This study had the objective of surveying the occurrence of tubers in native imbu (Spondias tuberosa) trees in the Northeast of Brazil. It was carried out in 36 native trees in the Caatinga area of the communities of Sitio Papagaio (Juazeiro-BA), Saco Farm (Jaguarari-BA) and Alto do Angico (Petrolina-PE), from August 2000 to November 2002. In each community, twelve plants were randomly selected for tuber extraction. The following variables were analyzed: plant height, trunk diameter at soil level, canopy diameter, as well as number and total weight of tubers per tree. In the community of Sitio Papagaio, in average, 978.42 tubers per tree were collected, with a total weight of 1731.2 kg. In the community of Saco Farm, in average, 1011.58 tubers were collected, with a total weight of 1820.13 kg. In the community of Alto do Angico, in average, 731.58 tubers per tree were collected, with a total weight of 1370.09 kg. The occurrence of tubers per tree in the communities was, in average, 907.19, with a total weight of 1352.12 kg per tree.

The physiologic activity of two corn varieties regarding nitrogen accumulation and remobilization in the vegetative phase was evaluated by the activity of the nitrate reductase enzyme (NR), and NO3 - contents of the N-amino and soluble sugars in leaves, hems and stems of the plants. The varieties were selected according to their agricultural characteristics: BRS 4157 (Sol da Manhã), an improved variety used in familial agriculture and BRS 1010, an exotic variety, a simple hybrid used in extensive agriculture. The plants were cultivated in a greenhouse, in pots containing a Red-Yellow Argissol submitted to two doses of N-NO3 - (130 and 1300 mg of N per pot). Harvests were made at the first two stages of the vegetative development, at 32 and 60 days after germination (DAG). The Sol da Manhã variety, efficient in nitrogen use, adapted itself to the condition of low nitrogen due to its higher capacity in accumulating NO3 - in the leaves in the first development stage, and remobilizing it during the second stage. This resulted in a higher free amino-N concentration in the leaves and hems when compared to the simple hybrid BRS 1010, described as a high potential in productivity under low nitrogen conditions.

The objective of this work was to evaluate the effect of cut-time on lemon grass essential oil yield and on its constituent citral contents. A completely randomized design with four replications was used. Six cuttimes were studied: 7:00, 9:00 and 11:00 AM, 1:00, 3:00 and 5:00 PM. The analyzed variables were essential oil yield and relative citral contents. The highest essential oil yield was obtained when cut occurred at 7:00 AM. The highest citral contents was obtained when cut occurred at 1:00 PM, but was not statistically different from those obtained at 7:00, 9:00 and 11:00 AM, and 3:00 PM. Lemon-grass must be harvested between 9:00 and 11:00 AM in order to obtain maximum essential oil yield and maximum citral contents.

The withdrawal of the natural vegetation in order to implement an agriculturist system provokes disequilibrium in the soil. This study had as objective: evaluate changes in the chemical and physical characteristics of the ground and in the total organic carbon level of a ground that has experienced different systems of use: remainder of Atlantic Bush, cacao (Theobroma cacao), and pasture (Brachiaria decumbens). For each use, samples were collected, in the depths of 0 - 10 and 10 - 20 cm. The chemical and physical analyses had been proceeded, and the determination of the total organic carbon, nitrogen and match in the soil. The substitution of the natural vegetation for the cacao and pasture systems caused changes in the level of clay in the layer of 0 ¿ 10 cm and in the levels of clay and silte in the second layer 10 - 20 cm. To the chemical characteristics evaluated (0-10 cm), it was observed that the levels of Ca+2, Mg+2 and P were higher, and in the cacao system, while the pasture showed higher pH and levels of K+ and lower CTC. The attributes Al+3 and m decreased and V increased. 10-20cm the cacao and pasture systems showed changes just related to the level of Ca+2, and for the cacao system,higher P level. The TOC and chemical attributes in the second layer showed significant correlations just for the pasture area.

Among ten valid species within Rotylenchulus genus, R. reniformis is the economically most important. Polyfagous, the reniform nematode has been detected associated to high value crops in Brazil. However, variability among or within Rotylenchulus spp. populations has been poorly understood and studied. Identification of Rotylenchulus species is based on morphological characters of immature females and presence of males, but there is a lack of biochemical researches. The objectives of this study were to morphometrically characterize one R. reniformis population associated to commercial melon (Cucumis melo) crop grown in Baraúnas municipality, Rio Grande do Norte State; to compare L, V and s mean values to the other populations characterized as R. reniformis, from different Brazilian and North American states, and African countries; to identify the parasitic race and to develop a protocol to define the a-esterase phenotype. The results confirmed the specific population identification focused in this research which confidence interval mean values of L, V and s enclosed mean values from the other populations. The Baraúnas-RN population was characterized as race A. The used protocols did not allow to characterize an a-esterase phenotype for R. reniformis.

