Pollination, pollen tube growth and fertilization in Chaenomeles japonica (Japanese quince)

Abstract

The fertilization system in Japanese quince, Chaenomeles japonica (Thunb.) Lindl. (Maloideae, Rosaceae) was studied by fluorescence microscopy. In a compatible combination, pollen grains germinated fast and pollen tubes grew rapidly, through the stylar tissue. Most of pollen tubes reached the base of the ovary within 2–6 days. In the ovary, pollen tube growth was considerably retarded, and fertilization of ovules started at the earliest 3 days after pollination. In an incompatible combination only few pollen grains germinated, and pollen tubes grew slowly and were often completely arrested in the style. The pollen tubes reached the ovary in 6–7 days. Fertilization did not take place until 7–9 days after pollination, and the percentage of fertilized ovules was very low. The same results were obtained when selfing self-incompatible genotypes. However, a small percentage of pollen tubes reached the ovary within 3–4 days in some genotypes including self-pollination (as in a compatible cross-pollination), but fertilization was not observed or considerably delayed compared to cross-pollination. C. japonica thus shows the characteristics of a gametophytic self-incompatibility system. The viable period of the embryo sac was 6–7 days in most of the investigated genotypes, and the effective period of pollination was estimated to 5–7 days. Bagging was not necessary to avoid open pollination, provided that the flowers had been emasculated previously. Emasculation or bagging did not decrease fruit set and could, therefore, be used in breeding.