Fattori Modificatori Di Rapporti Numerici Tra ISESsI InCannabis Sativa L.: L'Età DelSEme

Abstract

Abstract Factors modifying the sex ratio in CANNABIS SATIVA L. — Given our lack of knowledge on the effect of age of seed and density of sowing on the sex ratio in Cannabis sativa L., over 65.000 hemp stalks were examined during the years 1959–2. These plants were sexually differentiated and were harvested from plots distributed in a randomized block. In each experiment it was found that the number of plants per square meter (which varied from 42,01 to 226,01) did not influence the sex ratio in spite of evident manifestations of natural selection due to this factor. On the contrary, alterations in the sex ratio in favour of the ♀ plants were caused by the age of the seeds, especially if plants obtanied from seeds of the same variety sown in different epochs were compared. Of course the sex ratio varies, in the same plot, according to whether all the sexually differentiated plants are taken into account or only those exceeding a given height. The evident change in the sex ratio in favour of the ♀ plants is obviously due to the death of a certain number of male embryos in the older seeds. These results do not allow a positive interpretation of the physiogenetic value of homeostasis at a sexual level, i. e. of a greater adaptation to the external conditions of the heterozygous male sex of Cannabis sativa as compared to the homozygous female sex.