早春不稳定传粉环境中新疆郁金香混合交配系统中的自交策略

【目的】在植物的所有生活史特征中,交配格局可能是对宏观进化影响最大的因素。在不确定的传粉环境中,两性花植物常常具有潜在的自交能力,鉴于自交的交配代价,两种交配方式如何权衡,一直是深入理解交配系统演化的关键问题。【方法】为了探讨早春不稳定传粉环境中植物的自交策略,以早春短命植物新疆郁金香为研究对象,通过野外观测及人工控制实验对自然居群的开花习性、传粉者类群、散粉动态、自花粉传递模式和交配系统等进行研究。【结果】（1）新疆郁金香自然种群4月上旬或中旬开花,单花期5-6 d,白天开放晚上闭合,花粉的释放从外轮开始,由下到上呈拉链式次序呈现。（2）传粉者主要为蜂类和食蚜蝇,访花频率普遍较低,且在年份间存在较大差异,但结实率普遍较高。（3）控制授粉实验表明居群为异交为主,部分自交亲和的混合性交配系统类型。傍晚花闭合时雄蕊的自主运动促进了柱头的自花授粉,这一传粉模式促进了竞自交的发生,但大量自花粉的落置发生在开花后的第4 d,占自花粉总落置量的50.22%,为一种延迟自交的机制。【结论】在传粉受限的情况下,新疆郁金香的竞自交和延迟自交促进了柱头的花粉落置,这种集异交、竞自交和延迟自交为一体的交配策略灵活地应对了早春不稳定的传粉环境,是对早春低温度条件下不确定传粉服务的一种适应,也是早春短命植物的一种繁殖保证对策。     

浅裂剪秋萝和丝瓣剪秋萝传粉特性的初步研究

为了探究浅裂剪秋萝(Lychnis cognata)和丝瓣剪秋萝(L. wilfordii)的传粉生物学特征, 从花部特征、花粉呈现规律及传粉者访花行为等方面对其开展研究。结果表明, 2种剪秋萝的花期持续时间相近, 但浅裂剪秋萝始花日期较早; 二者花部特征虽有显著差异, 但主要传粉者均为碧翠凤蝶(Papilio bianor)。在开花过程中, 2种剪秋萝的雄蕊均分2批呈现花粉, 第1批雄蕊的花粉生活力在开花后第1天达到最大值, 而第2批雄蕊在第2天达到最大值。浅裂剪秋萝的柱头可授性在开花后第5天最强, 而丝瓣剪秋萝在开花后第4天最强, 花粉生活力和柱头活性的时间差异表明两物种均为雌雄异熟。两物种共同的传粉者碧翠凤蝶对浅裂剪秋萝的访花高峰出现在上午8:00-11:00, 而对丝瓣剪秋萝的访花高峰出现在上午11:00-12:00, 导致访花高峰出现差异的主要影响因素可能是生境和花药开裂时间。     

雄全异株植物瘿椒树(省沽油科)的传粉生物学

从开花动态、传粉昆虫、花的形态结构、繁育系统、花粉活力和柱头可授性等方面研究了我国特有珍稀植物瘿椒树(Tapiscia sinensis Oliv.)的传粉生物学特性。瘿椒树是典型的雄全异株植物,两性花中含有功能性花粉,且自交亲和,但雄花花粉活力和萌发力是两性花的10倍以上。雄株和两性植株具有相同开花物候期,花期均为5月下旬至6月上旬,单花期为4-5天,雄花和两性花的5枚花药开裂的不同步性明显延长了散粉时间。两性花雌蕊先熟,柱头可授性较长。具有适应风媒和虫媒传粉的花部特征。传粉昆虫主要为蜜蜂科(Apidae)和食蚜蝇科(Syrphidae)昆虫,访花高峰期为8:30-10:30。维持瘿椒树雄全异株的可能机制是:雄株总体上增加了异交花粉的数量和质量;两性花的雄蕊为该物种提供了繁殖保障,同时为传粉者提供了报酬。     

侧穗凤仙花的传粉生态和繁育系统

通过对峨眉山特有种侧穗凤仙花的开花生物学特性、花器官结构、传粉者种类和访花行为、繁育系统、花粉胚珠比(P/O)及花粉活力的研究.发现居群之间花的寿命变化比较大,它们的雄蕊期长,雌/雄蕊期比为0.12～0.17;花粉胚珠比达到4.6万,花粉在开花第一天有很高的活力(＞90%);传粉者为熊蜂和天蛾,熊蜂包括贞洁熊蜂、白背熊...     

