Due to the weather changes prognostic for the coming years, the understanding of water deficit and physiological responses of plants to drought becomes an important requirement in order to develop technologies such as mechanisms to assist plants to cope with longer drought periods, which will be essential to maintenance of Brazilian and worldwide production. This study aimed to evaluate ecophysiological and anatomical aspects as well as the nitrate reductase activity in Siriema coffee seedlings subjected to four treatments: Daily irrigated, non-irrigated, re-irrigated 24 hours and re-irrigated 48 hours after different stress periods. Non-irrigation promoted a reduction in leaf water potential being accented from the ninth day of evaluation onwards. Re-irrigation promoted a partial recovery of the plant water potential. Non-irrigated plants showed an increase in stomatal resistance and reduction of transpiration and nitrate reductase activity. In the roots, there was a decrease in nitrate reductase activity under water stress. Leaf anatomical modifications were significant only for the adaxial surface epidermis and palisade parenchyma thickness, this latter characteristic being higher in control plants. Stomatal density and polar and equatorial diameter ratios showed the highest values in plants under water stress. In the roots, differences only in the cortex thickness being bigger in the non-irrigated treatment could be observed. Therefore, Siriema coffee plants under water stress show physiological, biochemical and anatomical modifications that contribute to the tolerance of this genotype to these conditions. Index terms: Coffee tree, ecophysiology, water stress, nitrate reductase. rESuMOEm razão do prognóstico de mudanças climáticas nos próximos anos, a compreensão do déficit hídrico e das respostas fisiológicas de plantas ao mesmo, torna-se uma importante condição para o desenvolvimento de tecnologias, como mecanismos que auxiliem as plantas a suportar períodos mais longos de seca, o que será essencial para a manutenção da produção mundial e brasileira. Neste estudo, objetivou-se avaliar aspectos ecofisiológicos e anatômicos além da atividade da redutase do nitrato em mudas de café Siriema submetidas a quatro tratamentos: irrigadas diariamente, não irrigadas, re-irrigadas 24 horas e re-irrigadas 48 horas após os diferentes períodos de estresse. A ausência de irrigação promoveu redução no potencial hídrico foliar, sendo mais acentuada a partir do nono dia de avaliação. A re-irrigação das mudas promoveu uma recuperação parcial do estado hídrico das plantas. Nas plantas não irrigadas observou-se um aumento na resistência estomatal e diminuição da transpiração, reduzindo a atividade da redutase do nitrato nas folhas. Nas raízes, houve um declínio na redutase do nitrato sob estresse hídrico. Ocorreram modificações na anatomia foliar apenas na espessura da epiderme da face adaxial e parenquimama paliçádico, sendo maior nas plantas controle. A densidade estomatal e razão diâmetro polar e equatorial demonstra...
The aim of this work was to use X-Ray Diffraction (XRD) as an analytical tool for characterization of Tommy Atkins mango kernel starch and fibres. The experiments were performed in a Rigaku diffractometer DMAXB with CuKα (λ = 1.5406 Å) at 40 kV and 40 mA, analysis speed of 1º (2θ).min -1 , with step scan of 0.05º, ranging between 2θ angle from 5º to 40º at 25 ºC to calculate Sega Crystallinity Index (CI). Mango starch presented diffraction peaks at 2θ = 11.62º, 15.12º, 17.14º, and 23.1º, which represents a typical type A starch pattern. In this structure, amylopectin molecules are fitted to a monoclinic unit cell. Raw fibres presented peaks at 2θ = 12º and 22º, typical for a cellulose I pattern. Mercerized and bleached fibres, and nanowhiskers presented peaks at 2θ = 15º, 22º, and 34º, typical for cellulose II pattern. Cellulose I has two unit cell structures: I a (triclinic) and I b (monoclinic). Cellulose II occurs just as a monoclinic unit cell. The diffraction peaks of Cellulose II around 2θ = 22º are narrower and higher than in Cellulose I. Moreover, the chemical treatment washes off amorphous components of the fibre, remaining crystalline structures. It was possible calculate the CI for raw fibres (29.4%), mercerized fibres (50.3%), bleached fibres (69.8%), and nanowhiskers (58.0%). Thus, the XRD technique is an important analytical tool for identifies the crystalline pattern of the mango kernel polysaccharides, as well as to quantify the Segal Crystallinity Index.
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