Strobilus

Abstract: The female and male flowering frequency were studied in a clone trial of Picea abies at Roskar nine kilometers north-east of Stockholm During 1971 the extension in time of pollen shedding and female receptivity was recorded following daily examination of individual strobili The data obtained revealed a great variation in female as well as male flowering between the clones Only a part of this variation could be attributed to differences in height of the clones Great yearly variations in flowering of individual grafts were noticed Based on the flowering frequency as well as the pollen shedding and female receptivity during each day, the expected contribution of the different clones to the offspring was calculated According to the calculations four of the clones contributed 55 per cent of the genes to the offspring Many (66) of the 190 theoretically possible combinations among the 20 clones occurred in a lower frequency than 01 per cent The consequences of the data obtained for the genetic composition of the seed orchard progeny were discussed

Abstract: The growth behavior of grafted scions from 1-, 4-, 8- and 12-year-old ortets representing five half-sib loblolly pine families was observed over a two-year period (three for strobilus production) following grafting. Significant, persistent decreases in total number of cycles produced, height and diameter increment, number of branches produced, foliar surface area and total scion biomass were observed with increasing age. Needle length, diameter, and ability to form male and female strobili increased with increasing scion age. The persistence of these differences is not a function of size since the scions were the same length at grafting. The significance of these results to the establishment of breeding orchards, early genetic evaluation, and the nature of phase change is discussed.

Abstract: Canada yew (Taxus canadensis) populations currently browsed by white-tailed deer (Odocoileus virginianus) or browsed by deer in the past had significantly lower production of male strobili, female strobili, and seeds than unbrowsed yew populations. Exclosure studies showed that protected yews produced significantly more male and female strobili than unprotected yews, but only after several years of protection. Seed production did not respond as readily to protection from deer perhaps because of reduced pollination levels in browsed yew populations. Previously unbrowsed yews were clipped at different levels of removal of available browse (control (no removal), 25%, 50%, 75%, and 100% removal) to simulate deer browsing. Reduction in male strobilus production was linearly related to clipping intensity in three years of observation. Female strobilus production was significantly reduced only at the 100% level of removal. Intermediate levels of clipping may have even stimulated production of female strobili. Analysis of covariance, with previous year's branch production as the covariate, showed no significant effect of clipping on male strobilus production except in the 100% removal group. Female strobilus production showed no such covariance with branch production. Effects of clipping on seed production could not be reliably assessed in 1984 and 1985 due to low seed production. Seed production in 1986 was significantly reduced only in the 100% removal group. Field observations of deer browsing of Canada yew indicate that 100% levels of removal are typical of natural levels of browsing.