Polytenization in the antipodal nuclei of wheat [Triticum aestivum L.], triticale [xTriticosecale Wittm.] and their reciprocal crosses

The antipodals of the mature embryo sacs of wheat (Triticum aestivum L.) and triticale (xTriticosecale Wittm.), as well as those of the embryo sacs developing after reciprocal cross pollination of these taxa were investigated. In a single embryo sac there were on average 14 antipodals in triticale and 18,5 in wheat. The endoreduplication cycles were stated in the antipodal nuclei. Before the pollination they led to a maximum degree of ploidy 8n in triticale and 16n in wheat. Within three days after the pollination a number of the antipodal nuclei reached 256n in the triticale ♀ x wheat ♂ cross and 512n in the reciprocal cross. The polytene chromosomes resulted from a gradual condensation of chromatin with the increasing degree of ploidy. They were the only type of the chromatin organization found in all the antipodal nuclei over 32n degree of ploidy. In both crosses the first signs of disintegration of the antipodal apparatus were found three days after the pollination. At that time the cellularization of the initially coenocitic endosperm was starting in the triticale ♀ x wheat ♂ cross. By contrast, the latter process was withheld in the reciprocal cross, which together with other disturbances of the endosperm development caused almost complete kernels sterility. The possibility of improper interaction of the mother derived antipodal apparatus with the hybrid endosperm was discussed.