Higher plants display different adaptive strategies in photosynthesis to cope with abiotic stress. In this study, photosynthetic mechanisms and water relationships displayed byJatropha curcasL. (physic nuts) andRicinus communisL. (castor bean), in response to variations in environmental conditions, were assessed.R. communis showed higher CO2 assimilation, stomatal and mesophyll conductance thanJ. curcas as light intensity and intercellular CO2 pressure increased. On the other hand,R. communis was less effective in stomatal control in response to adverse environmental factors such as high temperature, water deficit and vapor pressure deficit, indicating lower water use efficiency. Conversely,J. curcas exhibited higher photosynthetic efficiency (gas exchange and photochemistry) and water use efficiency under these adverse environmental conditions.R. communisdisplayed higher potential photosynthesis, but exhibited a lowerin vivo Rubisco carboxylation rate (Vcmax) and maximum electron transport rate (Jmax). During the course of a typical day, in a semiarid environment, with high irradiation, high temperature and high vapor pressure deficit, but exposed to well-watered conditions, the two studied species presented similar photosynthesis. Losing potential photosynthesis, but maintaining favorable water status and increasing non-photochemical quenching to avoid photoinhibition, are important acclimation mechanisms developed byJ. curcas to cope with dry and hot conditions. We suggest thatJ. curcas is more tolerant to hot and dry environments thanR. communis but the latter species displays higher photosynthetic efficiency under well-watered and non-stressful conditions.

O objetivo deste trabalho foi avaliar alterações nas trocas gasosas e nos conteúdos de carboidratos e compostos nitrogenados, em pinhão-manso (Jatropha curcas) irrigado com águas residuária e salina. Empregou-se o delineamento em blocos ao acaso, com quatro tratamentos e quatro repetições: irrigação plena com água de abastecimento a 0,6 dS m-1 (controle); irrigação plena com água salinizada a 2,4 dS m-1 (SAL); e irrigação com água residuária de esgoto, plena (R100) e a 50% da capacidade de campo (R50). O tratamento R50 reduziu fortemente as trocas gasosas e a área foliar, comparado ao controle, seguido pelos tratamentos SAL e R100. A redução na fotossíntese diminuiu o nível de sacarose nas folhas, nos quatro tratamentos. Os teores de açúcares solúveis aumentaram nos tratamentos R50, SAL e R100, enquanto o conteúdo de amido permaneceu praticamente inalterado. Os conteúdos de prolina e glicina betaína aumentaram nos três tratamentos, mas a última foi mais importante, em termos quantitativos, como protetor celular e osmótico. A irrigação plena com água residuária induz efeitos similares aos causados pela irrigação com água salina. A irrigação limitada com água residuária causa estresse agudo às plantas, provavelmente pela combinação de deficiência hídrica e acúmulo de solutos no solo.

The objective of this work was to evaluate the changes in gas exchange and in the contents of carbohydrates and nitrogen compounds in physic nut (Jatropha curcas) irrigated with wastewater and saline water. The experiment was carried out in a randomized block design, with four treatments and four replicates: irrigation with tap water at 0.6 dS m-1 (control); full irrigation with saline tap water at 2.4 dS m-1 (Salt); and irrigation with wastewater at full (W100) or at 50% field capacity (W50). The W50 treatment remarkably reduced gas exchange and leaf area in comparison to the control, followed by Salt and W100 treatments. Reduction in photosynthesis lowered leaf-sucrose content in the four treatments. Total soluble sugar contents increased in W50, Salt, and W100 treatments, while starch content remained almost unaltered. Proline and glycine betaine contents increased in these treatments, but the latter was quantitatively more important as osmotic and cellular protector. Full irrigation with wastewater induces similar effects to the ones caused by irrigation with saline water. Irrigation with limited amounts of wastewater caused an acute stress to plants, probably due to a combination of water deficit and solute accumulation in the soil.

O objetivo do trabalho foi avaliar os efeitos de combinações de nitrato e amônio no meio, na acumulação de compostos nitrogenados e carboidratos, na presença e ausência de salinidade em plantas de sorgo. Sementes do genótipo CSF 20 foram cultivadas em casa de vegetação, em solução nutritiva com três concentrações de nitrato e amônio (100% NO3-: 0% NH4+, 75% NO3-: 25% NH4+ e 0% NO3-: 100% NH4+), na presença e ausência de salinidade. A salinidade reduziu a concentração de nitrato nas folhas e colmo, nos tratamentos 100:0 e 75:25. O amônio acumulou-se mais nas plantas com NaCl, nas folhas e colmo. Os teores de aminoácidos livres totais nas folhas não se alteraram, mas, no colmo, aumentaram na presença de sal e aumento do amônio. A concentração de prolina livre nas folhas e colmo elevou-se nas plantas sob salinidade. O conteúdo de nitrogênio total foi maior nas folhas, entretanto não houve grandes alterações com a presença do sal. A concentração de carboidratos solúveis totais foi maior nas plantas tratadas com sal, exceto no colmo 0:100. Nas folhas, o teor de sacarose foi reduzido na presença do NaCl e aumento de amônio, enquanto, no colmo, foi maior no tratamento 75:25 com NaCl. O teor de amido não sofreu alterações com as diferentes combinações nas formas de N e salinidade. Conclui-se que combinações de NO-3 e NH4+ no meio afetam a acumulação de compostos nitrogenados e carboidratos em folhas e colmo, com presença ou ausência de salinidade, em plantas de sorgo forrageiro.

