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兰科中心和清华 揭秘兰花花序轴鞘片的功能及进化获国际和国内关注

兰科中心// 更新:2013-02-26 阅读 3901 次

Science Daily

http://www.sciencedaily.com/releases/2013/01/130108091347.htm

 

Orchid Adding Bird Perch for Crossing Ensures Reproduction

 

Jan 8, 2013 Chinese researchers have solved the mystery of the function of sheaths in flowering orchids. In a paper published in PLOS ONE, the team led by Zhong-Jian Liu at the Orchid Conservation & Research Center of Shenzhen and Laiqiang Huang at Tsinghua University found the perch to be essential to orchid reproduction.

 

        In many orchids such as Coelogyne rigida, the basal axis of the pendulous, multi-flowered inflorescence is covered by multiple coriaceous sheaths (bracts) forming a clavate cylindrical handle whose function has long been a puzzle and remained mysterious until today.

        A team led by Zhong-Jian Liu at the Orchid Conservation & Research Center of Shenzhen and Laiqiang Huang at Tsinghua University investigated the function of the sheaths in flowering populations of C. rigida in the limestone area of Southeast Yunnan, China, and have solved the mystery. They discovered that the sheaths-wrapped handle serves as the specialized perch (landing platform) to attract, secure and position foraging sunbird, Aethopyga gouldiae, for orderly collection and dispersal of pollinaria, attached to different spots of its beak, resulting in efficient cross-pollination and fruiting. The perch-enabled cross-pollination by sunbirds accounts for essentially all the seed production of this orchid, which was largely abolished by sheaths removal (perch damage) that reduced the visitations by sunbirds markedly both in frequency and duration, revealing an essential role of the perch in assuring the species' reproductive success by crossing.

        Intriguingly, C. rigida, while self-incompatible, has a bi-modal pollination system. It is also self-pollinated by insects, honeybee and wasp, that use the floral lip common in orchids as visiting plate, leading to infertile self-pollination which decreases (wastes) pollinaria and ovules otherwise available for fruitful cross-pollination, incurring high mating cost (gamete discounting). However, the insect-mediated fruitless self-pollination is offset by the efficient cross-pollination by sunbird.

        This represents a new and striking mode of structural adaptation that promotes cross-pollination in angiosperms. By merely adding a perch to the basal axis of inflorescence without altering the multiple flowers on it, C. rigida gains not only reproductive assurance but also mating and fertility advantages and genetic variability from crossing. It is likely that in C. rigida, self-incompatibility has evolved to avoid inbreeding depression by rendering insect self-pollination infertile, but it can't prevent self-pollination that still leads to gamete discounting at a high cost to mating, nor directly promote crossing which becomes essential for sexual reproduction; which, in turn, necessitates and selects for the evolution of an outbreeding mechanism -- the perch-enabled bird cross-pollination to assure reproductive success with multiple advantages.

 The findings may have broad implications for many other plant species with inflorescences and sheaths.

 

生物通

http://www.ebiotrade.com/newsf/2013-1/2013116122708197.htm

 

清华深圳黄来强和刘仲健:揭开兰花花序轴鞘片的功能及进化奥秘

--兰花增添鸟栖棍引导太阳鸟异花传粉保障繁殖

 

编辑推荐:黄来强和刘仲健领导的来自清华大学、深圳兰科中心及华南农大的研究团队,通过对挺茎贝母兰的深入研究,发现其花序基轴上皮质的鞘片发挥为鸟提供栖棍进行异花传粉从而保障繁殖成功的重要功能,解开了一个长久以来的科学谜团,该研究成果对认识普遍存在于许多其他植物种属的花序和鞘片的功能和进化提供了有益的启示。相关成果获同行专家高度评价,最近公布在PLOS ONE杂志上,受到国际科学传媒的关注报道。

 

在多种兰科植物例如挺茎贝母兰(Coelogyne rigida)中,下垂花序的基轴上长出许多皮质厚实的鞘片(苞片),被包裹的花序基轴呈远端增大形状,这个披护甲的棒究竟有什么功用一直是个未解之谜。

 

深圳市兰科植物保护研究中心主任刘仲健教授和清华大学深圳研究生院生物医药研究中心主任黄来强教授领导的科研团队,在中国云南东南部石灰岩地区通过对挺茎贝母兰开花居群进行深入观察和实验分析,终于解开了这一长期困扰生物学家的谜团。

 

他们研究发现,鞘片包裹花序轴构成专门的鸟栖息棍”(鸟落脚处),吸引太阳鸟(Aethopyga gouldiae)于此落脚,使鸟站稳并引导和限制其按特定动作和距离对花序的各个花朵进行觅食,使得不同花朵的花粉块粘附在太阳鸟的喙上不同的位置,太阳鸟在挺茎贝母兰的不同居群花序的鸟栖棍降落觅食,从而导致有序和高效的异花授精产生果实。该种兰花的结实全部来自太阳鸟的异花传粉,人工剥除鞘片(损伤鸟栖棍)大大降低了太阳鸟访花的频率和时间以及花的结果率,表明这一鸟栖棍承担了利用太阳鸟异花传粉产生种子从而保障繁殖成功的重任。

 

非常有趣的是,挺茎贝母兰为自交不亲和植物,却拥有双模式传粉系统:除了太阳鸟的异花传粉,它还有昆虫的自花传粉。蜜蜂和胡蜂利用兰花中常见的唇瓣作为降落平台觅食访花,导致不育的自花传粉,浪费了本可用于异花传粉的花粉和胚珠,付出高昂的交配代价。然而,太阳鸟高效的异花传粉授精,抵消减少了这种浪费,使之显得无足轻重。

