Reproductive Phenology, Floral Biology, Pollination and Breeding System of Cochlospermum religiosum (L.) Alston in Gujarat, India

Abstract

Cochlospermum religiosum (L.) Alston is one of the most important deciduous trees in Indian subcontinent and there is limited information available on its reproductive biology and breeding system. The reproductive phenology, floral morphology, anthesis, anther dehiscence, pollen characteristics, pollen viability, stigma receptivity, pollen-ovule ratio, pollination, fertilization, fruit and seed production in C. religiosum was studied in Gujarat (India). Inflorescence emergence started in the second week of December, flower bud initiation in the third week in December and flowers opened in the second week of January. Flowering took place until the last week of February and fruiting through March with fruit dehiscence and seed dispersal in April. The flowers were large, yellow, in terminal sub-corymbose panicles. The average number of stamens produced per flower was 195.04 ± 2.19, and that of pollen grains was about 761,280, with the pollen-ovule ratio being about 804:1. The average number of ovules per ovary was 947.04 ± 6.10. The stigma receptivity was greatest in the period of maximum pollen availability: 08:00-11:00 h. Brewbaker and Kwack medium with 8% sucrose allowed the most germination in vitro (75.7%) and the longest pollen tubes were observed after 6 hours of incubation (743.8 μm). Most common floral visitors were bumble bees (Bombus sp.), which were most abundant from 09:00 to 17:00 h. In the case of natural flowers, an average of 148.16 ± 3.72 pollen grain was deposited on the stigma, of which about 46.88 pollen tube grew to the ovary, which was the fertilization success of about 31.64%. The fruit set rate was 18.88% (25 flowers per inflorescence and 4.72 ± 1.03 fruits were produced per inflorescence). Freshly collected seeds had 20-30% germination while after 1 year of storage germination dropped to 8-10%. The results generally gave the baseline data about the reproductive phenology and pollination biology of C. religiosum, which may be useful in any future studies related to its breeding, regeneration and conservation.