kept at 50% of the pot's water capacity for three days, then rehydrated and submitted to the application of treatments with biostimulant. After two days of recovery, growth, physiological, biochemical and yield parameters were evaluated. All plants that received the application of the biostimulant produced more than the water-stressed control plants. The biostimulant provided higher photosynthetic rates, more efficient mechanisms for dissipating excess energy and higher activities of antioxidant enzymes. Plants treated with biostimulant were more efficient in the recovery of the metabolic activities after rewatering, resulting in increased soybean tolerance to water deficit and reduced yield losses. The best result obtained was through the application of formulation 2 of the biostimulant at a dosage of 0.25 kg ha−1. Laboratory of Ecophysiology Applied to Agriculture School of Agricultural Sciences São Paulo State University (UNESP) Laboratory of Ecophysiology and Crop Production Federal Goianian Institute (IF Goiano), Campus Rio Verde Fertilizers Heringer Laboratory of Ecophysiology Applied to Agriculture School of Agricultural Sciences São Paulo State University (UNESP)

The effect of elevated [CO

Although Selenium (Se) stress is relatively well known for causing growth inhibition, its effects on primary metabolism remain rather unclear. Here, we characterized both the modulation of the expression of specific genes and the metabolic adjustments in Arabidopsis thaliana in response to changes in Se level in the soil. Se treatment culminated with strong inhibition of both shoot and root growth. Notably, growth inhibition in Se-treated plants was associated with an incomplete mobilization of starch during the night. Minor changes in amino acids levels were observed in shoots and roots of plants treated with Se whereas the pool size of tricarboxylic acid (TCA) cycle intermediates in root was not altered in response to Se. By contrast, decreased levels of organic acids involved in the first part of the TCA cycle were observed in shoots of Se-treated plants. Furthermore, decreased expression levels of expansins and endotransglucosylases/endohydrolases (XHTs) genes were observed after Se treatment, coupled with a significant decrease in the levels of essential elements. Collectively, our results revealed an exquisite interaction between energy metabolism and Se-mediated control of growth in Arabidopsis thaliana to coordinate cell wall extension, starch turnover and the levels of a few essential nutrients.

Obtaining a high yield of good quality fruits is one of the main challenges of the tomato crop. The enhancement in plant density promotes a reduction in the fruit fresh mass and an increase the yield per area. On the other hand, commercialization parameters take into account number and fresh mass of fruits. This study aimed at evaluating the yield and fruit quality of indeterminate growth hybrid tomato (Rebeca), cultivated in a hydroponic system, with different planting densities and number of bunches per plant. The experiment was conducted under greenhouse conditions, in a sub-irrigation system containing expanded clay as substrate. A split-plot randomized block design, with three replications, was used. In the plots, four planting densities (11.1 plants m-2, 8.3 plants m-2, 6.6 plants m-2 and 5.5 plants m-2) were allocated and, in the subplots, the number of bunches per plant (one or two). The total yield was influenced by the interaction planting density x number of bunches per plant. The treatment that allowed the highest yield was 11.1 plants m-2 with two bunches, with 22.61 kg m-2 or 226.1 t ha-1, in a crop cycle of 134 days. The observed variations for the nutrient contents of leaves and fruits of tomato plants with one or two bunches, at densities of 5.5-11.1 plants m-2, do not compromise the fruit quality nor influence the production of tradable fruits, using the hydroponic system. RESUMO A obtenção de frutos de boa qualidade e com alta produtividade é um dos principais desafios da cultura do tomateiro. Com o adensamento de cultivo, há redução na massa fresca de frutos e aumento na produtividade por área; porém, a comercialização considera o número e a massa fresca de frutos. Objetivou-se avaliar a produtividade e a qualidade de frutos de tomateiro híbrido de crescimento indeterminado (Rebeca), cultivado em sistema hidropônico, com diferentes densidades de plantio e número de cachos por planta. O experimento foi conduzido em casa-de-vegetação, em sistema de subirrigação contendo argila expandida como substrato. O delineamento foi em blocos ao acaso, com parcelas subdivididas e três repetições. Nas parcelas, foram alocadas quatro densidades de plantio (11,1 plantas m-2; 8,3 plantas m-2; 6,6 plantas m-2; e 5,5 plantas m-2) e, nas subparcelas, o número de cachos por planta (um ou dois). A produtividade total foi influenciada pela interação densidade de plantio x número de cachos por planta. O tratamento que possibilitou maior produção foi o de 11,1 plantas m-2 com dois cachos, com 22,61 kg m-2 ou 226,1 t ha-1, em um ciclo de cultivo de 134 dias. As variações observadas para os teores de nutrientes minerais nas folhas e frutos do tomateiro com um ou dois cachos, em densidades de 5,5-11,1 plantas m-2, não comprometem a qualidade dos frutos e nem influenciam na produção de frutos comercializáveis, no cultivo hidropônico.