 

该研究揭示了一种新颖且引人入胜的促进异花传粉的结构性适应进化模式,在被子植物中是首次报道,在兰科植物中则不同于常见的欺骗或香味的进化以适应传粉者。挺茎贝母兰仅在花序基轴上增添鞘片形成一个鸟栖棍而无需改变它多朵花的部件特性,就获得了繁殖的保障,以及自交遗传变异和交配繁育效率的提高等优势。据此推断,挺茎贝母兰原本只有昆虫自花传粉,为了防止自交衰退发展出自交不亲和机制,使自花传粉不育但不能阻止自花传粉及其配子折扣浪费的发生,这就需要有异花传粉才能进行有性繁殖,因而演化出这一鞘片鸟栖棍介导的异花传粉机制,以保障有性繁殖成功,同时在遗传和交配上克服缺点和获得优点,看来这是一种巧妙成功的进化模式。鉴于花序和类似的鞘片存在于许多兰科和其他植物种,这项研究成果对阐明同类形态结构的功能和进化具有广泛的科学意义。(生物通 2013117)

 

 

文汇报

http://whb.news365.com.cn/ewenhui/whb/html/2013-01/22/content_70.htm

 

花茎末端的棒子并非虚设

鸟类来授粉 兰花当导游

 

只有人类会做导游指引?其实植物早就会了。最近公布在PLOSONE杂志上的一篇论文显示,一种兰花——挺茎贝母兰就生有一根让鸟栖息的棒子,只要太阳鸟停在棒上,兰花就能通过限制其活动幅度,按照一定顺序游览并吃遍花朵,帮助兰花传粉。
  获得这项有趣发现的是黄来强和刘仲健领导的来自清华大学、深圳兰科中心以及华南农大的研究团队。在中国云南东南部的石灰岩地区,科学家发现了一种奇特的植物——挺茎贝母兰。开花时,它垂下一串美丽的花朵,而花茎末端却长出一根略显粗壮的、包裹着鞘片的棒子。经过长期仔细观察,科学家发现,原来这根看似无用的棒子是贝母兰用来吸引并引导它的传粉使者太阳鸟的。
  太阳鸟形如蜂鸟,色彩斑斓,啼声婉转,喜食花蜜。挺茎贝母兰就靠太阳鸟异花传粉来完成传宗接代,而这根棒子长就的形状,特别适合太阳鸟落脚,被称为鸟栖息棍。太阳鸟落脚其上后,只要想吃花蜜,就必然会在棒子上移动,而棒子的形状以及苞片位置,会让太阳鸟在棒子上移动时,恰巧可以按花序访问到每一朵花,使得不同花朵的花粉块粘附在太阳鸟的喙上不同部位。当太阳鸟在不同挺茎贝母兰之间觅食时,就帮助它们完成了授粉。
  实验证明,如果人工剥除鸟栖息棍上的鞘片,太阳鸟来访的频率和时间就会大大缩水,挺茎贝母兰的结果率也大为降低。黄来强告诉记者,挺茎贝母兰如果自花授粉,会导致不育,从而浪费了生殖资源。所以,对它而言,多长一截棒子,从而提高繁殖效率,还是划算的。(文汇报 2013122)

 

 

其他代表性媒体报道:

 

PhysOrg

http://phys.org/news/2013-01-orchid-adding-bird-perch-reproduction.html

 

eScience News

http://esciencenews.com/sources/science.daily/2013/01/08/

orchid.adding.bird.perch.crossing.ensures.reproduction

 

ResearchSEA Asia Research News

http://www.researchsea.com/html/article.php/aid/7560/cid/1/research/orchid_

adding_bird_perch_for_crossing_ensures_reproduction.html

 

Living Biology

http://livingbiology.com/orchid-adding-bird-perch-for-crossing-ensures-reproduction/

 

Orchid World

http://www.orchidworld.co.uk/news.shtml

 

First Post

http://fbsecure.firstpost.com/tag/Reproduction

 

World Data Center

http://wdc.org.ua/en/node/129374

 

SILObreaker

http://news.silobreaker.com/orchid-adding-bird-perch-for-crossing-ensures-reproduction-research-5_2266526747841265665

 

AUS-CITY Group Forums

http://www.aus-city.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=138943

 

Facebook

http://www.facebook.com/AtheistsforConservation/posts/154504761363370

 

Twitter

http://www.twylah.com/Pescalune/tweets/288687552561565696

 

VR-Zone

http://forums.vr-zone.com/science-feeds/2650942-orchid-adding-bird-perch-crossing-ensures-reproduction.html

 

World News

http://search.wn.com/?template=cheetah-search-adv/index.txt&action=search&results_type=news&search_string=inbreeding%20depression&language_id=1&sort_type=-pub-datetime&corpus=current&search_type=expression

 

搜狐

http://roll.sohu.com/20130122/n364254877.shtml

 

天津泰达

http://www.tradeteda.org/info/detail.asp?c=108567

 

天津武清

http://www.tjuda.com/a/xinwenzhongxin/xingyexinwen/shengwuyiyao/

2013/0116/36586.html

 

上海教育新闻网

http://www.shedunews.com/zixun/shanghai/zonghe/2013/01/22/481967.html

 

上海环境热线

http://www.envir.gov.cn/info/2013/1/122300.htm

 

中国青年志愿者网

http://bbs.zgzyz.cyol.com/forum.php?mod=viewthread&tid=746719

 

和讯网

http://news.hexun.com/2013-01-22/150422227.html

 

玉溪兰花网

http://www.yxlhw.com/shownews.asp?NewsID=4351

 

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