Aspectos da biologia reprodutiva do urucu Bixa orellana l. em Belém

Abstract

The annatto is a pre-Columbian cultivated plant that has aroused the interest of many farmers due to the importance of its natural dyes, bixin and norbixin. As part of a program to study the reproductive biology of B. orellana, the reproductive system, anther number and pollen/egg ratio were investigated in individuals located in the experimental field of EMBRAPA-CPATU, in Belém-Pa. The following controlled pollination tests were performed: 1) xenogamy with and without emasculation; 2) Geitonogamy with and without emasculation; 3) Spontaneous self-pollination; 4) Manual self-pollination and 5) Apomixis. A group of flowers were marked for control. Twenty factors were used for counting anthers (of which 10 were protected one day before emesis) and ovules, and 36 anthers for counting pollen grains. Tests on the reproductive system indicated that the species is allogamous, but self-pollination can occur. The average number of anthers was 304 +/- 71.97 and 419 +/- 16.5 in those previously protected. The average number of pollen grains per flower was 1317241.08. The pollen/ovule ratio was 23627, corroborating the allogamy indicated in controlled pollination t es t s.