Reproductive biology of the Hamelia pattens Jacq. (Rubiaceae) in northern India

Abstract

A study of floral biology and the breeding system of Hamelia patens Jacq. (Rubiaceae) was carried out in northern India from March, 2005 to February, 2007. The data obtained was compared with those obtained from the original area of distribution of the species. This species is an ornamental shrub cultivated in the gardens for its beautiful orange-red bunches of flowers and copper green leaves. The tubular flowers are yellowish orange or orange-red, 3.05±0.12 cm long and last for three days. They are protrandous and the pollen is available 12-14 h before the stigma becomes receptive. The beginning of anthesis takes place between 0230-0300 h and the opening of the bifid stigma occur in the afternoon between 1430-1700 h. The nectar is secreted during both the male and female phases, with higher concentrations of sucrose. The floral biology is related to environmental factors, particularly temperature. The quantity of nectar and pollen fertility declines with the rise in temperature and in summers when temperature ranges between 37° C to 45° C, nectar was more or less absent and only 2-3% pollen were fertile. The flower visitors included honeybees, butterflies, wasps, house flies, ants and sunbirds. Ants and house flies are robbers whereas; all the others act as pollinators. Squirrels were frequently seen, but they just eat away the base of the flower full of nectar. The plant is selfcompatible and facultative xenogamous. The natural fruit-set is only 7% but seed-set rate is slightly higher. Thus, this species growing in its natural habitat in Argentina and in its cultivated form in India exhibits some differences in pollen fertility, stigma receptivity, nectar quantity and quality and behaviour of flower visitors and absence of hummingbirds from India. These are responsible for the difference in the reproductive success of this species at two places. It seems that this species is under the process of acclimatization in North India.