A B S T R A C TLeaf gas exchanges in plants and soil respiration are important tools for assessing the effects of salinity on the soil-plant system. An experiment was conducted with cowpea irrigated with saline water (0, 2.5, 5.0, 7.5, 10.0 and 12.5 dS m -1 ) prepared with two sources: NaCl and a mixture of Ca, Mg, Na, K and Cl ions in a randomized block design and a 6 x 2 factorial scheme, with four replicates, totaling 48 experimental plots. At 20 days after planting (DAP), plants were evaluated for net photosynthesis (A), stomatal conductance (gs) and transpiration (E) using the Infra-Red Gas Analyzer (Model XT6400-LICOR), and water use efficiency, intrinsic water use efficiency and instantaneous efficiency of carboxylation were calculated. At 60 DAP, the soil CO 2 efflux (soil respiration) was determined with a camera (Model 6400-09-LICOR). Salinity caused reductions in A, gs and E. However, the salt source did not have significant effect on these variables. Soil CO 2 efflux was reduced with the increase in the electrical conductivity, especially in the mixture of ions.Trocas gasosas em feijão-caupi e efluxo de CO 2 do solo irrigado com água salina R E S U M O As trocas gasosas em plantas e a respiração do solo são ferramentas importantes para avaliar os efeitos da salinidade no sistema solo-planta. Com este propósito conduziu-se um experimento com feijão-caupi irrigado com seis níveis de condutividade elétrica (0; 2,5; 5,0; 7,5; 10,0 e 12,5 dS m -1 ) elaborados com duas fontes: NaCl e uma mistura de íons de Ca, Mg, Na, K e Cl, em blocos ao acaso e arranjo fatorial 6 x 2, com 4 repetições totalizando 48 parcelas; aos 20 dias após o plantio (DAP) foram determinadas fotossíntese líquida (A), condutância estomática (gs) e transpiração (E) com o Infra-Red Gas Analyzer (Modelo XT6400-Licor) e se calcularam a eficiência do uso da água, a eficiência intrínseca do uso da água e a eficiência instantânea de carboxilação; aos 60 DAP determinou-se o efluxo de CO 2 (respiração do solo) com uma câmara de solo (Modelo 6400-09-LICOR). Observaram-se reduções de A, gs e E com o aumento da salinidade; entretanto, a fonte de sal não apresentou efeito significativo para tais variáveis; já para a respiração do solo ocorreu redução com o aumento da condutividade elétrica da água de irrigação sendo mais pronunciado quando se utilizou somente a mistura de sais.
Given that cadmium (Cd) poses high persistence in the environment and toxicity to humans, strategies to either decrease or avoid Cd entry in the trophic chain are fundamental to secure food safety. Here we assessed the effects of applying rates of Si as a diatomaceous Earth-based fertilizer on the amelioration of Cd toxicity towards maize plants grown on soil with or without pH correction. Besides determining Si and Cd concentrations, we also evaluated plant accumulation of nutrients (N, P, K, Ca, Mg, Fe, Mn, Cu, and Zn) as a function of Si doses applied to the soil. Results showed that both the Si application and the liming had a positive effect on biomass and nutrient uptake, but the Si effect on plants’ performance took place irrespectively to the soil pH. Silicon ameliorated Cd phytotoxicity in both limed and unlimed soils by decreasing Cd concentration in shoots and improving biomass yield and plant nutrition. Silicon alleviation of Cd-inhibitory effects on plants was more effective in the unlimed soil owing to the higher Cd availability in acidic soils. Also, taking into account the reduced transfer of Cd to shoots driven by Si, lower Cd accumulation in maize grains is likely, with implications to food safety. So, further studies on field conditions are warranted.
Purpose: Silicon (Si) acts to reduce biotic and abiotic stresses in plants. Herein, we aimed to assess the impact of an amorphous silica-based fertilizer (ASF) applied to soil on the yield, mineral nutrition, chlorophyll uorescence, and postharvest quality of two cultivars of table grapes grown in a semiarid climate.Methods: The cultivars Arra 15 and BRS Vitoria were submitted to the treatments control, 175 or 350 kg ha -1 ASF.Leaf and fruit samples were collected and analyzed for Si, nutrients, and postharvest quality characteristics. Photosynthetic e ciency was assessed by measuring chlorophyll a uorescence .Results: Both cultivars showed signi cant responses to Si with the ASF rates of 175 and 350 kg ha -1 . The characteristics improved through ASF application compared to the control were: fruit production (6 -22 %), bunch weight (11 %), number of berries (20 -34 %), berry crunchiness (20 %), the content of total soluble solids (13 -20 %), the titratable acidity (13 %), the accumulation of macro and micronutrients (12 -45 %) and the photosynthetic e ciency (5 -33 %).Conclusions: Soil-applied Si increases the yield and quality of grapes by improving the plant response to abiotic stresses, being such effects more signi cant in the dry season.
Purpose: Silicon (Si) acts to reduce biotic and abiotic stresses in plants. Herein, we aimed to assess the impact of an amorphous silica-based fertilizer (ASF) applied to soil on the yield, mineral nutrition, chlorophyll fluorescence, and postharvest quality of two cultivars of table grapes grown in a semiarid climate. Methods: The cultivars Arra 15 and BRS Vitoria were submitted to the treatments control, 175 or 350 kg ha-1 ASF. Leaf and fruit samples were collected and analyzed for Si, nutrients, and postharvest quality characteristics. Photosynthetic efficiency was assessed by measuring chlorophyll a fluorescence . Results: Both cultivars showed significant responses to Si with the ASF rates of 175 and 350 kg ha-1. The characteristics improved through ASF application compared to the control were: fruit production (6 - 22 %), bunch weight (11 %), number of berries (20 - 34 %), berry crunchiness (20 %), the content of total soluble solids (13 – 20 %), the titratable acidity (13 %), the accumulation of macro and micronutrients (12 – 45 %) and the photosynthetic efficiency (5 – 33 %). Conclusions: Soil-applied Si increases the yield and quality of grapes by improving the plant response to abiotic stresses, being such effects more significant in the dry season.
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