Section of Technical Crops, All-Union Institute of Plant Industry, Leningrad, USSR
1. The difference in the amount of pollen produced by the present day plant species is the result of evolution and adaptation brought about by the process of natural selection.
2. The quantity of pollen available is a very important factor in the process of sexual reproduction in plants.
3. The process of fertilization itself as also the selective advantage in fertilization change according to the amount and proportion of the fertilizing elements.
4. A “ surplus “ of pollen grains is a necessity both for ensuring the proper physiological conditions for fertilization as also for the maintenance of the mean characteristics of the variety.
5. Based on extensive and varied considerations the following conclusions are drawn: (i) pollen grains are genetically heterogenous, as with the rare exceptions there are no absolutely strictly self-pollinated plants in nature; (ii) pollination with a limited quantity of pollen does not always lead to progeny lacking in vigour; (iii) the process of sexual reproduction does not consist of the act of double fertilization only; the “ surplus “ pollen tubes penetrating into the ovary also play a very important part in the formation of the zygospore.