动物传粉植物花粉呈现时序的进化意义

由动物传粉的植物为了使供体花粉能够被高效地传递到受体柱头上, 进化出了多种多样的花部特征, 花粉呈现时序便是其中之一。植物主要通过包装机制和分摊机制控制花粉呈现的速度以限制昆虫一次拜访转移的花粉量。花粉呈现理论(PPT)认为: 花粉逐步呈现策略倾向于出现在传粉者数量丰富但传粉效率低的植物中, 而花粉同时呈现策略则多出现在传粉者少但传粉效率高的植物中。本文对花粉呈现时序的相关研究进行了总结, 重点介绍: (1) 限制花粉转移的花部机制; (2)花粉呈现理论; (3)花粉呈现时序的适应意义。目前的研究主要集中在花粉呈现时序对传粉动物的适应性上, 但环境因子对花粉呈现时序也有一定的影响。PPT数学模型还不能完全预测特定环境中植物的花粉呈现时序。因此, 有必要选择合适的植物类群, 从花部综合特征、传粉系统、交配系统和环境等方面进行综合研究, 进一步揭示动物传粉植物花粉呈现时序的适应意义。     

稀有植物小丛红景天花部综合特征与繁育系统

对稀有物种生物学特征及繁育系统的研究将有利于我们对稀有物种的保育。该文通过野外定位观测稀有植物小丛红景天(Rhodiola dumulosa)的花部综合特征,并运用杂交指数、花粉-胚珠比的方法首次对其繁育系统进行初步测定。结果表明:该物种单花花期一般为5~6 d,开花过程中花柱逐渐伸长并向外弯曲,子房开裂并逐渐伸长,花药散粉具有先后顺序,一般外轮对萼花药先散粉,其后1 d左右对瓣花药开始散粉。单花花期依照其形态和散粉时间可分为6个阶段:花蕾期、内轮散粉期、内轮散粉末期、外轮散粉期、外轮散粉末期和凋谢期。而种群花期一般可持续30 d以上,不同海拔观测地点有所不同,海拔2 202 m处的观测地点B开花物候最为滞后。由于其杂交指数不小于4,花粉-胚珠比在700~1 000之间, 根据Dafni(1992)和Cruden(1977)的标准,初步判定该物种的繁育系统属于异交为主,部分自交亲和,传粉过程需要传粉者。     

雄全异株植物瘿椒树（省沽油科）的传粉生物学

从开花动态、传粉昆虫、花的形态结构、繁育系统、花粉活力和柱头可授性等方面研究了我国特有珍稀植物瘿椒树（Tapiscia sinensis Oliv.）的传粉生物学特性。瘿椒树是典型的雄全异株植物,两性花中含有功能性花粉,且自交亲和,但雄花花粉活力和萌发力是两性花的10倍以上。雄株和两性植株具有相同开花物候期,花期均为5月下旬至6月上旬,单花期为4-5天,雄花和两性花的5枚花药开裂的不同步性明显延长了散粉时间。两性花雌蕊先熟,柱头可授性较长。具有适应风媒和虫媒传粉的花部特征。传粉昆虫主要为蜜蜂科（Apidae）和食蚜蝇科（Syrphidae）昆虫,访花高峰期为8：30-10：30。维持瘿椒树雄全异株的可能机制是：雄株总体上增加了异交花粉的数量和质量;两性花的雄蕊为该物种提供了繁殖保障,同时为传粉者提供了报酬。     

植物的生殖讲座（四）：花药的发育和雄配子体的形成

植物的生殖讲座（四）──花药的发育和雄配子体的形成王景林（首都师范大学生物学系１０００３７）被子植物开花时,花粉从花药中散出进行传粉和受精。花药是产生花粉的地方,我们若要了解小抱子的形成和雄配子体的发育,就要从花药的发育谈起。花药是一朵花雄蕊的主要组...     

