Supply of sulphur to S-deficient young barley seedlings restores their capability to cope with iron shortage

The effect of the S nutritional status on a plant's capability to cope with Fe shortage was studied in solution cultivation experiments in barley (Hordeum vulgare L. cv. Europa). Barley is a Strategy II plant and responds to Fe deficiency by secretion of chelating compounds, phytosiderophores (PS). All PS are derived from nicotianamine whose precursor is methionine. This suggests that a long-term supply of an inadequate amount of S could reduce a plant's capability to respond to Fe deficiency by limiting the rate of PS biosynthesis. The responses of barley (Hordeum vulgare L. cv. Europa) plants grown for 12 d on Fe-free nutrient solutions (NS) containing 0 or 1.2 mM SO42-, was examined after 24 h or 48 h from transfer to NS containing 1.2 mM SO42-. After the supply of S was restored to S-deprived plants, an increase in PS release in root exudates was evident after 24 h of growth in S-sufficient NS and the increment reached values up to 4-fold higher than the control 48 h after S resupply. When S was supplied to S-deficient plants, leaf ATPS (EC 2.7.7.4) and OASTL (EC 4.2.99.8) activities exhibited a progressive recovery. Furthermore, root HvST1 transcript abundance remained high for 48 h following S resupply and a significant increase in the level of root HvYS1 transcripts was also found after only 24 h of S resupply. Data support the idea that the extent to which the plant is able to cope with Fe starvation is strongly associated with its S nutritional status. In particular, our results are indicative that barley plants fully recover their capability to cope with Fe shortage after the supply of S is restored to S-deficient plants

Variação da temperatura de sementes de soja durante o armazenamento.

A temperatura é importante para a conservação de sementes armazenadas, pois é um dos principais fatores condicionantes das reações bioquímicas e do desenvolvimento de patógenos. Uma prática que vem sendo introduzida no processamento de sementes é o resfriamento artificial imediatamente após o beneficiamento, visando reduzir a perda da qualidade das sementes durante o armazenamento. Portanto, objetivou-se avaliar a temperatura de sementes de soja resfriadas artificialmente, durante o armazenamento. O experimento foi conduzido na empresa Sementes Campo Verde Ltda, no município de Campo Verde, Mato Grosso (latitude de 15° 32? 48?? S, longitude de 55° 10? 08?? W e altitude de 736 metros). Dois lotes de sementes de cada um dos três cultivares Monsoy 8757, TMG 115 RR e BRS Valiosa RR, um com sementes resfriadas e outro não foram utilizados. Cada lote era formado por 360 sacos de 40 kg, em 30 camadas de 12 sacos, e as sementes armazenadas em armazém com temperatura média anual de 24,7 ºC e 60,6% de umidade relativa doN ar. As sementes foram resfriadas pelo processo dinâmico, após o beneficiamento, com refrigerador CoolSeed, modelo PCS 80, com quatro circuitos refrigeradores, totalizando potência de 130 kW. O experimento foi instalado em abril de 2009 e cada lote tinha 12 unidades experimentais (sacos), em três porções do lote, basal, mediana e superior, de quatro sacos, distanciados por seis camadas de sacos entre si. A temperatura foi medida por saco, com uma termossonda digital, marca @GROS, a 30 cm e 60 cm de profundidade, na diagonal de cada saco, após: 0, 15, 30, 45, 60, 90, 120 e 150 dias. As temperaturas das massas de sementes de soja dos lotes resfriados ou não foram semelhantes com 15 dias do resfriamento e entraram em equilíbrio térmico com o ar do armazém

Response of barley plants to Fe deficiency and Cd contamination as affected by S starvation

Both Fe deficiency and Cd exposure induce rapid changes in the S nutritional requirement of plants. The aim of this work was to characterize the strategies adopted by plants to cope with both Fe deficiency (release of phytosiderophores) and Cd contamination [production of glutathione (GSH) and phytochelatins] when grown under conditions of limited S supply. Experiments were performed in hydroponics, using barley plants grown under S sufficiency (1.2mM sulphate) and S deficiency (0mM sulphate), with or without Fe III-EDTA at 0.08mM for 11d and subsequently exposed to 0.05mM Cd for 24h or 72h. In S-sufficient plants, Fe deficiency enhanced both root and shoot Cd concentrations and increased GSH and phytochelatin levels. In S-deficient plants, Fe starvation caused a slight increase in Cd concentration, but this change was accompanied neither by an increase in GSH nor by an accumulation of phytochelatins. Release of phytosiderophores, only detectable in Fe-deficient plants, was strongly decreased by S deficiency and further reduced after Cd treatment. In roots Cd exposure increased the expression of the high affinity sulphate transporter gene (HvST1) regardless of the S supply, and the expression of the Fe deficiency-responsive genes, HvYS1 and HvIDS2, irrespective of Fe supply. In conclusion, adequate S availability is necessary to cope with Fe deficiency and Cd toxicity in barley plants. Moreover, it appears that in Fe-deficient plants grown in the presence of Cd with limited S supply, sulphur may be preferentially employed in the pathway for biosynthesis of phytosiderophores, rather than for phytochelatin production

Desempenho de cultivares de mamona em sistema ecológico de produção de sementes.

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Implications of the clone by harvest interaction in the selection of sugarcane genotypes in a regionalized program

The recommendation of sugarcane clones depends on several factors, as the response or performance of the clones over different cuts or harvests. The clone by harvest interaction might be difficult to identify superior clones in the final stages of the sugarcane breeding program. Thus, the objective of this study was to investigate and describe the implications of the genotype by harvest interaction in the adaptability and stability of genotypes and delineation of mega-environments from a set of multi-environment trials. Fifteen clones and four checks were evaluated in eight environments. The trait TPH (tons of pol per hectare) was evaluated in two harvests (plant cane and ratoon cane) in 2010 and 2011. The joint analysis showed significance for harvest (H), environment (E), and genotype (G) effects. The interactions GxE, ExH, GxH, and ExGxH were also significant. The last three-way interaction indicated the differential response of the genotypes over environments, and that it depends on the harvests. The overall mean of the trials was 12.77 TPH. The coefficient of variation was 8.70% and the selective accuracy was 98.63%, indicating high experimental precision. The genotypes G4, G14, and G16 were statistically superior to the check varieties used; however, these genotypes did not show high stability as described by the additive main effects and multiplicative interaction method. There was a specific adaptation between the E7 and E5 environments and the G4 and G5 genotypes, respectively. In general, the grouping of the environments was inconsistent throughout the harvests, except for the E1 and E4 environments, which exhibited similarities for the different genotypes