Reproductive Phenology, Pollen Production and Pollen Mediated Gene Flow in Alnus nepalensis D. Don.
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Date
2021
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College of Forestry, Ranichauri Campus, V.C.S.G. Uttarakhand University of Horticulture and Forestry
Abstract
Alnus nepalensis is a medium sized, deciduous important of tree not only occurs in the Indian sub-continent, but also in South America, Hawaii and China. It is cultivated in the hills of Himalayas around 2000 m (amsl). It is a multipurpose tree of Himalayan region growing in temperate and subtropical regions. Being non leguminous it has nitrogen fixing capacity due to the symbiotic nitrogen fixing bacteria, i.e., Frankia residing in its roots. It is prolific pioneer species in freshly exposed soil in landslide affected areas. It is used as a commercial timber production. The study of reproductive phenology, pollen production, pollen germination and pollen flow was conducted at Ranichuari, Tehri Garhwal, Uttarakhand, The observation revealed that the A. nepalensis is a monoecious tree. The male flower are composed of staminate flower called “cymules”. Importantly, it was observed that, the presence of previous year female cone, bifid stigma and protoandry condition was the unique feature of the species. Flowering in male phase was started in the last week of September and continued till November. Peak shedding of pollen generally proceeds peak receptivity by 1-2 weeks. Time between onset and peak flowering was 2 weeks 4 days and the total average duration of flowering period was about 24.8 days. Temperature played a major role in pollen release and maximum pollen was released in 300C at 13.00 hrs. Average pollen grains per tree were 2.20 × 1010. However, pollen production varied significantly among trees.
The mean pollen viability was found 100%. The maximum pollen germination of 3.69% was observed in Boric acid (25 ppm), followed by Boric acid + Sucrose 10% (2.03% in 50 ppm). The pollen ovule ratio suggests that breeding system of A. nepalensis coming under the class xenogamy. Pollen mediated gene flow study was carried out to assess the travel distance of pollen of species. It was observed that pollen of A. nepalensis can travel upto 80 m. Detailed research on reproductive phenology were conducted to determine the temporality of key events in a species' life cycle, pollen release in relation to temperature to determine the maximum pollen concentration in the atmosphere, pollen production to determine the reproductive success and health of a natural population, and long distance dispersal to eliminate population isolation. The current findings in A. nepalensis will be useful for formulating effective forest management plan and initiating various tree improvement programme.
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M.Sc. Forestry