Nitrate reductase is the first enzyme in the pathway of nitrate reduction by plants, followed by glutamine synthetase, which incorporates ammonia to glutamine. The purpose of this study was to evaluate the nitrate reductase and glutamine synthetase activity, total soluble protein content, N and Ni content in coffee leaves during fruit development under field conditions to establish new informations to help assess the N nutritional status and fertilizer management. The experimental design was in randomized complete blocks, arranged in a 3 x 6 factorial design, with five replications. The treatments consisted of 3 N rates (0 - control, 150 and 300 kg ha-1) and six evaluation periods (January, February, March, April, May, and June) in six-year-old coffee (Coffea arabica L.) plants of Catuaí Vermelho IAC 44 cv. The nitrate reductase and glutamine synthetase activities, leaf soluble protein, and N concentrations increased linearly with the N rates. During fruit development, the enzyme activity, leaf soluble protein and N content decreased, due to the leaf senescence process caused by nutrient mobilization to other organs, e.g, to the berries. Leaf Ni increased during fruit development. Beans and raisin-fruits of plants well-supplied with N had higher Ni contents. Enzyme activities, total leaf N and leaf soluble protein, evaluated during the green fruit stage in March, were significantly correlated with coffee yield. These variables can therefore be useful for an early assessment of the coffee N nutritional status as well as coffee yield and N fertilization management.

Most commercially grown cacti can be easily propagated by seed and/or cuttings. A group of rare and endangered species does not fit into this category and is therefore a good candidate for in vitro propagation productions as a tool to overcome habitat and plant-destruction. The number of rare and endangered species of Cacti goes into about 100. Many show a low production and germination of seeds and plantlets are prone to damping-off, making the in vitro propagation a feasible alternative for the multiplication and conservation of their germplasm. The aim of the present investigation is to establish a protocol for the in vitro culture and plant regeneration of Notocactus magnificus, the blue cactus, a highly ornamental species, native to Brazil. The surface sterilization of the explants was achieved with immersion for 10 min in sodium hypochlorite solution for either seeds (0

Root rot caused by the fungus Phytophthora cinnamomi is a major disease of avocados worldwide. Heat sensitivity of a collection of P. cinnamomi isolates was determined by exposing agar discs containing mycelium or mycelium plus chlamydospores at various temperatures for different periods. Long-term effectiveness of soil solarisation to control Phytophthora root rot was evaluated in two field trials. In the first, soil disinfestation by solarisation was applied in 1990 to a naturally infested plot before planting avocado (Persea americana) and viñ atigo (Persea indica) seedlings. In the second trial, established avocado trees were solarised for four consecutive summers (1996)(1997)(1998)(1999). Results for heat sensitivity showed that fungal mycelium was inactivated after 1-2 h at 38°C. However, 1-2 h at 40°C was needed to kill all propagules when chlamydospores were present. Fungal growth inhibition after thermal treatments was related to levels of time and temperature, and detrimental effects occurred as consequence of sublethal thermal doses. Soil solarisation presented long-term positive effects when applied as a preplanting treatment. Five years after solarisation, disease severity (0-5 scale where 0 = healthy and 5 = dead plant) of avocado and viñ atigo planted in solarised soil was 2.03 and 0.71, respectively, compared with 4.65 and 4.84 in controls. Eleven years after solarisation, the percentage of dead plants in solarised soil was 73% for avocado and 43% for viñ atigo but 100% in controls. In contrast, an insufficient level of control was observed in established orchards, probably because of the lower temperature reached during solarisation under the shade of tree canopy. In this situation, maximum temperatures at 5-cm depth were 10-13.7°C lower than under solar-heated mulch, only exceeding 40°C in 1997.

A protocol for large-scale Aloe vera (L.) Burm. f. production was established using micropropagation of apical buds. The effects of two chlorine-based disinfectants were evaluated on the survival of the explants in different treatments in a semisolidified Murashige and Skoog (MS) medium in the presence of 6-benzylaminopurine (6-BAP; 2 mg·L−1). During 120 days, 136 green apical shoots bearing axillary buds were multiplied four times at 30-day intervals in the same MS medium, reinoculating seven to nine explants per flask each time. The elongation and rooting processes were carried out in the same MS medium without 6-BAP. A total of 40,495 Aloe vera microplants were obtained, a yield of 300 microplants per apical bud at a rate of 1:5.3 in every multiplication period of 30 days. From that total, 38,480 Aloe vera microplants were successfully acclimatized transferring to 36- and 64-cell polyethylene trays containing proper substrate in two different ex vitro greenhouse conditions. After a 3-month period, fresh and dry matter weights of the Aloe vera plants were determined. All the data from each experimental phase were statistically analyzed. The use of 64-cell (40 cm3/cell) trays represented an economy of 47.37% in greenhouse space and 50% in the amount of substrate per Aloe vera plant.