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)

The description of physiological disorders in physic nut plants deficient in nitrogen (N), phosphorus (P) and potassium (K) may help to predict nutritional imbalances before the appearance of visual symptoms and to guide strategies for early nutrient supply. The aim of this study was to evaluate the growth of physic nuts (Jatropha curcas L.) during initial development by analyzing the gas exchange parameters, nutrient uptake and use efficiency, as well as the nitrate reductase and acid phosphatase activities and polyamine content. Plants were grown in a complete nutrient solution and solutions from which N, P or K was omitted. The nitrate reductase activity, phosphatase acid activity, polyamine content and gas exchange parameters from leaves of N, P and K-deficient plants indicates earlier imbalances before the appearance of visual symptoms. Nutrient deficiencies resulted in reduced plant growth, although P- and K-deficient plants retained normal net photosynthesis (A), stomatal conductance (g) and instantaneous carboxylation efficiency (k) during the first evaluation periods, as modulated by the P and K use efficiencies. Increased phosphatase acid activity in P-deficient plants may also contribute to the P use efficiency and to A and gs during the first evaluations. Early physiological and biochemical evaluations of N-, P- and K-starved plants may rely on reliable, useful methods to predict early nutritional imbalances.

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Sugarcane has marked genotypic variation related to nutrient use efficiency, which in turn the approach of this subject in scientific research prioritizes studies related to nitrogen (N) and phosphorus (P), but due to the essentiality of potassium (K) as a nutrient, and its importance in the Brazilian economy, researches related to K use efficiency can help the development of efficient genotypes, which, because the K water relation functions in plants may have a direct relation in the water use efficiency. In the first experiment were evaluate the changes in morphological and physiological sugarcane genotypes (SP90-3414 and SP83-2847) promotes by the reduction of K concentration, the parameters were quantifying the leaf area; root system morphology (total length and total surface area of roots); biomass of roots and shoots; K concentration and accumulation in plant tissues; total soluble and reduced sugars percentage; activity of the enzyme nitrate reductase; leaf water potential and gas exchange parameters. The K concentrations used in the nutrient solution were 1 and 6 mmol L-1 , distributed as experimental design of randomized complete block design, using a factorial 2 x 2 (two K rates x two sugarcane genotypes), with five replications. The rates caused differences in the K uptake efficiency by cultivars, triggering positive changes in their accumulation in plant tissues and the morphological and physiological parameters. The second experiment were to evaluated the influence of water deficit on morphological and physiological parameters of the plants and to study the behavior of these parameters according to the increase of the available K concentration. The analysis aimed to evaluate the water relations in plants and the water status interference in the gas exchange process, as well as relating the parameters of the K use efficiency with the efficiency of water use. The experiment was conducted in pots containing 8 dm 3 of soil, the experiment was also conducted in a randomized block design, using a factorial 2 x 2 x 2 (two K rates x two water regimes x two sugarcane cultivars), and the K rates used was 1 and 6 mmol c dm-3 of soil, water regimes was 70% and 20% of field capacity and the genotypes were the same as the first experiment. The results shows improvements in water and gas exchange parameters of cultivars developed in high-level K and subjected to water deficit, showing a positive relationship between potassium fertilization and sugarcane plant resistance to adverse water condition. On average, the highest water use efficiency (WUE) of SP83-2847 tolerant genotype may result from potassium use ufficiency (KUtE).