Respostas ecofisiológicas e bioquímicas da erva-sal (Atriplex nummularia Lind.) ao estresse natalino

• Autor(a) principal: Costa, Naiara Araújo da
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/handle/riufs/6576
• topic: Plantas forrageiras; Biomassa; Atriplex; Sódio; Atriplex nummularia; Estresse salino; Trocas gasosas; Biomass; Forage plants; Sodium; Salt stress; Gas exchange; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA

The saltbush is an C4 species extremely tolerant to soils and saline waters and has good capacity to accumulate quantities of salts in their tissues, also serving as forage potential. Therefore, it is an excellent material for the identification of physiological and biochemical mechanisms involved in the resistance to salinity. The objective of this study was to evaluate the ecophysiological and biochemical responses of saltbush under increasing levels of NaCl. Plants were grown in pots kept in a greenhouse and irrigated every 2 days at concentrations of 0, 150, 300, 450 and 600 mM NaCl over time. Were determined biometric (height and stem diameter), gas exchange (photosynthetic assimilation of CO2 (A), stomatal conductance (gS), the internal concentration of carbon (Ci), transpiration (E) and vapor pressure deficit between leaf and air (DPVair-leaf)), the content of chlorophyll (Chl a, Chl b, Chl total and Chl a / b) and content of proline in leaves. The experimental design was completely randomized in a 5x4 factorial scheme, with five levels of salinity and for evaluation periods (0, 15, 30 and 45 days) with 5 replications. At 60 days evaluated the effect of levels 0, 150 and 300 mM NaCl on growth, fresh and dry biomass of shoot (stem+leaves) and root, gas exchange, content of chlorophyll, content of Na+, K+ and Na+/K+ in shoot and roots, and content of proline in leaves. The experimental design was DIC, with three levels of salinity and five replications. Until 45 days saltbush presented a stimulating growth at all levels of NaCl, and 0, 150 and 300 mM NaCl showed the highest values of height and stem diameter. As for the gas exchange saltbush presented an adaptive period of 15 days, followed by increase in photosynthetic assimilation. The saltbush accumulated more Na+ than K+, with greater accumulation in the shoot than in the root, to the 300 mM NaCl level, this is the salinity level that the highest yield of fresh biomass (46,38 g) and dried (19,69 g). Increased salinity promoted accumulation of proline, whose highest concentration (3,11 micromol g-1 FM) was observed in 600 mM NaCl treatment. At 60 days the salt stress induced no significant differences in plant growth, but promoted reduction of photosynthetic assimilation and increased internal carbon concentration. After 60 days, saltbush accumulated Na+ in shoot with growth and biomass production was enhanced up to 300 mM NaCl level. Increased levels of salinity reduces the photosynthetic assimilation of the saltbush, but did not significantly affect the production of chlorophylls. In response to salinity saltbush has increased the concentration of proline in their leaves. With increasing salinity, the saltbush develops physiological and biochemical mechanisms to ensure its growth, with the 300 mM NaCl level which favors its maximum production.