Sexual asymmetry in Scots pine seed orchards

In seed orchards of Scots pine Pinus sylvestris L., the reproductive process is affected by the variation among the clones in fertility and abundance of male and female flowering. There were significant differences between the clones in relative proportion of male and female strobili as well as in seed yield. Thus, clones in Scots pine seed orchards may differentiate into "seed" and "pollen" clones. The least fertile clone produce 4.6 times less pollen than the most fertile clone, while cone yield of the least yielding clones was 5.5 times smaller than that of the most yielding clones. Amount of the pollen dispersed at the upper part of the crowns was two times greater than at the base of the crowns. The minimum amount of pollen needed for successful fertilization of an ovule was 1500 grains per cm2. There was no significant relationship between sexual asymmetry of the parental clones and height growth of their progeny.