José Elenildo Queiroz

Effects of NaCl-salinity on growth and inorganic solute accumulation in young cashew plants

Os efeitos da salinidade sobre o crescimento e acumulacao de solutos inorgânicos foram avaliados em plantas de cajueiro (Anacardium occidentale L.), com 30 dias de idade, cultivadas em diferentes doses de NaCl, por 8 dias (curta duracao) e 40 dias (longa duracao). A producao de massa fresca (MF) da parte aerea, apos 40 dias, foi reduzida, aproximadamente, 25 e 75% sob 50 e 100 mol m-3 de NaCl, respectivamente. Nas raizes, a producao de MF nao foi afetada em 50 mol m-3 de NaCl, entretanto decresceu 30% em 100 mol m-3 de NaCl. No experimento de curta duracao, a concentracao de K+ nos diferentes tecidos foi similar aquela das plantas controle, enquanto que, no experimento de longa duracao, a concentracao de K+ foi fortemente reduzida, principalmente nas raizes. Em resposta ao tempo e a salinidade crescente, as concentracoes de Na+ e Cl- atingiram niveis toxicos nas folhas o que levou, a partir do quarto dia do estresse salino, ao surgimento de sintomas tipicos de toxicidade por estes ions. Em consequencia, as plantas de cajueiro nao foram habeis em regular suas funcoes metabolicas e fisiologicas nessas condicoes adversas de crescimento.

Growth and total-N content of Prosopis juliflora (SW) D. C. are stimulated by low NaCl levels

In this study the early effects of salinity on growth, total N and ion accumulation and partitioning in Prosopis juliflora (common name algaroba) were studied with 30-day-old plants grown for 8 days in aerated nutrient solution (NS) free of (control) or supplied with 25, 50, 75 and 100 mmol.L-1 NaCl. Plants grown in 25 and 50 mmol.L-1 NaCl accumulated a total dry mass (DM) and shoot N content greater than the control. However, at 75 and 100 mmol.L-1 NaCl such parameters were diminished. Whole plant transpiration rates were higher with 25 and 50 mmol.L-1 NaCl and lower with 75 and 100 mmol.L-1 NaCl. Salinity did not influence shoot (80%) and root (70%) water content (WC) but reduced the K+ content of shoot while that of root was not affected. Increasing external NaCl concentrations increased K+/Na+ ratios of both plant parts. The data support the hypothesis that increase in transpiration rates and in shoot total N may account for growth stimulation of algaroba under mild salinity.

Spatial variability of soil salinity in an alluvial soil of the semi-arid region of Paraíba state

The objective of this work was to study the spatial variability of pH of saturation paste (pHsp), the electrical conductivity of saturation extract (ECe) and the exchangeable sodium percentage (ESP) in an alluvial salt affected soil. Soil samples were collected in 0 - 20, 20 - 40 and 40 - 60 cm depths, in an area of the Irrigation Project of Capoeira, located in Sao Jose do Bonfim - Paraiba (Brazil), following a systematic scheme of sampling in a 10 x 15 m mesh. The data were analyzed through the descriptive statistics and geostatistics. Low variability was observed for the pHsp (CV 60%). Spherical and gaussian models were adjusted to the experimental semivariograms of the variables that presented a spatial dependence structure. Structures of spatial dependence, with range varying from 20 to 40 m were observed. The maps of isohypsas of the combination of ECe and ESP allowed the visualization of the pattern of the salinity and sodicity variability, constituting a tool for the definition of soil management and reclamation of the affected area. Key words: salinization, exchangeable sodium percentage, geostatistics

Estimativa da porosidade drenável de um solo de várzea a partir da tensão da água no solo

An alternative way to assess the drainable porosity as a function of soil-water tension, from the soil-water retention curve (Van Genuchtens model), is presented for data of a clayey holm gley soil of the county of Piracicaba, SP, Brazil. Soil-water retention curves were determined using undisturbed soil samples. The analysis of the results has shown that the data variability was mainly due to random causes. Statistical indexes used to verify the degree of fitting of the experimental data to the proposed model, have shown that the model can be used to estimate the drainable porosity from the empirical parameters of the Van Genuchten model.