两性花的雄蕊运动:多样性和适应意义

雄蕊运动指雄蕊在自身能量支持下发生的主动运动,不包括雄蕊在访花者触碰下造成的被动位移。该文总结了雄蕊的应激运动、快速猛烈弹射、缓慢运动以及级联运动等4种主要类型,分析了这些运动类型的系统分布及繁殖适应意义等方面的研究进展。雄蕊的应激运动由访花者或其他外力诱发,可能起到促进散粉和实现繁殖保障的作用;雄蕊快速猛烈的弹射运动可将花粉猛然撒向空中或访花者身上,促进了花粉的风媒或虫媒散布;缓慢运动的雄蕊可能通过在不同花期改变雄蕊的空间位置和雌雄异位程度来调节繁殖策略,或主动将雄蕊花药移至特定部位(如柱头表面)实现自交;雄蕊逐一、依次发生的级联运动较为复杂,主要分布在刺莲花科、梅花草科、旱金莲科和芸香科中,目前还缺乏实验研究;但根据"花粉呈现理论"以及其他类型的雄蕊运动研究结果,雄蕊的级联运动可以将花粉分批呈现给不同的传粉者,通过不同传粉者的分别传粉来提高花粉的输出;而且可避免已散粉雄蕊对即将散粉雄蕊的干扰,同时可能也降低了雌雄功能干扰和(或)花内自交。在芸香(Ruta graveolens)中,级联运动之后的雄蕊还会在花末期再同时向花中央运动;这种多向、多次运动方式是目前发现的最复杂的雄蕊运动类型。雄蕊运动领域值得今后开展进一步实验研究的方向主要有:1)雄蕊运动尤其是级联运动对雌雄功能干扰(性别间干扰)、雄蕊与雄蕊的"性别内干扰"等植物繁殖格局的影响;2)雄蕊运动与雌雄异熟、雌雄异位等花部特征的相互作用;3)雄蕊运动复杂类型的生理与发育机制。     

被子植物退化雄蕊的功能类型及其意义

退化雄蕊是指没有花药或花药不可育的雄蕊,发现于被子植物32.5%的科以及54.4%的属中,它们在形态和生化组成上都与可育雄蕊有着显著区别。虽然丢失了产生可育花粉的能力、无法发挥雄性繁殖功能,某些退化雄蕊在进化过程中重新获得了一些有助于植物繁殖成功的新功能。本文将这些具有功能的退化雄蕊细分为8类:(1)信号型;(2)报酬型;(3)欺骗传粉型;(4)辅助传粉昆虫在花内活动;(5)辅助授粉;(6)协助花粉二次呈现;(7)保护其他花结构;(8)避免自交。退化雄蕊作为花结构的一部分,其功能集中于促进植物的繁殖成功,主要通过与传粉昆虫的相互作用来提高传粉效率。此外,某些植物的退化雄蕊也可能同时具有多种功能,并且其功能的强弱与传粉者的种类、行为、大小和频率相关。正确评估退化雄蕊对植物繁殖成功的影响,需要多学科手段来系统的研究,以便能更加深入的理解不同近缘关系的物种间退化雄蕊功能的差异,揭示退化雄蕊在被子植物系统进化中的意义。     

