Role of antioxidant enzyme responses and phytochelatins in tolerance strategies of Alhagi camelorum Fisch growing on copper mine

This study was performed to clarify some aspects of tolerance mechanisms against excess copper (Cu) in Alhagi camelorum Fisch, a dominant wild type plant growing in a Cu-contaminated zone and its vicinity. Total and available copper was at toxic levels for plants growing on the contaminated soil. There were no visual and onspicuous symptoms of Cu toxicity in this plant species. Most of the excess Cu in soil was transferred to and accumulated in plant leaves in which the storage rate in vacuoles and chloroplasts was 48% and 7% respectively. There was an insignificant decrease in chlorophyll content and a significant increase in tissues phytochelatins and antioxidant enzyme activities in plants collected from the contaminated zone as compared to plants of the same species growing on uncontaminated soil. We also observed significant elevation in oxidative damage biomarkers, malondialdehyde and dityrosine, when the aerial parts of Alhagi camelorum were compared with the same parts of the plant collected from an uncontaminated zone. Alhagi camelorum elevated its antioxidative enzyme activities, phytochelatins and accumulated the excess of Cu in leaf vacuoles in response to Cu-toxicity as tolerance strategy

RESPOSTA DE SEIS GENÓTIPOS DE CANOLA A ESTRESSE HÍDRICO E APLICAÇÃO DE HIDROGEL

The hydrogel amendments may improve seedling growth and establishment by increasing water retention capacity of soils and regulation of plants available water supplies, especially under arid environments. This study was conducted to evaluate the role of super absorbent polymer use in oilseed rape (Brassica napus L.) genotypes, under drought stress, evaluating some agronomic (total biomass, seed yield, yield components and harvest index) and physiological characters (chlorophyll content). The experiment was carried out in the research farm of the Seed and Plant Improvement Institute, in 2007-2008, in Karaj, Iran (35°59´N, 50°75E, 151 m altitude), as a randomized complete block design, with factorial split-plot arrangement, with three replications. The irrigation strategy had two levels (irrigation after 80% of water evaporation, from class A Pan as control, and drought stress, starting from the flowering stage to physiological maturity) and the application of super absorbent also occurred at two levels (absence of super absorbent as control, and application of super absorbent at 7% concentration), as main plots. Genotypes Rgs003 (V1), Sarigol (V2), Option500 (V3), Hyola401 (V4), Hyola330 (V5), and Hyola420 (V6) were allotted to subplots. Results showed a significant difference between irrigation treatments, presence of super absorbent, and genotypes on agronomic and physiological characters. Water stress decreased total biomass, seed yield components, harvest index, and chlorophyll content. On the other hand, under field conditions, the use of 7% of super absorbent increased agronomic and physiological characters performance. Field results showed that drought stress and absence of super absorbent lead to a decrease in all agronomic parameters. These results may be due to the reduction of photosynthesis and chlorophyll content. In our study, the super absorbent was able to reduce the destructive effect of water deficiency, by absorbing and preserving water and improving several agronomic characters. Observing the increased yield and its components and decreasing plant water requirement, it seems that this material is technically acceptable. KEY-WORDS: Brassica napus; hydrogel; water stress; agronomic character; chlorophyll content.Os hidrogéis condicionadores podem melhorar o estabelecimento e crescimento de plântulas, pelo aumento da capacidade de retenção de água dos solos e regulagem do suprimento de água disponível para as plantas, especialmente em ambientes áridos. Este estudo foi desenvolvido para avaliar o papel de polímero superabsorvente, em genótipos de canola (Brassica napus L.), sob estresse hídrico, avaliando-se alguns caracteres agronômicos (biomassa total, produção de grãos, componentes da produção e índice de colheita) e fisiológicos (conteúdo de clorofila). O experimento foi conduzido na estação experimental do Instituto para Melhoramento de Sementes e Plantas, em 2007-2008, em Karaj, Irã (35°59´N, 50°75’E, 151 m de altitude), em desenho blocos ao acaso e arranjo fatorial de parcelas divididas, com três repetições. A irrigação teve dois níveis (irrigação após evaporação de 80% de tanque classe A, como testemunha, e estresse hídrico, da floração à maturidade fisiológica) e aplicação de superabsorvente, em dois níveis (ausência de superabsorvente, como testemunha, e aplicação, na concentração de 7%). Os genótipos Rgs003 (V1), Sarigol (V2), Option500 (V3), Hyola 401 (V4), Hyola330 (V5) e Hyola420 (V6) foram alocados em subparcelas. Os resultados mostraram diferença significativa entre os tratamentos de irrigação, superabsorvente e genótipos, nos caracteres agronômicos e fisiológicos. A deficiência de água reduziu a biomassa total, os componentes da produção de grãos, o índice de colheita e o conteúdo de clorofila. Por outro lado, sob condições de campo, o uso de superabsorvente, a 7%, aumentou o desempenho dos caracteres agronômicos e fisiológicos. Os resultados de campo mostraram que a deficiência de água e a ausência de superabsorvente levaram a um decréscimo em todos os parâmetros agronômicos. Estes resultados podem ser creditados à redução da fotossíntese e do conteúdo de clorofila. Neste estudo, o superabsorvente foi capaz de reduzir o efeito destruidor da deficiência de água, pela absorção e preservação da água, o que redundou em melhoria, em diversos caracteres agronômicos. Observando-se o aumento da produção e de seus componentes e da redução da demanda de água, conclui-se que o material é tecnicamente aceitável. PALAVRAS-CHAVE: Brassica napus; hidrogel; estresse hídrico; caracteres agronômicos; conteúdo de clorofila

Response of antioxidant compounds to selenium and salicylic acid in wheat cultivars under dry land conditions

In the present study, three dry land wheat cultivars, Azar 2, Sardary and Rasad, were tested for antioxidant enzyme activity, proline, malondialdehyde (MDA) and dityrosine (DT) content and grain yield after treatment with selenium and salicylic acid (SA). A factorial field experiment was carried out based on a completely randomized block design with three replicates. The experimental factors were three levels of salicylic acid (without SA; seed priming with 0.5 mM SA; seed priming + spraying with 1 mM SA) and two levels of selenium (0 and 20 g/ha). Significant increases in the activity of the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) enzymes and in the proline level were observed after treatment in the leaves of the three genotypes investigated, but this was associated with reduced MDA and DT content. The application of SA as seed priming and the foliar application of Se also increased the grain yield. These results suggest that cultivars exhibiting high antioxidant enzyme activity and proline content under dry land conditions may provide better drought tolerance in wheat.</jats:p