Aluminum-induced citric acid (CA) root secretion is a widely accepted mechanism to explain Al-resistance in maize. Nonetheless, several aspects of this mechanism remain controversial. In this study, we used paclobutrazol (PBZ), a plant growth retardant, to gain new insights into the relationship between Δ5-sterol composition, membrane permeability, (PM) H+-ATPase activity and CA secretion in an Al-sensitive (UFVM-100) and Al-resistant (UFVM-200) maize genotypes challenged with Al. The Al-sensitive genotype displayed greater concentrations of Al in the root tips and greater inhibition of root elongation (RE), which was accompanied by greater electrolyte leakage and greater reduction in the Δ5-sterols content after Al treatment. CA secretion by roots increased in both genotypes after Al treatment but to a greater extent in the Al-resistant genotype. The (PM) H+-ATPase activity was down-regulated in the sensitive cultivar and up-regulated in its resistant counterpart upon Al treatment. A significant correlation between (PM) H+-ATPase activity and CA secretion was observed, but only in the Al-resistant genotype. Upon adding PBZ to the Al-treated plants, differences in the RE and Δ5-sterol composition between the maize genotypes were fully abolished, whereas genotypic differences in CA secretion and (PM) H+-ATPase activity were reduced but not completely eliminated. Taken together, this information suggests the existence of other processes or mechanisms operating in the Al resistance in these two maize genotypes.

Secretion of organic acids (OAs) by roots has been suggested to be an important mechanism of Al resistance in many species. In Stylosanthes, the participation of OAs in the mechanism of Al resistance is poorly understood. We aimed to study the production and secretion of OAs by two Brazilian Stylosanthes species with different Al resistance. Stylosanthes capitata and S. guianensis were treated with Al at different concentrations in 0.5 mM CaCl2 (pH 4.0), and then root elongation, Al and OA content, OA secretion into the external solution, and the activity of citrate synthase (CS) were measured. Al-induced secretion of citric acid was also evaluated in the presence of protein synthesis and anion channel inhibitors. S. guianensis accumulated lower amounts of Al in its roots and displayed less inhibition of root elongation compared to S. capitata. Citric and malic acids were the most abundant OAs in the roots, and their content decreased with the Al treatment, except for citric acid in S. guianensis. Citric acid was the only OA secreted into the nutrient solution by the Al-treated plants of both species, but more by S. guianensis. Citrase synthase activity decreased in S. capitata but increased in S. guianensis with the Al treatment, and it may have a crucial role in the maintenance of citric acid content in the roots of S. guianensis. The use of anion channel and protein synthesis inhibitors reveal that anion channels were likely involved in the secretion of citric acid, and channel protein transcription was up-regulated by exposure to Al in Stylosanthes.

Although Selenium (Se) stress is relatively well known for causing growth inhibition, its effects on primary metabolism remain rather unclear. Here, we characterized both the modulation of the expression of specific genes and the metabolic adjustments in Arabidopsis thaliana in response to changes in Se level in the soil. Se treatment culminated with strong inhibition of both shoot and root growth. Notably, growth inhibition in Se-treated plants was associated with an incomplete mobilization of starch during the night. Minor changes in amino acids levels were observed in shoots and roots of plants treated with Se whereas the pool size of tricarboxylic acid (TCA) cycle intermediates in root was not altered in response to Se. By contrast, decreased levels of organic acids involved in the first part of the TCA cycle were observed in shoots of Se-treated plants. Furthermore, decreased expression levels of expansins and endotransglucosylases/endohydrolases (XHTs) genes were observed after Se treatment, coupled with a significant decrease in the levels of essential elements. Collectively, our results revealed an exquisite interaction between energy metabolism and Se-mediated control of growth in Arabidopsis thaliana to coordinate cell wall extension, starch turnover and the levels of a few essential nutrients.

As auxinas AIA (acido indol-3-acetico), 2,4-D (acido 2,4-diclorofenoxiacetico) e 2,4,5-T (acido 2,4,5-triclorofenoxiacetico) foram aplicadas em plantas de milho ( Zea mays , monocotiledonea) e feijao ( Phaseolus vulgaris , dicotiledonea), visando compreender os mecanismos que levam a respostas diferenciais das plantas de milho e feijao em relacao ao metabolismo do etileno. Plantas de milho tratadas com as auxinas nao produziram etileno, ja o feijao produziu bastante apos o tratamento. Apos pulverizacao com as auxinas, o milho nao exibiu producao do acido 1-carboxilico-1-amino-ciclopropano (ACC), fato observado no feijoeiro O rendimento quântico maximo do fotossistema II (razao F v / F m ) e os niveis dos pigmentos fotossinteticos nao foram alterados em plantas de milho tratadas com as auxinas. As plantas de feijao mostraram quedas significativas em ambas variaveis apos o tratamento com 2,4-D e 2,4,5-T, mas nao com o AIA. A reducao nos niveis das clorofilas em plantas de feijao tratadas com 2,4-D e 2,4,5-T relacionou-se com a clorose observada, uma vez que ocorreu uma degradacao mais acentuada das clorofilas do que dos carotenoides. As xantofilas tambem tiveram uma degradacao mais acentuada do que o alfa e beta caroteno em plantas de feijao tratadas com 2,4-D e 2,4,5-T. Quando aminoetoxivinilglicina (AVG) e Co 2+ foram fornecidos as plantas de feijao, conjuntamente com as auxinas, nao ocorreu queda na razao F v / F m e nem no nivel dos pigmentos, com excecao do alfa caroteno.