fatores ambientais e genéticos na produção de sementes de acácia ...

ABSTRACT
Acacia mearnsii De Wildeman known as Black Wattle is a fast-growing species
introduced in Rio Grande do Sul State in 1918. The species is planted for wood and bark
production. Bark of this species is used for tannin extraction. Nowadays, more than
100.000 ha of black wattle is planted in Rio Grande do Sul, mainly in small rural
properties. Recently a decrease on the seed production in seed orchards and seed
production areas was observed. Therefore, the aim of this research was to study the
factors that can affect the reproductive biology of species, related to polinization (vectors
and fecundation rate) and gummosis incidence in the tree growing and flowering. The
evaluations were carried out in 2003 and 2004, in seed production areas located in three
sites in the State of Rio Grande do Sul: Piratini, Cristal and Triunfo. The methodology
used was: For the phenological evaluations, the inflorescences and pods formed, on
marked branches, were counted weekly. The pollination was evaluated through the
presence of bees and through the fecundation rate of inflorescences. For the study of
climatic effects, the temperatures and rainfalls of sites were registered. For the nutritional
evaluation, twenty leaves of each of the ten selected trees were collected. The gummosis
influence was evaluated in a progeny test through correlations between DBH, flowering
and gummosis incidence. It was concluded that: the climate conditions exerts influence in
the flowering and pods formed; the nutritional state of soil and plants affects the pods
formed, being that the place with better flowering and pod formed is which presents soil
more fertile; the pollinators is not the cause of less seed production; and the presence of
gummosis had no significant correlation with flowering.
Key-words: black-wattle, environment factors and seed production.
xi