Biodiversity Science ›› 2012, Vol. 20 ›› Issue (3): 337-347.doi: 10.3724/SP.J.1003.2012.11243

Special Issue: Polination Biology: Theory and Primary Practice

• Original Papers • Previous Article     Next Article

Distyly and heteromorphic self-incompatibility of Hedyotis pulcherrima (Rubiaceae)

Xinxin Liu1, 2, Xiaoqin Wu1*, Dianxiang Zhang1   

  1. 1Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650

    2Graduate University of the Chinese Academy of Sciences, Beijing 100049
  • Received:2011-12-29 Revised:2012-03-30 Online:2012-05-09
  • Xiaoqin Wu E-mail:wxq@scib.ac.cn

Heterostyly is a genetically controlled floral polymorphism, which includes both distyly and tristyly. We investigated morph ratio, floral and pollen morphology, and self-incompatibility of Hedyotis pulcherrima. Overall, the natural population of H. pulcherrima was isoplethic, containing long-styled and short-styled morphs with an equilibrium 1:1 ratio. Long-styled and short-styled morph exhibited a precise reciprocal herkogamy, which was significantly correlated with corolla length. Stigma-lobe length, pollen size, and starch content in pollen grains were dimorphic in the two morphs of H. pulcherrima, whereas pollen germination and pollen tube growth in vitro were not significantly different between the two morphs. Artificial pollination revealed that pollen tube shape was normal in both morphs where pollen tubes reached the ovary 24 h after pollination. However, pollen tube growth was arrested in the stigma with the accumulation of callose in the swollen tips in two morphs with self and intramorph pollination, indicating strict heteromorphic self-incompatibility in H. pulcherrima. No fruit was produced in emasculated netted flowers, suggesting the absence of apomixis. Artificial intermorph pollination resulted in 100% of fruit set, significantly higher than those with open pollination. Our results indicate that H. pulcherrima is a typically distylous species with heteromorphic self-incompatibility.

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