Cyclic pollen production in Cedrus deodara.

Based on a seven-year study of pollen production and release in two different natural populations of Cedrus deodara from Garhwal Himalaya, India, we determined that pollen output follows a two-year cycle. Pollen productivity determinations considered various sources of variability, including the number of pollen strobili per branch, strobili per tree, microsporophylls per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and population effects. Microsporangium dehiscence took from 2.5 to 3.5 days. Maximum dehiscence was observed between 12:00 and 14:00 h, which coincides with diurnal highest temperature and lowest relative humidity. Annual production of pollen per tree varied from averages of 4.7 x 10(9), 7.2 x 10(9) and 5.1 x 10(9) in years of low production, with alternate high years, producing 12.6 x 10(9), 14.1 x 10(9), 13.3 x 10(9) and 14.0 x 10(9) pollen grains per tree. Annual pollen production in individual trees of C. deodara ranged from 1.4 x 10(9) to 22.3 x 10(9).