关键词: 异型花柱植物, 青篱柴, 传粉精确性, 萌发率, 花粉管长度

Abstract

Aims: The adaptive significance of heterostyly is to improve the transfer of compatible pollen, so as to promote outcrossing. Nevertheless, many studies have found that a large number of incompatible pollens are deposited on the stigmas. At present, few studies have focused on whether the stigmas promote the compatible pollen germination and pollen tube elongation and provide evidences for the pollination accuracy hypothesis by emasculating intraflower and intraplant pollen.
Methods: Tirpitzia sinensis (Linaceae) was taken as materials, and the number of long-styled morph (L-morph) and short-styled morph (S-morph) of T. sinensis were investigated in the separate populations. The pollens and stigmas size of different morphs were measured and their surface ornamentations were observed. The viability of stigma and pollen of different flowering phases were measured. The percentage of different phenotypic pollens on the stigma were calculated. The percentage of compatible and incompatible pollens on the stigma were further calculated under intraflower, intraplant emasculation and natural control treatments. The pollen tube length and pollen germination rate of inter-morph, intra-morph and mixture pollination were measured. The heteromorphic self-incompatibility system was detected by artificial pollination treatments.
Results: There was no significant difference in the number of L-morph and S-morph of T. sinensis in the natural populations. The pollen volume of S-morph was significantly larger than that of L-morph, and the pollen surface ornamentations of the two morphs were different, but there were no significant different in the stigma surface areas and surface ornamentations of the two morphs. The pollen viability of the first flowering day was significantly higher than that of the second day, while the stigma viability had no significant difference in the first and second day of flowering. The percentage of incompatible pollen on stigma was significantly higher than that of compatible pollen in natural state. The intraflower and intraplant emasculation treatments significantly increased the percentage of compatible pollen deposition compared with the natural control in the L-morph of T. sinensis. Compared with inter-morph pollination treatment, the intra-morph pollination treatment could significantly reduce pollen germination rate and pollen tube length. Pollination treatments showed that T. sinensis was self- and intramorphic pollination incompatible.
Conclusions: These results indicate that the distyly improves pollination accuracy by promoting the compatible pollen germination and pollen tube elongation.

Key words: heterostylous plants, Tirpitzia sinensis, pollination accuracy, germination rate, pollen tube length