The objective of this work was to study the influence of the seeds storage period of the Imbu Tree (Spondias tuberosa Arruda) in the germination percentage and germination velocity index. The study was carried out from January to December 2004 in a greenhouse with 50% shadowing screen, under room temperature, at Embrapa Tropical Semi-Arid, Petrolina, Pernambuco State, Brazil, in a randomized complete block design, with six treatments and four replications. The treatments consisted of seeds harvested in six different crops. The germination percentage and germination velocity index were evaluated at 30, 60, 90 and 120 days after sowing through daily counts. The seeds of 2001 and 2002 crops had the best performance in terms of emergence and germination velocity index.

Seedling production is an important step for the tomato (L. esculentum) production system, being sometimes limited by cost and quality of the substrates used for this purpose. Use of agro-industrial residues, alone or in mixtures, may help reduce this problem. The potential of different mixtures of substrate including coconut dust treated with nitrogen, phosphorus and potassium (PC), commercial substrate TropstratoÒ and organic compound (CO) were evaluated in order to obtain the best source and combinations of substrates. These materials were used alone or in volumetric basis mixtures at the proportions of PC+SC (1:1); PC+CO (1:1) and PC+SC+CO (1:1:1), for seedling production of tomato cv. Salada. The randomized block design was used, with six treatments and six replications. Obtained data were aerial dry matter (MS), emergence speed index (IVE), colon diameter (DC), leaf number (NF) and seedling height (AP). The best results were obtained for CO and PC+CO. CO performance probably is due to its higher nutritional value, once its physical characteristics do not differ from the remaining treatments, especially when compared to SC and PC. CO was the best substrate for tomato seedling production, and its addition to PC enhanced the performance. The use of organic residues for tomato seedling substrate composition is an economic option which may reduce production costs, and represents an alternative for recycling and subproduct usage in agro-industry.

This work aimed to evaluate nodular occupancy rate of rhizobium strains inoculated in different cowpea accesses (Vigna unguiculata (L.) Walp) from Brazil, USA and Nigeria and their relationship with the symbiotic specificity. The identification of strains in nodules was done using Enzyme-Linked ImmunoSorbent Assay (Indirect-ELISA). It was observed that the nodule number and weight were influenced by the origin of cowpea accesses. The inoculation was able to promote a significant increase in the number of nodules occupied by serogroup of inoculant strain. In agreement with the cowpea accesses origin, the Brazilian accesses presented the largest of nodule occupancy rates, followed by those of Nigeria and USA. The largest occupation percentage, in 6 of the 10 tested cowpea, was due to the innoculation with the BR 3273 strain, and the smallest one was due to BR 3269 strains, in 8 of the 10 cowpea accesses. These data suggests that specificity exists between rhizobium inoculant strains and cowpea accesses.

Natural regeneration depends on a series of environmental factors, which determine seed and seedling bank composition, and plant community structure of a site. Jurema preta (Mimosa tenuiflora (Willd) Poiret) is a pioneer legume tree that colonizes degraded sites of the Caatinga and produces a great number of seeds in several months of the year. In despite of its abundance, there is little information on the dynamics of jurema preta natural regeneration. Thus, a study was carried out to find out if seed germination and plantule survivorship under jurema preta canopy are affected by the annual April or July pruning of fine branches of a few jurema preta plants in a native Caatinga thicket submitted to continuous cattle browsing. Data analyses show that seed germination occurs in the beginning of the rainy season, and that in this period of moisture availability, plantule bank is composed by 17 to 58 thousand seedlings/ha. This number decreases during the rainy season, until it reaches a minimum of 3.7 to 7.5 thousand seedlings/ha, at the end of the dry season, in an ecological strategy of recurrent annual colonization. April or July pruning shows no consistent effect on jurema preta natural regeneration in areas submitted to bovine browsing, although plantule number was temporary and positively affected by pruning in one of the experimental site at the peak of the rainy season.

This work had as objective to evaluate the emergency and the survival of seedlings of imbu tree (Spondias tuberosa Arruda) in caatinga. The assay was carried through of January of 2001 the December of 2004 with 37 plants of imbu tree, selected to perhaps in area of caatinga of the Embrapa Semi-Árido, Petrolina - PE. In each plant four quadrants of 1 m2 had been demarcated randomized below of the pantry for counting of the emergency and survival of seedlings. The comments had been carried through to each 15 days in the rainy station and 30 days in the dry station. A rain gauge was installed in the area of the experiment for attainment of the values of the occurred precipitation during the period of evaluation. The biggest indices of emergency had occurred in the period of bigger precipitation with 57,89 plântulas.m-2, in average, for plant-mother in the rainy station of 2004. Few seedlings had survived until the end of the period of evaluation. The stadium seedling is most critical for the survival and development of the imbu tree in caatinga. The biggest volume of precipitation significantly contributed for a bigger tax of germination and emergency of seedlings of imbu tree.