Reproductive biology and breeding system of Saraca asoca (Roxb.) De Wilde: a vulnerable medicinal plant

Abstract

Ashoka (Saraca asoca) is a perennial, evergreen tree valued for its ornamental flowers and medicinal values. This species is classified as ‘vulnerable’ under IUCN list due to its dwindling population because of destructive harvesting from natural habitats. Therefore, conservation and multiplication of this species is need of the hour to utilize its astonishing medicinal uses eternally. Conservation approaches of any plant species require in-depth study of its reproductive biology, which is lacking in this species. The present study is the first detailed report on reproductive biology of S. asoca. This tree bears fragrant flowers in paniculate corymbose inflorescence from December end to May, with peak flowering during February–March. The fruits attain its maturity during last week of May–July. Seeds were dispersed from the pod to the tree premises upon complete maturity. The time of anthesis in this species is noticed in the early morning from 3.00 to 5.30 am, which coincided with anther dehiscence, stigma receptivity and insect activity. The length of the stamen and pistil points towards the pollination compatibility in both male and female parts. Pollen viability was maximum within 2 h of anthesis, which decreased thereafter and no pollens were viable after 6 h. The stigma was receptive at the time of anthesis and continued for 24 h. The tree produces bright colour attractive flowers, which changed from yellow/light orange to scarlet/red from the inception of buds to wilting. The bright color of the flowers attracted floral visitors/ pollinators thereby facilitated the pollination in this species. The observations of the floral biology and breeding system indicated the cross pollination behaviour, which limited the production of selfed seeds and would help to maintain the sustainable levels of heterozygosity among the various populations. Considerable amount of seeds produced in this species indicated that the species is capable of sustaining its progenies in the natural populations. Polyembryony to an extent of 5% was also recorded in this species.