地下结实植物白番红花的繁育系统与传粉生物学

地下结实是植物用来防御不利环境的一种策略, 研究地下结实植物的繁殖特性, 可以揭示它们的繁殖对策多样性, 对于探讨环境选择压力对其繁育系统及后代适合度的影响具有重要意义。白番红花(Crocus alatavicus)是一种分布在天山西部亚高山带、具地下芽和地下结实特性的早春短命植物。我们采用野外观测和统计分析方法, 对该物种的繁育系统与传粉生物学及其对亚高山环境的适应进行了研究。研究结果表明: 白番红花具有先花后叶的特性, 于4月上中旬始花, 呈爆发式开花式样; 花白色, 无花蜜无气味; 开花时, 下位子房位于地下, 花蕾在地上开放并随光照变化而开闭; 单花花期为6–9 d, 花萎蔫时花粉活性仍保持在75.39±5.69%, 柱头可授期为8 d。人工授粉实验结果显示, 该物种属于兼性异交繁育系统, 且具有自主自花授粉能力。白番红花属于泛化传粉系统, 鲁熊蜂 (Bombus lucorum)、老条蜂 (Anthophora senilis)和黄腹地花蜂 (Andrena capillosa)是有效传粉昆虫, 通过采食花粉进行传粉, 访花频率分别为0.50±0.27次•花–1•h–1、0.18±0.08次•花–1•h–1和0.13±0.05次•花–1•h–1。在天山西部亚高山早春环境中, 白番红花不仅利用其开花式样、泛化传粉系统及早春空白生态位来提高传粉效率, 而且通过自交亲和及主动自花授粉等繁育系统特征来弥补传粉昆虫少及访花频率低的不足, 从而保障繁殖成功。     

异型花柱植物喀什补血草的传粉者功能群与花粉转移效率

异型花柱是受遗传控制的花柱多态现象, 被达尔文认为是植物通过在传粉者体表不同部位滞落花粉以促进型间花粉准确传递的一种适应。该现象虽已受到广泛关注, 但在一些花型变异较大且不稳定的传粉系统中, 不同传粉者对各花型繁殖所产生的影响仍知之甚少。该研究以分布于新疆天山南坡的一个有同长花柱共存的异型花柱植物喀什补血草(Limonium kaschgaricum)种群为研究对象, 对其花型构成及频率、传粉者及花粉转移效率等进行了调查分析。结果表明: 1)种群中除了存在雌/雄蕊长度交互对应的长(L)/短(S)花柱型花外, 还有雌/雄蕊同长的花(H型), 且各花型花的花冠口直径、花冠筒长及花粉量等参数间无差异, 但花粉纹饰和柱头乳突细胞形态具二型性。其中, H型花的花粉和柱头形态与L型花(或S型花)的一致。2)花型内和自花授粉均不亲和; 型间授粉时, 花粉和柱头形态不同的花型间亲和, 反之不亲和。3)种群内存在长/短吻两类传粉昆虫。在以短吻传粉者为主的盛花初、中期, L和H型花柱头上的异型花粉数均显著高于S型花的, 且L和S型花高位性器官间的异型花粉传递效率高于低位性器官间的; 而在以长吻传粉者为主的盛花后期, L和S型花的柱头间异型花粉数无显著差异, 且高/低位性器官间具有相同的异型花粉转移效率; 与传粉者出现时期相对应的、在花期不同阶段开放花的结实率也明显不同。4)长/短吻昆虫具明显不同的传粉功能, 短吻昆虫只能对L和H型花进行有效传粉, 且访花频率和型间花粉转移效率较低, 为低效传粉者; 而长吻昆虫对各花型均能有效传粉, 具高的访花频率和型间花粉转移效率, 为高效传粉者。因为长吻昆虫的阶段性出现所形成的不稳定传粉系统, 使低效的短吻昆虫可能会成为种群中花型变异的驱动力, 并使S型花受到更大的选择压力。H型花克服了柱头缩入的弊端, 可能会成为不稳定传粉系统下的一个替代花型而持续存在。     

