Temporal and spatial variation of pollen yield in natural populations of Pinus roxburghii |
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Authors: | Vinod Prasad Khanduri |
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Institution: | Department of Forestry, Mizoram University, Tanhril, Aizawl 796001, India |
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Abstract: | Male components of the reproduction process in Pinus roxburghii were investigated for their variation in time and space as well as pollination, viz. flowering phenology, pollen production
variability and pollen dispersal, for five successive years at two different locations (at the lower and higher elevations).
The study reveals that elevation and the hour of the day are the main determinants of anthesis and microsporangium dehiscence,
because both are related to temperature and humidity. The receptivity of ovulate cone strobili or female strobili occurred
earlier at the lower elevation than at the higher elevation, with a longer receptivity period in the latter case. The phenology
of male and female cones varied significantly between years and elevations. The determinations of pollen yield considered
various sources of variability, i.e., the number of pollen strobili per branch, strobili per tree, microsporangia per tree
and pollen grains per tree. Each of these parameters revealed significant year-to-year and elevation effects. Year-to-year
variation in the production of pollen cone and pollen grains with mass production after a three-year period revealed a three-year
cycle of masting in pollen production in P. roxburghii. The pollen dispersal decreased quickly with distance from the pollen source. As a consequence, a distance of 600 m was proposed
as a minimum to prevent contamination by pollen in the management of seed orchards. The results ultimately suggest that the
ample production of pollen grains per tree along with flowering synchrony and long dispersal of pollen grains results in homogeneity
in large populations. |
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Keywords: | chir pine pollen cone gene flow elevation Himalavas |
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