Soil salinity directly affects plants, interfering in the emission of fluorescence, and promoting the degradation of photosynthetic pigments. Thus, estimating the damage to the photosynthetic apparatus caused by saline water is an important tool to detect abiotic stresses. For this purpose, sorghum plants were cultivated in a greenhouse and irrigated with two water sources (NaCl and salt mixture) with six levels of electrical conductivity (EC) (0, 2.5, 5, 7.5, 10, and 12.5 dS m-1), forming a 6 × 2 factorial in randomized blocks with four repetitions. At 60 days after sowing, the photosynthetic pigments were quantified, the chlorophyll a fluorescence parameters (initial fluorescence [F0]; variable fluorescence [Fv]; maximum fluorescence [Fm]; quantum efficiency of photosystem II - PSII [Fv/Fm]; electron flux per reaction center [ET0/CR]; quantum energy dissipation [DI0/CR] and quantum yield for heat dissipation [φD0]) were evaluated. The photosynthetic pigments were decreased with an increase in the salinity of the irrigation water, and were more expressive at higher electrical conductivities. With the wear on the photosynthetic apparatus by the increase in salinity, a reduction in the emission of the chlorophyll a fluorescence was observed, pointing to a possible photoinhibition of photosystem II.
Sorghum bicolor (L.) Moench, one of the most important dryland cereal crops, is moderately tolerant of soil salinity, a rapidly increasing agricultural problem due to inappropriate irrigation management and salt water intrusion into crop lands as a result of climate change. The mechanisms for sorghum’s tolerance of high soil salinity have not been elucidated. This study tested whether sorghum plants adapt to salinity stress via stomatal regulation or osmotic adjustment. Sorghum plants were treated with one of seven concentrations of NaCl (0, 20, 40, 60, 80, or 100 mM). Leaf gas exchange (net CO2 assimilation (A), transpiration (Tr); stomatal conductance of water vapor (gs), intrinsic water use efficiency (WUE)), and water (Ψw), osmotic (Ψo), and turgor Ψt potentials were evaluated at 40 days after the imposition of salinity treatments. Plants exhibited decreased A, gs, and Tr with increasing salinity, whereas WUE was not affected by NaCl treatment. Additionally, plants exhibited osmotic adjustment to increasing salinity. Thus, sorghum appears to adapt to high soil salinity via both osmotic adjustment and stomatal regulation.
Crambe is a promising crop for biodiesel production. However, there is no much information available about techniques and research regarding the best performance in different regions to explore its potential. The objective of this study was to evaluate the effect of cadmium, chromium, copper and zinc in the development of crambe. The study was carried out in a greenhouse and it consisted of four independent experiments in completely randomized design, with three replications. Four metals with five levels were applied: 0, 10, 15, 20 and 25 mg•kg −1 for copper, cadmium, chromium; and 0, 20, 30, 40 and 50 mg•kg −1 for zinc, in order to evaluate the growth of crambe. Data were subjected to analysis of variance and comparison of means by Tukey test at 1 and 5% significance. Despite doses of cadmium, chromium, copper and zinc in growing crambe have influenced in some of the evaluated variables of the plants, in general, their development was similar in relation to doses and the metals applied. The importance of cultivating crambe is related to grain production, based on this, copper and cadmium decreased this production.
R E S U M OA mamoneira é bastante sensível à competição, havendo necessidade de ampliar as alternativas de manejo de plantas daninhas, considerando-se principalmente as opções de herbicidas seletivos, visando favorecer a expansão das áreas de cultivo. O objetivo deste trabalho foi avaliar a seletividade do herbicida halosulfuron-methyl para a cultura da mamoneira aplicado em pré-emergência, antes da semeadura. Dois experimentos foram conduzidos em condições de casa-de-vegetação, um com solo arenoso e outro com francoargilo-arenoso, em delineamento inteiramente casualizado com quatro repetições. Os tratamentos se constituíram de cinco períodos entre a aplicação do herbicida e a semeadura (0, 7, 14, 21 e 28 dias) e uma testemunha sem aplicação. As avaliações realizadas foram: altura de plantas aos 7, 14, 21 e 28 dias após a emergência (DAE); diâmetro do caule, área foliar, volume de raízes, massa seca de parte aérea e raízes aos 28 DAE. Halosulfuron-methyl (112,5 g ha -1) é seletivo para a cultura da mamoneira quando aplicado na modalidade de pré-emergência, antes da semeadura. Selectivity of halosulfuron-methyl applied in preemergence of castor bean crop A B S T R A C TCastor bean is very sensitive to competition, being necessary to expand the alternatives for weed management, principally considering the selective herbicide options, aiming to contribute to the expansion of the cultivated areas. The aim of this study was to evaluate the selectivity of the herbicide halosulfuron-methyl applied to castor bean crop in preemergence, before seeding. Two trials were conducted under greenhouse conditions, one with sandy and other with sandy clay loam soil, in a completely randomized design with four replications. The treatments corresponded to five periods between herbicide application and seeding (0, 7, 14, 21 and 28 days) and a control without application. The evaluations made were: plant height at 7, 14, 21 and 28 days after emergence (DAE); stem diameter, leaf area, root volume, dry mass of aerial part and roots at 28 DAE. ) is selective to castor bean crop, when applied at preemergence modality, before seeding. Palavras-chave:herbicida tolerância Ricinus communis L. plantio direto
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