宁夏枸杞的花粉呈现式样及交配系统研究北大核心CSCD

被子植物的花回馈、雌雄蕊时空分离特征和花粉呈现式样等花部特征及传粉者效率会影响雄性适合度和有性繁殖过程。宁夏枸杞(Lycium barbarum)是中国宁夏、新疆、内蒙等干旱和半干旱地区分布的特有种。该研究对新疆喀什地区宁夏枸杞自然种群的花部综合征、花粉呈现式样、花回馈、传粉者行为与交配方式的关系进行观察及统计分析,以探讨其花粉逐步呈现的适应性及其在提高雌雄繁殖过程中的意义。结果表明:(1)宁夏枸杞的单花寿命为(4.07±0.15) d,而雄性持续时间(0.07±0.01 d)比雌性持续时间短(4±0.01 d);花寿命内雌蕊长度比雄蕊长,属柱头探出式异位类型;花粉呈现式样为不完全逐步呈现。(2)花寿命不同阶段花回馈间存在显著差异。(3)意大利蜜蜂(Apis mellifera)、熊蜂(Bombus sp.)、食蚜蝇(Syrphidae sp.)是宁夏枸杞在自然居群的主要访花者,其中熊蜂和食蚜蝇是主要传粉者,但传粉者效率低,属于高移出低沉积类型。(4)宁夏枸杞的花粉胚珠比(2 448.11±448.32)及授粉实验结果均表现出兼性异交特征;自发自交及人工自花授粉花的座果率及结籽率很低,属于自交不亲和类型;自然传粉花的座果率及结籽率比人工去雄异花低,存在其较高的花粉限制(40.71%)。研究发现,宁夏枸杞花部综合征表现出雌雄异位和花粉不完全逐步呈现式样,这是避免雌雄功能及雄蕊各花药间的干扰、减少花粉同步移出及保障其雄性适合度的有效途径,但自然居群的传粉者种类限制、传粉效率低以及自交不亲性是导致宁夏枸杞花粉限制及降低雌性繁殖成功的主要原因。     

The reproductive assurance benefit of selfing: importance of flower size and population size

Autonomous selfing can provide reproductive assurance (RA) for flowering plants that are unattractive to pollinators or in environments that are pollen limited. Pollen limitation may result from the breakdown of once-continuous habitat into smaller, more isolated patches (habitat fragmentation) if fragmentation negatively impacts pollinator populations. Here we quantify the levels of pollen limitation and RA among large and small populations of Collinsia parviflora, a wildflower with inter-population variation in flower size. We found that none of the populations were pollen limited, as pollen-supplemented and intact flowers did not differ in seed production. There was a significant effect of flower size on RA; intact flowers (can self) produced significantly more seeds than emasculated flowers (require pollen delivery) in small-flowered plants but not large-flowered plants. Population size nested within flower size did not significantly affect RA, but there was a large difference between our two replicate populations for large-flowered, small populations and small-flowered, large populations that appears related to a more variable pollination environment under these conditions. In fact, levels of RA were strongly negatively correlated with rates of pollinator visitation, whereby infrequent visitation by pollinators yielded high levels of RA via autonomous selfing, but there was no benefit of autonomous selfing when visitation rates were high. These results suggest that autonomous selfing may be adaptive in fragmented habitats or other ecological circumstances that affect pollinator visitation rates.     

Changes in Florets’ Vertical Direction within Inflorescence Affects Pollinator Behavior,and Fitness in <i>Trifolium repens</i>

Ecological interactions between flowers and pollinators greatly affect the reproductive success. To facilitate these interactions, many flowers are known to display their attractive qualities, such as scent emission, flower rewards and floral vertical direction, in a rhythmic fashion. However, less is known about how plants regulate the relationship between these flower traits to adapt to pollinator visiting behavior and increase reproduction success. Here we investigated the adaptive significance of the flower bending from erect to downward in Trifolium repens. We observed the flowering dynamic characteristics (changes of vertical direction of florets, flowering number, pollen grain numbers, pollen viability and stigma receptivity over time after blossom) and the factors affecting the rate of flower bending in T. repens. Then we altered the vertical direction of florets in inflorescence of different types (upright and downward), and compared the pollinator behaviors and female reproductive success. Our results showed that florets opened sequentially in inflorescence, and then bend downwards slowly after flowering. The bending speed of florets was mainly influenced by pollination, and bending angle increased with the prolongation of flowering time, while the pollen germination rate, stigma receptivity and nectar secretion has a rhythm of “low-high-low” during the whole period with the time going. The visiting frequency of all the four species of pollinators on upward flowers was significantly higher than that of downward flowers, and they especially prefer to visit flowers with a bending angle of 30°–60°, when the flowers was exactly of the highest flower rewards (nectar secretion and number of pollen grains), stigma receptivity and pollen germination rate. The seed set ratio and fruit set ratio of upward flowers were significantly higher than downward flowers, but significantly lower than unmanipulated flowers. Our results indicated that the T. repens could increase female and male fitness by accurate pollination. The most suitable flower angle saves pollinators’ visiting energy and enables them to obtain the highest nectar rewards. This coordination between plants and pollinators maximizes the interests of them, which is a crucial factor in initiating specialized plant-pollinator relationships.     

