| Autor: |
Noher de Halac, Inés, Harte, Cornelia |
| Zdroj: |
Plant Systematics & Evolution; 1977, Vol. 127 Issue 1, p23-38, 16p |
| Abstrakt: |
The homozygous Oenothera hookeri Torr. et Gray shows the typical pattern of Onagraceae with ± callose on the external walls of megaspore mother cells and tetrads. Megasporogenesis is heteropolar, and the micropylar megaspore is the mother-cell of the 4-celled embryo sac. The complex-heterozygous Oenothera biennis L. during megasporogenesis generally has callose not on the external cell walls but only on the transversal walls of the tetrad. In 95% of the ovules both the external chalazal and the micropylar megaspores develop to embryo sac mother-cells. Megasporogenesis is homopolar, and competition between two developing embryo sacs for nutrition in the ovule occurs. The embryo sac with the 'stronger' genotype wins the race against the other one. Polarity phenomena during ontogeny of the female gametophyte are related to nutritional supply and hormonal induction from the ovule. The introduction of a developmental-physiological point of view into the discussion about the evolution of the embryo sac in Onagraceae is therefore justified. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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