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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (2): 60-68.doi: 10.11707/j.1001-7488.20150208

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Anatomical Characteristics of Self-Incompatibility in Camellia oleifera

Gao Chao, Yuan Deyi, Yang Ya, Wang Bifang, Liu Dongming, Zou Feng, Tan Xiaofeng   

  1. Key Laboratory of Cultivation and Protection for Non-Wood Forest Trees of Ministry of Education Key Laboratory of Non-Wood Forest Products of State Forestry Administration Central South University of Forestry and Technology Changsha 410004
  • Received:2014-04-21 Revised:2014-06-10 Online:2015-02-25 Published:2015-03-11

Abstract:

【Objective】 To investigate difference in the growth behavior of pollen tube in the pistil of Camellia oleifera after self- and out-cross pollination and to identify the types and characteristics of self-incompatibility of the plant. Further to enrich and complement the current understanding of C. oleifera in reproductive biology and also to provide a theoretical basis for increasing oil production. 【Method】 The structural characteristics of C. oleifera and the growth process of pollen tube in the pistil were observed using fluorescence microscopy combined with the modified fluorescent pallet method, fluorescence sectioning, and the routine paraffin method, according to the experimental principles of observation of the pollen tube under a fluorescence microscope as well as the characteristics of the pistil of C. oleifera. The incompatibility responses of the self-crossed pollen tube were observed using scanning electron microscopy to characterize the anatomic properties of the self-incompatibility of C. oleifera. 【Result】 The growth of the pollen tubes was observed via the stylar canal, comprised of a layer of specialized canal cells. The styles were open type and connected at the stylar base and formed a hollow placenta. After pollination, no significant difference was observed in the pollen tubes of the self-crossed and out-crossed stigma and medial styles. Pollen tubes of both styles reached the stylar base; however, a majority of the self-crossed pollen tubes grew slowly and resulted in an incompatible callose reaction as they failed to enter the locule. The magnified part of the self-pollinated pollen tubes revealed intumescence, bifurcation, coiling, folding, and wave lines that resulted from partially increased thickness of the pollen tube walls. The incompatible callose reaction was accompanied by gradual closing of the stylar canal, whereas the out-crossed pollen tubes successfully entered the locule with subsequent entry into the embryo sac at a 90° angle at the ovule micropyle position. 【Conclusion】 Based on the anatomical characteristics, we ascertained that C. oleifera was a self-incompatible plant and belonged to the prezygotic self-incompatibility type, which occurred between the stylar base and upper ovary. Future studies will be directed to understanding of the physiological and molecular mechanisms that restrict the growth of the self-crossed pollen tubes of C. oleifera. In view of the differences in fruit-setting rates among different varieties, focus will also be placed on the mechanisms behind the difference in the intensity of self-incompatibility of different varieties. Furthermore, self-incompatibility of C. oleifera occurs at the hollow stylar base where the stylar canals close intensely, which is close to the ovary, rather than in the style with a relatively loose interspace of the stylar canal. Whether this phenomenon is universal among the self-incompatible plants with hollow styles or the self-incompatible plants of the genus Camellia remains to be explored.

Key words: Camellia oleifera, self-incompatibility, pollen tube

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