Effects of flowering plant density on pollinator visitation, pollen receipt, and seed production in Delphinium barbeyi (Ranunculaceae)

Variation in flowering plant density can have conflicting effects on pollination and seed production. Dense flower patches may attract more pollinators, but flowers in those patches may also compete for pollinator visits and abiotic resources. We examined how natural and experimental conspecific flowering plant density affected pollen receipt and seed production in a protandrous, bumble bee-pollinated wildflower, Delphinium barbeyi (Ranunculaceae). We also compared floral sex ratios, pollinator visitation rates, and pollen limitation of seed set from early to late in the season to determine whether these factors mirrored seasonal changes in pollen receipt and seed production. Pollen receipt increased with natural flowering plant density, while seed production increased across lower densities and decreased across higher flower densities. Experimental manipulation of flowering plant density did not affect pollinator visitation rate, pollen receipt, or seed production. Although pollinator visitation rate increased 10-fold from early to late in the season, pollen receipt and seed set decreased over the season. Seed set was never pollen-limited. Thus, despite widespread effects of flowering plant density on plant reproduction in other species, the effects of conspecific flowering plant density on D. barbeyi pollination and seed production are minor.     

Relative importance of diurnal and nocturnal pollinators for reproduction in the early spring flowering shrub Stachyurus praecox (Stachyuraceae)

Generalized pollination systems may be favored in early spring flowering plants, as during this period pollinator activity is unpredictable. Many previous studies have concentrated on the importance of diurnal visitors in pollination, and consequently, information on the contribution of nocturnal visitors to pollination in early spring is limited. This study was conducted to evaluate the relative importance of diurnal and nocturnal pollinators in the early spring flowering dioecious shrub Stachyurus praecox (Stachyuraceae), in two temperate forests in central Japan. Visitors to the female and male flowers were observed during day and night, and their relative contributions to seed set were compared. The pollinator observations revealed that the diurnal and nocturnal insects visited both male and female flowers, and that the main flower visitors were diurnal small bees and flies as well as nocturnal settling moths. The diurnal and nocturnal flower visitors also acted as pollinators, as the pollen grains of S. praecox were attached to the insects collected from the female flowers. Pollination experiments demonstrated that the contributions of diurnal pollinators to the seed set were higher than those of the nocturnal pollinators. The results of this study indicate that S. praecox has a generalized pollination system, comprising both diurnal insects and nocturnal settling moths. Although the roles of diurnal insects are more important in the pollination of S. praecox, nocturnal settling moths may have a complementary role in early spring.     

Change of floral orientation affects pollinator diversity and their relative importance in an alpine plant with generalized pollination system,Geranium refractum (Geraniaceae)

Floral orientation may affect pollinator attraction and pollination effectiveness, and its influences may differ among pollinator species. We, therefore, hypothesized that, for plant species with a generalized pollination system, changes in floral orientation would affect the composition of pollinators and their relative contribution to pollination. Geranium refractum, an alpine plant with downward floral orientation was used in this study. We created upward-facing flowers by altering the flower angle. We compared the pollinator diversity, pollination effectiveness, and pollinator importance, as well as female reproductive success between flowers with downward- and upward-facing orientation. Results indicated that the upward-facing flowers were visited by a wider spectrum of pollinators (classified into functional groups), with higher pollinator diversity than natural flowers. Moreover, due to influences on visitation number and pollen removal, the pollinator importance exhibited by the main pollinator groups differed between flower types. Compared with natural flowers, the pollination contribution of principal pollinators (i.e., bumblebees) decreased in upward-facing flowers and other infrequent pollinators, such as solitary bees and muscoid flies, removed more pollen. Consequently, stigmatic pollen loads were lower in upward- than in downward-facing flowers. These findings reveal that floral orientation may affect the level of generalization of a pollination system and the relative importance of diverse pollinators. In this species, the natural downward-facing floral orientation may increase pollen transfer by effective pollinators and reduce interference by inferior pollinators.