Anderson Lopes Peçanha

Determinação do coeficiente cultural (Kc) do feijoeiro (Phaseolus vulgaris L.), em Campos dos Goytacazes, RJ

The evapotranspiration of a crop is one of the main information required for proper irrigation management and to develop an efficient water usage plan. Among the methods to estimate the amount of water that is consumed by plants, the use of crop coefficients (Kc), associated with estimates of the reference evapotranspiration (ETo), stands as one of the most promising. This work aimed to deterime the values of Kc for different phenological phases of common bean plants (Phaseolus vulgaris L.) of the cultivar UENF-47. Determination of Kc values was performed using a weighing lisimeter and results were compared with values obtained through the FAO 56 standard. Results showed that the adjustment equations proposed by Allen et al. (1998) were adequate for fitting the values of Kc obtained in this experiment. It has been shown that the crop coefficients for phenological phases 3 and 4 proposed by Allen et al. (1998) are adequate for the conditions of crop growth observed in Campos dos Goytacazes, Rio de Janeiro state, Brazil, during the autumn/winter period.

Photosynthesis and cell respiration modulated by water deficit in grapevine (Vitis vinifera L.) cv. Cabernet Sauvignon

Winegrape productivity and quality has been related to the regulated deficit irrigation, with important implications for the plant bioenergetics. When water deficit is imposed to grapevine plants, alterations in overall photosynthesis and cell respiration are observed. The aim of this study was to assess the modulations promoted by water stress on photosynthesis and respiration in leaves of the cv. Cabernet Sauvignon (cv. CS) for better understanding the physiological responses related to its drought tolerance and quality improvement under water deficit. For this purpose, measurements of photosynthetic efficiency, leaf water potential, gas exchange and O2 consumption were carried out. Leaf water potential, photosynthesis, stomatal conductance, transpiration and internal carbon concentration were significantly reduced upon stress, suggesting that plants of cv. CS present higher water use efficiency (AN/E) and lower carboxylative capacity (AN/Ci) under this condition. On the other hand, cell respiration increased more than 70 % as estimated by the increase of O2 consumption measured 12 days after suspension of irrigation. Most of this effect was related to a four-fold increase of the mitochondrial alternative oxidase (AOX) activity. These data indicate a key role for the AOX pathway in the physiological responses of grapevines to water deficit, and it implies that analyses of the AOX activation patterns should be useful for programs aiming to improve the consistency of fruit production and quality of winegrape cultivars by regulated deficit irrigation.

Estado nutricional do coqueiro cultivado em solos submetidos a diferentes níveis de compactação e umidade

Com o objetivo de avaliar o efeito da compactacao e da umidade do solo na absorcao de nutrientes pelo coqueiro anao-verde, implantou-se um experimento em casa de vegetacao em Campos dos Goytacazes, RJ. O delineamento experimental utilizado foi em blocos casualizados com tratamentos distribuidos em esquema fatorial (2 x 4 x 4), com tres repeticoes, sendo duas classes de solo (Argissolo Amarelo Distrocoeso latossolico e Cambissolo Haplico Tb Distrofico tipico gleico), quatro niveis de compactacao em subsuperficie e quatro condicoes hidricas. Os solos atuaram de forma diferenciada no suprimento de nutrientes, sendo determinado o teor foliar de Mg e Cu mais elevado nas plantas cultivadas no Cambissolo e os de K e Ca nas cultivadas no Argissolo. O incremento da umidade do solo alterou a disponibilidade de nitrogenio no Argissolo fazendo com que as plantas cultivadas nos maiores niveis de umidade apresentassem teor foliar mais elevado de N. Tambem no Argissolo a compactacao afetou a absorcao de manganes e cloro observando-se, nas plantas cultivadas nos niveis mais elevados de compactacao, teor foliar maior de Mn e menor de Cl.