Pollination biology of Paeonia jishanensis T. Hong & W.Z. Zhao (Paeoniaceae), with special emphasis on pollen and stigma biology

The endangered wild tree peony. Paeania jishanensis T. Hong & W. Z. Zhao (f ormerly P. suffruticosa Andr. ssp. spontanea (Rehd.) S.G. Haw & L. A. Lauen er) is one of the most important ancestral stocks of cultivated tree peony, P. suffruticasa Andr. Study of the natural population at Jishan, Shanxi Pr ovince revealed that the seed set was very low (2.1 seeds per carpel). The low seed set should not be attributed to viable pollen limitation because t he plant produces a great quantity of pollen and 36-75% of pollen is TTC-te sted viable. Stigmas became receptive almost one day after the flower opene d, and receptivity lasted for several days. Ail the stigmas were suffcientl y pollinated, and pollen germinated readily on the wet crest of stigmas irr espective of whether cross pollen or self pollen was used. Hand-pollination showed that this plane was self-incompatible. No seed was harvested after self-pollination, while cross-pollination yielded 2.4 seeds per carpel. Man y pollen tubes were recorded in the stigma but extremely few in the ovary c hamber. This phenomenon indicated that the self-incompatible system was act ivated when pollen tubes reached the ovary wall. (C) 1999 The Linnean Socie ty of London.