POLLEN GRAIN GERMINATION, STIGMATIC RECEPTIVITY AND OVULE PENETRATION IN CYTISUS MULTIFLORUS (PAPILIONOIDEAE)
In Cytisus multiflorus, a Genisteae endemic shrub in the W Iberian Peninsula, two types of morphs were detected which are differentiated by the size of the flowers and the reproductive pieces: the large-flower (LF) morph and the small-flower (SF) morph.Furthermore, the pollen grains of the LF morph are found to be less viable than those of the SF morph. A study of the stigmatic receptivity in the two morphs indicates that the stigma is receptive both in open flowers and in flower buds close to anthesis. The pollen grains are viable in both states; a result points to the existence of homogamy in this species. However, homogamy is not functional if the stigmatic surface has not been broken by pollinator visits. Hand, self-pollination experiments indicate that the pollen grains in both morphs germinate on the stigma and their pollen tubes penetrate the ovules; however, at a significantly lower percentage than in hand, cross-pollination in the case of the LF morph, but not in the SF morph. Since there is a slight overlap in flowering period between the two morphs, cross-pollination may occur not only intramorph but also intermorph. Of the four possible combinations (LF x LF, LF x SF, SF x LF, and SF x SF), the SF x SF crosses are the most effective. This may be due to the greater viability of the SF pollen grains, indicating also a lower reproductive capacity of the LF morph with respect to the SF morph.
Rodríguez-Riaño, T., López-Martínez, J., Ortega-Olivencia, A. and Deversal, J.A. (2001). POLLEN GRAIN GERMINATION, STIGMATIC RECEPTIVITY AND OVULE PENETRATION IN CYTISUS MULTIFLORUS (PAPILIONOIDEAE). Acta Hortic. 561, 95-99
pollen fertility, homogamy, stigma receptivity, pollination