Page 38 - 《广西植物》2023年第5期
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8 1 8                                  广  西  植  物                                         43 卷
                   Style lateral bending and its pollination adaptation

                                   in Gyrocheilos (Gesneriaceae)


                                              1ꎬ2                1ꎬ2                1ꎬ2ꎬ∗
                                SUN Haoran ꎬ LING Shaojun ꎬ REN Mingxun
             ( 1. Ministry of Education Key Laboratory for Genetics and Germplasm Innovation of Tropical Special Forest Trees and Ornamental Plantsꎬ Hainan
              Universityꎬ Haikou 570228ꎬ Chinaꎻ 2. Center for Terrestrial Biodiversity of the South China Seaꎬ Hainan Universityꎬ Haikou 570228ꎬ China )

                 Abstract: Gyrocheilos is a small genus of Gesneriaceae endemic to hight altitude mountains in Southwest China and
                 Guangdong Provinceꎬ with only five species. This genus is characterized by laterally bending styleꎬ which curves 90° at
                 the top of the style and the stigma right at the mouth of floral tube. This unusual floral trait may have special evolutionary
                 and adaptive mechanisms. In this paperꎬ three Gyrocheilos speciesꎬ i.e. G. chorisepalusꎬ G. retrotrichusꎬ G. microtrichus
                 were examined to figure out the developmental patterns of floral lateral bending. Breeding systemsꎬ floral syndrome and
                 pollination processes were also studied in G. retrotrichus at Dawuling Mountainꎬ Guangdong Provinceꎬ to explore its
                 pollination adaptations. The results were as follows: (1) G. microtrichus had only left ̄bending styleꎬ while right ̄bending
                 style were observed in several flowers (2%-3% of the total flowers) of G. chorisepalus and G. retrotrichusꎬ although the
                 individuals and populations were dominated by left ̄bending style. (2) Pollination observation found that style lateral
                 bending occurred at the early stage of floral bud in G. retrotrichusꎬ with two fertile stamens were anther ̄united and
                 hidden at the middle of the floral throatꎬ and there was no left and right mirror symmetry relationship with the lateral
                 style. (3) The pollen ̄ovule ratio (P / O) was ( 456.98± 15.55)ꎬ belonging to facultative outcross breeding system.
                 G. retrotrichus had a certain pollen limitation and self ̄pollinationꎬ but the germination rate of outcross seeds was higherꎬ
                 and there might be inbreeding decline. ( 4) There were few floral visitors and the frequency was low of G.

                 retrotrichus. The main floral visitors were Halictidaeꎬ Bombus and Syrphidae. Bombus were largeꎬ and they landed on the
                 bent style and the lower lip of the petals when visiting flowers. The side and lower part of the chest could effectively
                 contact the stigma. (5) The detected reflected lights of flowers were composed of purple and blue ̄purple lights and the
                 lower lips and outer floral tube with the highest reflection intensityꎬ more likely to attract bees to land on the corollas
                 lower lip. Molecular phylogeny indicated that the closest genus of Gyrocheilos was Didymorcarpusꎬ which was
                 characterized by style downward bending and mirror ̄image flowersꎬ suggesting the style lateral bending in Gyrocheilos
                 probably evolved from either of these conditions. In conclusionꎬ the lateral bending style might provide landing platform
                 for pollinators and the stigma above the lower lips increase contact probability the floral visitorsꎬ which is an adaptation
                 to the very low insect visitation due to fragmented and foggy habitats in high altitude areas.
                 Key words: floral syndromeꎬ mirror ̄image flowersꎬ pollination mechanismꎬ breeding systemsꎬ Gesneraiceae



                被子植物花柱的形态与空间位置是决定柱头                            al.ꎬ 2006ꎻ Ren et al.ꎬ 2013) 等ꎬ成为研究花部综
            落置花粉、胚珠授粉成功的一个关键因素ꎬ往往是                             合征(floral syndrome)、花-传粉者协同进化的关键
            由访问最频繁、最有效的传粉者塑造的( Mayfield                        性状之一(黄双全ꎬ2007)ꎮ
            et al.ꎬ 2001ꎻ Fenster et al.ꎬ 2004)ꎮ 在适应不同传            苦 苣 苔 科 ( Gesneriaceae ) 圆 唇 苣 苔 属
            粉者类型与访花行为以最大化柱头接受同种花粉                              (Gyrocheilos)的花柱形态非常特别:花柱不仅偏转
            概率的 选 择 压 力 下ꎬ 花 柱 出 现 了 极 大 的 多 态 性               在花冠筒的一侧ꎬ而且花柱顶端呈 90°弯折ꎬ使得
            (Barrett et al.ꎬ 2000 )ꎬ 如 花 柱 运 动 ( Li et al.ꎬ    花柱顶端 2 ~ 3 mm 的部分横在花冠筒开口、柱头
            2001ꎻ Yu & Huangꎬ 2004ꎻ 段 友 爱 和 李 庆 军ꎬ             处于花开口处的中央位置( 韦毅刚ꎬ2010)ꎮ 这种
            2008)、柱 头 裂 片 开 合 ( Fetscherꎬ 2001ꎻ Yang et        花柱侧偏弯折现象不同于目前已知的花柱类型ꎬ
            al.ꎬ 2004)、异长花柱( Barrett et al.ꎬ 2000)、镜像          可能存在不一样的发育过程和传粉适应机制ꎬ对
            花的侧偏花柱(Jesson & Barrettꎬ 2002aꎬ bꎻ Gao et          认识苦苣苔科传粉系统演化和物种形成机制具有
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