Water stress limits the initial growth and development of maize mass and grain, as well as the physiological process for absorbing the amount of mineral elements. The objective was to evaluate the effect of silicon on germination and growth of corn seedlings submitted to water deficit. The experiment was carried out in the laboratory and the experimental design was completely randomized (factorial 3 × 4), with three concentrations of calcium silicate (0.0; 1.0 and 2.0 mM) and 4 solutions of PEG-6000 to simulate different osmotic potentials (0, 0; -0.3; -0.6; -0.9 MPa). Germination percentage, germination speed index (GSI), mean germination time (MGT), percentage of non-germinated and abnormal germinated, length and dry matter of shoot, root and total seedlings were evaluated. Water deficiency reduced the parameters TG, GSI and MGT. The water deficit reduce the MSPA, MSR and MST with more than 80% reduction in mass from seedlings without deficiency to seedlings with deficiency. For CPA, CR and CT there was a reduction of at least 87%, 70% and 77%, respectively, among seeds without deficiency compared to seeds submitted to deficiency. The use of silicon in corn seeds did not attenuate the stress caused by water deficit simulated by PEG-6000.
The aim of this study is to assess the effect of sodium nitroprusside-NPS (nitric oxide donor) on the emergence and initial growth of maize seedlings (Zea mays L.) subjected to different copper concentrations. The study followed a completely randomized design at 4 x 3 factorial arrangement, with 12 treatments and 8 repetitions, totally 96 trays with 25 seedlings per repetition. Seedlings were soaked in sodium nitroprusside (SNP) solution (0.75 and 150 µM - donor), sodium ferrocyanide (SF) (0.75 and 150 µM - compensator) and deionized water (control) on Germitest paper for 48 hours. Next, they were placed on sand saturated with CuSO4.5H2O at concentrations of 0, 100 and 200 µM. The results showed that SNP doses were not capable of mitigating copper toxicity in seedling emergence, influencing emergence speed coefficient and prolonging the mean emergence time of plants subjected to copper concentrations of 100 µM and 200 µM. Copper concentrations rose the number of abnormal seedlings and had negative influence on plant biometrics and biomass. Copper concentration of 200 µM increased proline content in the roots. NPS and sodium ferrocyanide application had effect on emergence speed index, shoot and root dry mass and on proline content in the shoot and roots. This outcome highlights that such effects were caused by treatments related to release of cyanide found in sodium nitroprusside (SNP), rather than to nitric oxide (NO)
Objetivou-se com o estudo avaliar a ação da Azospirillum brasilense e ácido jasmônico como atenuadores na produtividade nas espigas de milho crioulo em diferentes lâminas de água. O experimento foi conduzido em casa de vegetação, pertencente a Universidade Federal Rural da Amazônia (UFRA) cidade de Belém (PA), o delineamento experimental foi inteiramente casualizado em esquema fatorial do tipo 2 A. brasilense (ausência e presença) x 3 Ácido Jasmônico (0,10 e 20 µmol.L-1) x 3 lâminas de irrigação (60, 80 e 100% da CC – Capacidade de Campo), contendo 4 repetições, totalizando 72 unidades experimentais, utilizando sementes de milho crioulo. Foram realizadas avaliações no estádio R6-maturidade fisiológica: altura de inserção da espiga, diâmetro da espiga com palha, diâmetro da espiga sem palha, diâmetro do sabugo, massa da espiga com palha, massa da espiga sem palha, massa do sabugo, comprimento da espiga, número de fileiras por espiga, número de grãos por espiga, massa de grãos por espiga. Os dados experimentais foram submetidos aos testes de Shapiro-Wilks e Levene à 5% de significância. Posteriormente, realizou-se análise de variância, na qual procedeu-se aos desdobramentos que se mostraram significativos. Os efeitos das doses de ácido jasmônico na presença e ausência da A. brasilense e nas condições de deficiência hídrica foram estudados mediante análise de regressão polinomial, observando-se os resultados do teste F (p<0,05) da análise de variância, por meio do software estatístico SISVAR. A variável de MGE apresentou ajuste ao modelo quadrático nos estados de 80% e 100% da CC na ausência e presença da A. brasilense com melhor Valor matemático de eficiência técnica (Ymet) em 100% da CC na presença de A. brasilense, 41,48% superior ao tratamento de 80% da CC. Na variável NGE as condições de 60%, 80% e 100% da CC na ausência de A. brasilense apresentaram ajuste ao modelo quadrático obtendo melhor Ymet em 100% da CC, quantidade 50,55% maior em relação a 80% da CC e 66,35% em comparação com 60% da CC. A lâmina de 80% da CC apresentou melhores interações entre a A. brasilense e o ácido Jasmônico nas variáveis estudadas. O ácido jasmônico obteve melhores respostas isoladamente entre as lâminas de irrigação. Os resultados para a lâmina de 60% da CC com uso de atenuantes foram inferiores aos das demais lâminas. O tratamento de 10 µmol L-1 de AJ foi o que mais se aproximou das dosagens estimadas como positivas para a produtividade das espigas.
Cowpea (Vigna unguiculata (L.) Walp.) is a legume widely cultivated by small, medium and large producers in several Brazilian regions. However, one of the concerns for the production of cowpea in Brazil in recent years is the low rainfall activity in these regions, which generates the accumulation of salts on the surface. The objective of this work was to evaluate the effects of salt stress on growth parameters and enzyme activity in cowpea plants at different concentrations of brassinosteroids. Experiment was developed in a greenhouse using a completely randomized experimental design in a 3 x 3 factorial scheme. The treatments consisted of three levels of brassinosteroids (0, 3 and 6 µM EBL) and three levels of salt stress (0, 50 and 100 mM NaCl). Growth factors (height, diameter and number of leaves) decreased in the saline condition. With the presence of brassinosteroid the height did not increase, but the number of leaves did, mainly in the saline dosage of 100 mM NaCl. In the variable membrane integrity, brassinosteroid was efficient in both salinity dosages, the same not happening with the relative water content, where the saline condition did not affect the amount of water in the vegetable, with the application of brassino it remained high, decreasing only at dosage 100 mM NaCl. The nitrate reductase enzyme was greatly affected in the root system even with the application of increasing doses of brassino. Therefore, brassinosteroids as a promoter of saline tolerance in cowpea seedlings was positive. The concentration of 3µM of EBL provided the most satisfactory effect in tolerating the deleterious effects of the saline condition. The same cannot be concluded for the concentration of 6µM of EBL that did not promote tolerance to some variables.
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