Susceptibility to weathering damage and oxidative stress on soybean seeds with different lignin contents in the seed coat.

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Metodologia para transformação de soja via Agrobacterium tumefaciens.

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Expression profile of rice Hsp genes under anoxic stress.

ABSTRACT: Although flooding is one of the most important environmental stresses worldwide, not all plant species are intolerant to its effects. Species from semi-aquatic environments, such as rice, have the capacity to cope with flooding stress. Heat-shock proteins (Hsps) are thought to contribute to cellular homeostasis under both optimal and adverse growth conditions. Studies of gene expression in plants exposed to low levels of oxygen revealed the up-regulation of Hsp genes. However, it is not clear whether Hsp genes are transcribed as a function of tolerance or whether they represent a response to anoxic stress. Therefore, the accumulation of Hsp gene transcripts was investigated in two different cultivars, 'Nipponbare' (flooding tolerant) and 'IPSL 2070' (flooding sensitive), subjected to anoxic stress. Fifteen-day-old rice root seedlings from both cultivars were used. Four different treatments were performed: no anoxia (control); 24-h anoxia; 48-h; and 72 anoxia; and 72-h anoxia. Anoxic stress was confirmed by the increased gene expression of alcohol dehydrogenase. The data obtained showed that both rice cultivars ('Nipponbare' and 'IPSL 2070') accumulated Hsp gene transcripts under anoxic stress; however, the majority of the Hsp genes evaluated were responsive to anoxic stress in 'IPSL 2070' (flooding sensitive), whereas in 'Nipponbare' (flooding tolerant), only six genes were highly up-regulated. This suggests that although Hsps have an important role in the response to anoxia, they are not the major cause of tolerance

Parâmetros fisiológicos e de crescimento em cultivares de girassol submetidas ao estresse hídrico em condições controladas.

RESUMO; O objetivo deste trabalho foi avaliar a reação de seis cultivares de girassol (BRS 323, BRS 321, M 734, BR G 43, AGUARÁ 04 e AGUARÁ 06), submetidas ao estresse por déficit hídrico em casa de vegetação. Os tratamentos foram dispostos em cinco blocos casualizados. O estresse por déficit hídrico foi aplicado quando as plantas apresentaram a sexta folha completamente expandida, sendo cada cultivar submetida a duas condições hídricas: i) déficit hídrico, com supressão total da irrigação e ii) manutenção da capacidade de campo, com irrigação diária e suficiente para saturar o substrato contido nos vasos. Foram avaliados os parâmetros de crescimento MSPA (matéria seca da parte aérea), MSR (matéria seca das raízes) e relação MSR/MSPA. Além disso, foram determinadas a fotossíntese líquida (A), a condutância estomática ao vapor de água (gs) e o conteúdo de clorofila pelo índice SPAD. Os resultados foram submetidos à analise de variância (ANOVA), teste F e comparadas pelo teste de Snott-Knott a 5% de probabilidade. Foi observado o efeito negativo do estresse por déficit hídrico para todas as variáveis de crescimento analisadas. A fotossíntese e condutância estomática também foram afetadas em função do estresse. As cultivares BRG 43 e AGUARÁ 04 foram as que apresentaram maior sensibilidade ao estresse, enquanto AGUARÁ 06, BRS 321 e M 734 mostraram melhor adaptação. ABSTRACT: The aim of this study was to evaluate six sunflower cultivars (BRS 323, BRS 321, M 734, G BR 43, AGUARA 04 and AGUARA 06), submitted to drought stress under greenhouse conditions. The treatments were arranged in five randomized blocks. The drought stress was applied when plants showed sixth fully expanded leaf. Each cultivar was submitted under two water conditions: i) water deficit, with total suppression of irrigation and ii) maintenance of field capacity, with daily irrigation sufficient to saturate the substrate. The growth parameters SDW (shoot dry weight), RDW (root dry weight) and RDW/SDW ratio were evaluated. Moreover it was determined photosynthesis (A), stomatal conductance (Gs) and the chlorophyll content by SPAD index. The results were submitted to analysis of variance (ANOVA) and the means compared by Snott-Knott test at 5% of probability. According to results negative effect of drought was detected for all plant growth parameters. The photosynthesis and stomatal conductance were also negatively affected by drought stress. Cultivars BRG 43 and AGUARÁ 04 were more sensitivity to stress, while the cultivars AGUARÁ 06, BRS 321 and M 734 showed better adaptation in stress conditions