Sporogenesis and gametophyte development in Chaenomeles japonica (Japanese quince)

Abstract

Micro- and macrosporogenesis as well as the male and female gametophyte development were studied in Chaenomeles japonica (Japanese quince). The archesporium of the microsporogenesis was already recognised in November. The development was arrested during winter and was not resumed until March the following spring. The process followed the normal route and resulted in binucleate pollen. One deviating genotype instead produced 10–12% trinucleate pollen. The pollen grains were ripe and ready for dispersal 2–3 days before anthesis. The second mitotic division took place in the pollen tube. In general, the percentage of fully developed pollen grains was over 70%. One presumed C.× superba genotype turned out to be completely male sterile. The development of the male sterile and the male fertile genotypes diverged at the tetrad stage. In the male sterile genotype, the microspores did not develop a complete exine. The tapetum still persisted after the tetrad stage, then vacuoles developed, which resulted in a complete compression of the microspores. The development of the female gametophyte started in the middle or in the second half of April, 3–4 weeks before anthesis. Most of the genotypes examined followed a normal route corresponding to the Polygonum type. A ripe, octanucleate embryo sac developed 2–4 days after anthesis, depending on genotype and year. Almost all genotypes produced some flowers with abnormal embryo sacs.