Manoel Bandeira de Albuquerque

Allelopathy, an alternative tool to improve cropping systems. A review

Known since ancient times, the phenomenon of allelopathy has recently received greater attention from researchers and farmers worldwide. Crop failures and low yields caused by the reseeding, overseeding, crop rotation and replanting of fruit trees in orchards are believed to be caused by allelopathic activity. Moreover, the expensive and environmentally impacting herbicides for weed control have motivated studies directed at developing cheaper, environmentally-friendly alternatives. Despite the difficulties in separating chemical interference from other mechanisms, more modern approaches have produced consistent and conclusive data on this topic. The release and dynamics of allelochemicals in the soil are discussed herein. Examples of allelopathic crops, the allelochemicals produced and their uses in cropping systems are also presented along with current research trends regarding allelopathy.

Growth evaluation and water relations of Erythrina velutina seedlings in response to drought stress

Erythrina velutina Willd. (common name: mulungu) is a deciduous, heliophyte found in the semi-arid region of northeastern Brazil. To evaluate the growth and water relations of mulungu seedlings in soils with different degrees of moisture content, an experiment was carried out under greenhouse conditions using four water treatments (100%, 75%, 50% and 25% of the field capacity- FC). Predawn (Ψpdw) and midday leaf water potential (Ψmdw), relative water content (RWC), plant height, number of leaves, stem diameter, leaf area (LA), specific leaf area (SLA), leaf area ratio (LAR), dry matter in different organs, biomass partitioning and root:shoot ratio were evaluated. No differences were detected between treatments for Ψpdw after 30 days; however, at midday, control plants and those under 75% FC underwent a greater reduction in Ψmdw than plants cultivated with 50% and 25% FC. After 90 days, only the plants under 50% FC exhibited a reduction in Ψmdw. RWC was reduced at midday, but there were no differences between treatments. Nearly all growth parameters were reduced due to water deficit, especially in the plants with 25% FC, as determined by the number of leaves, stem diameter, plant height, LA, SLA and dry mass in several organs. LAR and root:shoot ratio were not affected. Mulungu seedlings seem to have developed rusticity to overcome intermittent droughts with no change in the pattern of dry matter distribution. The maintenance of turgor pressure seems to be more associated to a reduction in the growth ratio than a reduction in leaf water potential.

Mudanças bioquímicas em genótipos de amendoim submetidos a déficit hídrico moderado

Five peanut genotypes, with different growth habits were submitted to moderate water stress in a greenhouse for seven days. Seeds were planted in 15-litre pots containing soil and a substrate (Plantmax®), both optimized for the crop. The adopted experimental design was completely randomized, using a 5 x 2 bi-factorial scheme(5 genotypes × 2 water treatments) with five replications. The enzymatic activities of SOD, CAT, APX and GPX were analyzed, as well as the carbohydrate, starch and proline. An increased activity was shown in SOD and CAT enzymes for all genotypes submitted to water stress, in both leaf and root, especially in the 55 437 and BR1 cultivars and also in LBM Branco line. Proline accumulation and reduced starch were verified in all stressed genotypes, but carbohydrate content was increased just in tolerant materials. Based on results, 55 437 and BR1 were more tolerant to water stress, followed by LBM Branco. The LBR Branco shows intermediate behavior and LViPE- 06 was more sensitive.

Drought and Its Consequences to Plants – From Individual to Ecosystem

Climate-change scenarios around the world indicate that many areas of the globe will in‐ crease in aridity. Thus, all living organisms will suffer from a water scarcity, especially plants, which do not have locomotive structures that allow them to move elsewhere when water and food becomes scarce. As a result, different terrestrial ecosystems (natural and ag‐ ricultural) will be severely affected and some may even collapse due to the extinction of plant species.

Leaf Area Estimate of Erythroxylum simonis Plowman by Linear Dimensions

This research aimed to determine an equation to estimate the leaf area of Erythroxylum simonis using the length and width of leaf blades. Two hundred leaf blades of this species were collected in Mata do Pau-Ferro, a State Park located in Areia, PB, Brazil. Regression analyses were used to determine the estimation equations. The linear, linear without intercept, quadratic, cubic, power and exponential statistical models were used. The criteria used for model selection were based on an examination of the coefficient of determination, the Akaike information criterion and standard error of the estimate. All the equations presented can be used to estimate the leaf area of E. simonis. From a practical point of view, the linear regression equation without intercept involving the product between length and width is recommended, using the equation Y=0.6426*LW, which corresponds to 64.26% of the product between length and width, with a coefficient of determination of 0.9936.

Morpho-physiological analyses of Allamanda blanchetii A. DC. seedlings under water deficit

The Allamanda blanchetii belongs to the Apocynaceae family, being an ornamental species popularly known as allamanda-roxa and is endemic to the Caatinga. The aim of this research was to evaluate the growth, gas exchange, relative water content, and stomatal density of A. blanchetii under water stress conditions. The experimental design was completely randomized with six levels of the maximum water holding capacity (MWHC) (100%, 80%, 60%, 40%, and 20%) with eight replications. Weekly, it was performed the evaluations of plant height and number of leaves. The results for water stress treatment in the A. blanchetii plants show that they develop better in the water levels of 100% and 80% of the MWHC, without presenting significant morphological and physiological changes. In turn, 20% of the MWHC does not allow the survival of the A. blanchetii plants. The water restriction negatively interfered in the gas exchange in the treatment of 60% and 40% of the MWHC. Therefore, it can be concluded that the A. blanchetii plants grow satisfactorily in 100% and 80% of the MWHC, ensuring the growth and survival during the drought period. The water availability to which the plants were submitted does not influence the total chlorophyll and relative water content of leaves. Gas exchanges are adversely affected at levels of water availability below 80% of the MWHC.