Produção e qualidade fisiológica de sementes de coentro em função de doses de nitrogênio

O objetivo dessa pesquisa foi avaliar o rendimento e a qualidade de sementes de coentro, cultivar Verdão, em função de doses de nitrogênio. Um experimento de campo foi instalado no Centro de Ciências Agrárias da Universidade Federal da Paraíba (CCA-UFPB), em Areia-PB, no período de abril a novembro de 2001, para avaliar a produção de sementes. Os tratamentos consistiram em cinco doses de nitrogênio (0, 20, 40, 60 e 80kg.ha-1) distribuídas em delineamento experimental de blocos casualizados, em quatro repetições. Após as colheitas, as sementes foram avaliadas quanto à qualidade fisiológica (germinação e índice de velocidade de germinação). O rendimento de sementes aumentou com a elevação das doses de nitrogênio, na ordem de 4,7kg.ha-1 a cada quilograma de nitrogênio adicionado ao solo, sendo o rendimento máximo de sementes (1900kg.ha-1), obtido na dose de 80kg.ha-1. A germinação máxima estimada (82%) foi obtida com a dose de 53kg.ha-1 de nitrogênio, enquanto o índice de velocidade de germinação aumentou com a elevação das doses de nitrogênio, sendo verificado um índice de 5,6 na dose máxima de nitrogênio.

The Levi-Civita space-time

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Enhanced production of parthenocarpic cucumbers pollinated with stingless bees and Africanized honey bees in greenhouses

Crops have different levels of dependence on pollinators; this holds true even for cultivars of the same species, as in the case of cucumber (Cucumis sativus). The aim of this research was to assess the attractiveness of flowers of three Japanese parthenocarpic cucumber cultivars and evaluate the importance of Africanized bees (Apis mellifera), and the Brazilian native stingless bees, Jata (Tetragonisca angustula) and Ira (Nannotrigona testaceicornis) on fruit production. Several parameters, including frequency of bee visits to flowers as well as duration of nectar collection and fruit set were examined; additionally, fruit weight, length and diameter were evaluated. Three greenhouses located in Ribeirao Preto, SP, were used for planting three cucumber cultivars (Hokushin, Yoshinari and Soudai). The female flowers were more attractive than male flowers; however, Jata bees were not observed visiting the flowers. The Africanized and the Ira bees collected only nectar, with a visitation peak between 10 and 12h. Visits to female flowers had a longer duration than visits to male flower visits in all three cultivars. Africanized bee colonies declined due to loss of bees while in the greenhouse; the native stingless bee colonies did not suffer these losses. When bees were excluded, fruit set was 78%; however, when bees had access to the flowers, fruit set was significantly (19.2%) higher. Fruit size and weight did not differ with and without bees. This demonstrates that even in parthenocarpic cucumber cultivars, which do not require pollination in order to from fruits, fruit production is significantly increased by bee pollination.