The objective of this study was to evaluate the effects of combinations of nitrate and ammonium in the medium, on the accumulation of nitrogen compounds and carbohydrates, in the presence and absence of salinity in sorghum plants. CSF 20 genotype sorghum seeds, were grown in the greenhouse and supplied with a nutritive solution at three different concentrations of nitrate and ammonium (100% NO3-: 0% NH4+, 75% NO3-: 25% NH4+ e 0% NO3-: 100% NH4+) both in the presence and absence of NaCl. Salinity reduced the nitrate concentration in both leaves and stalks in treatments at 100:0 and 75:25. The accumulation of ammonium was higher in those plants, in both leaves and stalk, in the presence of NaCl. The levels of free amino acids in the leaves showed no change, whereas those in the stalk increased in the presence of salt and with the increase of ammonium. The concentration of free proline in both leaves and stalk was higher in plants under salinity. The total nitrogen content was higher in the leaves without, however, showing much change in the presence of salt. The concentration of total soluble carbohydrates was higher in those plants treated with salt, except in the stalk 0:100. Sucrose levels in the leaves were lower in the presence of NaCl and the increase in ammonium, while they were higher in the stalk at 75:25 NaCl. The starch content did not alter much with the different levels of nitrogen and salinity. It is concluded that NO-3 and NH4+ combinations in the medium affect the accumulation of nitrogen compounds and carbohydrates in the leaves and stalks of sorghum plants, both in the presence and absence of salinity.

Amostras de solo e de cavaco de bambu (Bambusa vulgaris) com 11 meses de idade (rebrota) foram coletadas em sítios comerciais localizados no Estado da Paraíba, com o objetivo de avaliar a produção de biomassa de colmos e galhos e o conteúdo e exportação de macronutrientes. O solo foi analisado quanto à fertilidade, e nos cavacos foram efetuadas determinações analíticas dos macronutrientes minerais. A quantidade exportada de cada nutriente foi calculada pela multiplicação do seu teor no cavaco, pela produtividade de cavacos de cada talhão. A produtividade dos cavacos, em toneladas por hectare, foi estimada através da multiplicação da produtividade real, obtida em cada parcela, pelo fator de conversão oriundo da relação entre 1 ha e a área da parcela. O solo da fazenda Mamoaba mostrou teores de Na, K, P, Fe, Zn e Mn superiores aos da fazenda Garapu. O teor de matéria orgânica no solo seguiu esta ordem: Garapu 2 > Garapu 1 > Mamoaba. A fazenda Garapu apresentou maior produtividade do que a fazenda Mamoaba, provavelmente devido aos maiores índices pluviométricos. Os cavacos analisados exportaram aproximadamente duas vezes mais K do que N, sendo P e S os macronutrientes menos exportados pela cultura. Os teores dos macronutrientes acumulados nos cavacos, bem como a quantidade exportada, seguiram a mesma ordem em todos os sítios estudados: K>N>Ca>Mg>P>S. Os programas de adubação da espécie de bambu estudada devem priorizar o fornecimento de nitrogênio, potássio e cálcio.

Samples of soil and bamboo chips (Bambusa vulgaris) 11 months in age (regrowth) were collected at commercial sites, located in the state of Paraíba (Brazil), aiming to evaluate the stem and branch biomass production, and the content and export of nutrients. The soil was analyzed for fertility and chips had analytical determinations made of mineral nutrients. The export quantity of each nutrient was calculated by multiplying the amount contained in the chip, by the chip productivity of each plot. The chip productivity, in tons per hectare was estimated by multiplying the measured yield of each plot, by the conversion factor derived from the relationship between the area of one hectare and the area of each plot. The soil of the Mamoaba farm showed Na, K, P, Fe, Zn and Mn content higher than the soil from the Garapu farm. The content of organic matter in the soil followed this order: Garapu 2 > Garapu 1 > Mamoaba. The Garapu farm had higher productivity than the Mamoaba farm, probably due to the higher rainfall at Garapu farm. The analyzed chips exported roughly twice as much K than N. P and S were the macronutrients less exported by bamboo. The macronutrient contents and exportations followed the same ratio for all sites studied: K>N>Ca>Mg>P>S. The fertilization programs for the studied species of bamboo have to prioritize the supply of nitrogen, potassium and calcium.