A B S T R A C TSalinity is one of the main environmental problems that negatively affect plant growth and metabolism, besides being one of the factors responsible for the decrease in the yield of crops, especially in arid and semiarid regions. Thus, the aim of this study was to evaluate the effects of soil salinity on the mineral nutrition of irrigated cowpea. The experiment was conducted in drainage lysimeters in a greenhouse, in a completely randomized design with seven treatments, one irrigated with freshwater (control) and six irrigated with saline water with different leaching fractions (5, 10, 15, 20, 30 and 40%) of the applied irrigation depth, with three replicates. The irrigation with saline water treatments did not affect significantly the contents of macronutrients and Na in the cowpea leaves, while the opposite behavior occurred with the micronutrients.Absorção de nutrientes pelo feijão caupi irrigado com água salina sob diferentes frações de lixiviação R E S U M OA salinidade constitui um dos principais problemas ambientais que afetam negativamente o crescimento e o metabolismo vegetal, além de ser um dos fatores responsáveis pelo decréscimo da produtividade das culturas, sobretudo nas regiões áridas e semiáridas. Objetivou-se com este estudo, avaliar os efeitos da salinidade do solo na nutrição mineral do feijão caupi irrigado. O experimento foi conduzido em lisímetros de drenagem, em casa de vegetação, no delineamento inteiramente casualizado com sete tratamentos constituídos de um irrigado com água doce (testemunha) e seis irrigados com água salina com diferentes frações de lixiviação (5, 10, 15, 20, 30 e 40%) da lâmina de irrigação aplicada e três repetições. A irrigação com água salina não influenciou de forma significativa as concentrações dos macronutrientes e de Na nas folhas do feijão caupi ocorrendo comportamento contrário com os micronutrientes.

A greenhouse study was carried out to evaluate the effects of increasing sodium chloride (NaCl) concentrations in a nutrient solution on growth-related morphophysiological and biochemical features during development of young plants of African mahogany (Khaya senegalensis). The NaCl concentrations were 0 mM (1.0 dS m-1), 20 mM (3.38 dS m-1), 145 mM (15.14 dS m-1), 270 mM (29.90 dS m-1), 395 mM (42.61 dS m-1) and 520 mM (53.60 dS m-1). Morphological features were negatively affected by increasing NaCl concentrations, except for plant height, which had no significant effect. Relative water content was not affected, whereas water potential decreased, suggesting osmotic adjustment. Whole plant dry mass was reduced, especially on roots, whose dry mass reduced up to 66% lower than in control. Regarding biochemical features, chlorophyll, chlorophyll content was reduced by salinity stress from 15.14 dS m-1, whereas reducing sugars, starch and proline contents were increased. We conclude that in the early development Khaya senegalensis is tolerant to salinity stress, since plant height was not affected, whereas the other morphophysiological parameters became significantly lower than the control only from moderate salinity levels. Salinity tolerance must have probably been favored by the osmotic adjustment provided by increased compatible osmolytes.

The quantification of the levels of photosynthetic pigments is of paramount importance, especially in the evaluation of the photochemical capacity of plants under saline stress. However, laboratory procedures for the titration of these pigments, such as chlorophyll, have expressive laboratory apparatus and specific reagents. This study aimed to evaluate a regression equation for correlation between SPAD index and photosynthetic pigments in African mahogany plants, Khaya senegalensis, under saline stress. The plants were cultivated in vases containing washed sand, in a greenhouse. Salinity was established by adding NaCl, with levels of electrical conductivity: 1.0 • 3.38 • 15.14 • 29.90 • 42.61 • 53.60 dS m ­-1 , in a completely randomized design (DIC) . The total chlorophyll contents were determined in the laboratory using a spectrophotometer and, in the plants, the SPAD index was quantified directly under the leaves. By regression analysis, through data evaluation with the STATISTICA program, the significant correlation between the SPAD index and total chlorophyll was expressed by the equation: Total chlorophylls = -41.0166 + 1.0338 EC, allowing this result to be direct quantification of the levels of photosynthetic pigments using the SPAD index.

No abstract

No abstract