| Abstrakt: |
Schizolobium parahybavar. amazonicum(Huber ex Ducke) is an Amazonian native species with great economic importance and wide natural distribution, being the most commonly used tree in Brazilian silviculture. Imbalance zinc (Zn) application causes negative impacts on photochemical efficiency, gas exchange, antioxidant responses, nutritional status and growth. However, there are still no studies focused on Zn fertilization and better dose response in young S. parahybaplants available in the literature. The aim of this research was to understand how zinc (Zn) supply modulates biomass accumulation, nutritional status, chlorophyll afluorescence, gas exchange, photosynthetic pigments and stress indicators in young S. parahybaplants. The experiment was randomized into five treatments (0.2, 2, 500, 1000, and 2,000 μM Zn). The highest biomass accumulation was observed in plants treated with 500 μM Zn. Leaf dry matter (LDM), root dry matter (RDM) and stem diameter (SD) were 70%, 67% and 28% lower in plants under Zn deficiency (0.2 µM), as compared with the 500 μM Zn treatment, respectively. Plants exposed to Zn excess (2,000 µM) exhibited minor values in LDM (32%), RDM (48%) and SD (25%), in comparison with better treatment (500 μM Zn). Light absorption and gas exchange suffered deleterious effects under limited Zn supply (0.2 μM), being confirmed by the lower effective quantum yield of PSII photochemistry (17%), electron transport rate (14%) and net photosynthetic rate (54%), comparing with 500 μM Zn. Stress indicators (superoxide and hydrogen peroxide) were increased after Zn stress and low concentrations of nutrients and chlorophylls were detected in plants exposed to deficiency or excess of Zn. This is the first study measuring chlorophyll afluorescence in S. parahybaplants, in which it demonstrated that 500 μM Zn was the better dose response, inducing increases in biomass and stimulating the photosynthetic machinery. |
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