Pollen storage, viability and effect of growth hormones on in vitro pollen germination in two medicinal plants (Clerodendrum colebrookianum Walp. and Clerodendrum infortunatum L.) of the tropical moist forest of North-east India

Abstract

Clerodendrum colebrookianum Walp. and Clerodendrum infortunatum L. are well known for their medicinal uses in treating various human ailments traditionally. Pollen biology study was done in both plant species to decipher pollen viability, in vitro pollen germination, and pollen storage in varied temperature conditions. Pollen viability tests was done by 2, 3, 5-triphenyl tetrazolium chloride (TTC test) for which pollen grains were collected at the anthesis stage that ascertained high viability, ranged between 71.97%±4.30 % in C. colebrookianum and 81.63%±3.23 in C. infortunatum. In vitro pollen germination was conducted under different hormones (IBA, IAA, GA3, and Kinetin) with concentrations of 100 mg L-1, 200 mg L-1 and 300 mg L-1. Highest germination percentage of 52.10±5.30% and 61.91±1.76% in GA3 (200 mg L-1) was the most suitable growth hormone concentration for inducing in vitro pollen germination in both Clerodendrum species. Statistically, the response of all the concentrations of treatments, sucrose, and hormones, with their time on in vitro pollen germination of C. colebrookianum and C. infortunatum was found significantly different (p<0.05). In contrast, non-significant differences were recorded for in vitro pollen germination between the medicinal plant species. Pollen storage under temperature gradient conditions exhibited a similar trend in the viability for both C. colebrookianum, and C. infortunatum, i.e., the pollen remained viable up to 28 days at -20°C and 6°C, respectively. This study will be helpful in future breeding, hybridization, and conservation efforts for both the Clerodendrum species.