SUMMARYFew studies in Brazil have addressed the need for micronutrients of physic nut focusing on physiological responses, especially in terms of photosynthesis. The objective of this study was to evaluate the effects of omission of boron (B), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) on Jatropha curcas L.. The experimental design was a randomized block with four replications. The treatments were complete solution (control) and solution without B, Cu, Fe, Mn, and Zn. We evaluated the chlorophyll content (SPAD units), photosynthetic rate, dry matter production and accumulation of micronutrients in plants, resulting from different treatments. The first signs of deficiency were observed for Fe and B, followed by Mn and Zn, while no symptoms were observed for Cu deficiency. The micronutrient omission reduced the dry matter yield, chlorophyll content and photosynthetic rate of the plants differently for each omitted nutrient. It was, however, the omission of Fe that most affected the development of this species in all parameters evaluated. The treatments negatively affected the chlorophyll content, evaluated in SPAD units, and the photosynthetic rate, except for the omission of B. However this result was probably due to the concentration effect, since there was a significant reduction in the dry matter production of Bdeficient plants.Index terms: Jatropha curcas L., nutritional status, dry matter, IRGA, SPAD.(1) Received for publication in November 22, 2012 and approved in June 7, 2013. (2)
* RESUMO -As maiores exigências em nitrogênio (N) e cálcio (Ca) têm sido relatadas para as espécies da família Euforbiaceae. Objetivou-se avaliar o suprimento combinado de doses de N e Ca e seu efeito na avaliação do estado nutricional da Jatropha curcas, por meio das diagnoses visual, foliar e bioquímica (redutase do nitrato RNO 3 -e o teor de clorofila), além de determinar o rendimento de biomassa e os acúmulos de N e Ca durante o crescimento inicial das plantas. Foram utilizadas as doses 2; 9; 16; 23 e 30 mmol L -1 de N e 0,5; 1,75; 3,0; 4,25 e 5,5 mmol L -1 de Ca na solução nutritiva. As concentrações de N, Ca e K, nas folhas utilizadas para diagnose, foram alteradas pelas combinações de doses de N e Ca, enquanto que as concentrações de Mg foram alteradas somente pelas doses de Ca. O aumento das concentrações de N e Ca na solução resultou em incrementos na área foliar e na produção de biomassa de folhas em 400% e 245%, respectivamente. Em média, as quantidades de N e Ca acumuladas nas folhas corresponderam a 29% e 39% do total acumulado nas plantas. O rendimento de biomassa guarda relação direta com a atividade da RNO 3 -e teor de clorofila, sendo a faixa de concentração de N nestas folhas de 43 a 45 g kg -1 para a máxima produção. O nitrogênio promove maior impacto no rendimento de biomassa das plantas, todavia, os efeitos são mais expressivos com o aumento da absorção de Ca.Palavras-chave: Área foliar. Diagnose foliar. Jatropha curcas. Redutase do nitrato.ABSTRACT -Higher nitrogen (N) and calcium (Ca) requirements than other macronutrients in Euphorbiaceous species have been pointed out in the literature. Thus, the objective of this work was evaluate the effects of N and Ca combination rates on the visual deficiencies of both nutrients, on the macronutrient status, chlorophyll content and nitrate reductase activity (RNO 3 -) taken on the recent expanded leaves of Jatropha curcas, as well as to evaluate N and Ca uptake and biomass yield during early plant growth, subjected to 2; 9; 16; 23 e 30 mmol L -1 N rates and 0.5; 1.75; 3.0; 4.25 e 5.5 mmol L -1 Ca rates, in the nutrient solution. Nitrogen, Ca and K concentrations on the recent expanded leaves were changed by N and Ca rates, whereas leaf-Mg concentrations ranged only by Ca supply. Increasing N and Ca rates in solution led to increased leaf area and the leaf biomass yield by 400% and 245%, respectively. On average, N and Ca taken up on leaves accounted for 29% and 39% of the plant uptake. Biomass yield is directly related to RNO 3 -activity and chlorophyll content, and the range of N concentration in these leaves related to highest plant dry matter production is 43-45 g kg -1. In conclusion, N supply causes greater impact on the plant biomass yield; however, the effects are more relevant with increased Ca uptake.
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