Polyembryony in Oenothera
In Oenothera twin plants, two embryos in one seed, occur. They were observed in our own cultures and known to other geneticists working with this genus, like W. STUBBE and earlier RENNER (personal communication by STUBBE), but received no special attention. In the course of histological investigations on development of ovules, macrospore mother cells (MMC) and the embryo sac (ES), the female gametophyte, in Oenothera the occurrence of mature twin embryo sacs from two macrospores of one tetrad could be verified (NOHER de HALAC and HARTE 1975, SNIEZKO and HARTE 1984a, 1984b, 1986). On the other hand, ovules with two MMC were observed. Both become meiocytes and after meiosis two ES, one from each tetrad, can develop in one ovule. In the first case of twin ES, their genotypes are correlated to one another, the one being the complement of the other as far as the RENNER-complexes are concerned. In the second case of two ES in one ovule, developing from two MMC, the genotypes of the two egg cells are independent from one another. Both can have the same RENNER-complex. The question arises, how frequent a fertilisation of both egg cells in the two types of double embryo sacs in the ovules occurs and whether differences between different Oenothera-hybrids can be observed.
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