欧报春二型花柱的繁育特性研究

二型花柱植物通常具有自交不亲和性,在不同植物中所表现的可育性不同。欧报春(Primula vulgaris)是典型的二型花柱植物,为了探究欧报春的繁育特性,通过温室栽培,对欧报春的长花柱和短花柱的花部特征、花粉和花柱形态、花粉活力、柱头可授性、花粉/胚珠比、杂交指数、杂交亲和性、花粉管观察进行研究。结果表明,(1)长花柱和短花柱的花冠直径、花冠筒长度、柱头高度、花药高度和花筒中部直径均表现出两型性;(2)花粉和柱头观察发现花粉极轴长、花粉赤道轴长、花柱直径、柱头乳突细胞和花粉数量均有差异;(3)长花柱的花粉/胚珠比为384.20,短花柱为369.70,属于兼性异交类型;长花柱和短花柱的花粉活力和柱头可授性能在较长时间内维持较高活力;(4)长花柱杂交指数值为5,短花柱为4,表明繁育系统类型为异交,部分自交亲和,需要传粉者;6种授粉组合均能结实,异型花间授粉的结实数明显高于同型自花授粉和异株同型授粉;短花柱为母本的异型花间授粉组合亲和性优于其他组合;欧报春存在自交不亲和性,长花柱的自交不亲和性低于短花柱。     

小报春不同授粉组合亲和性研究

利用小报春‘红星’、‘紫霞’、‘罗兰香’3个品种分别设置8种授粉组合,统计了不同授粉组合的结实情况和单果种子数量,并对‘红星’品种部分授粉组合的花粉萌发与花粉管伸长过程进行荧光显微观察。结果显示:(1)3个品种的结实率和单果种子数量均表现为异型植株授粉>长花柱同型异株授粉、长花柱自交>短花柱同型异株授粉、短花柱自交,不同授粉组合间单果种子数量差异极显著,异型植株授粉类型结实率均达到100%,单果种子数量为44～181粒,显著高于自交组合和同型异株杂交组合;以异型致死花粉作为蒙导对短花柱同型异株授粉组合的结实有一定促进作用,但对长花柱同型异株授粉组合的结实没有一致的促进作用;3个品种中‘红星’的结实率和单果种子数量最高。(2)荧光显微观察表明,异型授粉组合花粉在柱头上大量萌发并在花柱中伸长,授粉144h后花粉管开始进入子房;同型授粉组合授粉12h后花粉开始萌发,但直到授粉后144h花粉管还没有进入花柱;自交授粉组合授粉后144h仍无花粉萌发。实验结果说明,小报春存在明显的自交不亲和性,且短花柱类型的自交不亲和性比长花柱类型强。     

二型花柱植物愉悦蓼的繁殖生态学研究

愉悦蓼具有典型的二型花柱现象。通过统计安徽部分地区愉悦蓼长、短柱花花型数量、柱头和花药高度差及结实率;观察愉悦蓼的长、短柱花的型比;结合苯胺蓝染色鉴定愉悦蓼长、短柱花的花粉与柱头的亲和性。结果表明,愉悦蓼长、短柱花的型比符合1∶1;长柱花的结实率较大;自花授粉组合中的花粉在柱头上也能萌发出花粉管,但不能到达子房。     

梅花个体内花柱长度的变异及其对繁殖成功的影响

植物个体内花型的变异影响繁殖成功, 雌性繁殖性状的变异可能影响雌性的繁殖成功, 也可能作为花粉的受体影响雄性的繁殖成功。然而, 植物个体内不同花柱长度的花产生的花粉是否影响植物的繁殖成功却少有研究。梅(Armeniaca mume)是原产我国的重要木本花卉和经济果树, 我们的野外观察发现在同一植株内, 不同花的花柱长度有变异, 存在长柱型、短柱型和雄花型(雌蕊败育)三种花型, 是比较雌性繁殖性状的变异对两性繁殖成功的影响的理想材料。本文主要测量了不同花型的花部特征, 统计花期, 并开展体外花粉萌发以及人工控制授粉实验。结果表明: 长柱型的花冠直径、雌蕊长、单花花粉数、花粉体积显著大于短柱型和雄花型。长柱型的单花期以及雌花期显著长于短柱型。长柱型、短柱型以及雄花型花粉在活体柱头上的萌发率没有显著性差异, 雄花型的花粉管长度显著高于长柱型和短柱型。长柱型为母本的花粉萌发率以及花粉管的长度要显著高于短柱型。长柱型、短柱型、雄花型花粉授粉与自然对照处理的坐果率没有显著性差异, 而长柱型为母本的坐果率要显著高于短柱型为母本的坐果率。这些结果表明野生梅花的长柱型为母本有利于花粉的萌发和花粉管的伸长, 有高的坐果率; 但其作为花粉供体的雄性功能与其他花型没有差异。     

艳丽耳草的二型花柱及异型自交不亲和系统

异型花柱是一种受遗传因素控制的花型多态性现象,包括二型花柱和三型花柱两种类型.本文以茜草科艳丽耳草(Hedyotis pulcherrima)为实验材料,通过对其野外居群的花型、花部形态及花粉特征等观察,发现艳丽耳草野外居群同时存在长花柱型花和短花柱型花,长/短花柱型花的数量比例为1∶1.两型花具有精确的交互式雌雄异位特征,并且该特征与花冠长度相关性显著.长/短花柱型花的柱头裂片长度、花粉大小及淀粉含量等具有二型性.花粉体外培养时花粉萌发率及花粉管生长速率无显著性差异.人工授粉后,艳丽耳草长/短花柱型花型间异交花粉管生长形态正常,授粉24 h后花粉管均已进入子房.而长/短花柱型花在自交及型内异交下均表现为不亲和,花粉管生长停止于柱头,花粉管顶端累积胼胝质并膨大.艳丽耳草没有无融合生殖现象,型间人工辅助异交授粉结实率为100％,显著高于自然结实率.本研究结果表明,艳丽耳草是典型的二型花柱植物,并具有异型自交不亲和系统.     

青篱柴通过促进亲和花粉生长而提高传粉精确性

异型花柱植物的适应意义在于提高亲和花粉的传递, 从而促进异交, 但是有不少研究发现柱头上落置了大量不亲和花粉。目前, 很少有人研究柱头是否有利于亲和花粉的萌发和花粉管伸长, 以及通过去雄处理排除花内和植株内不亲和花粉干扰从而验证二型花柱植物是否可以促进异交。本研究以亚麻科青篱柴属(Tirpitzia)的二型花柱植物青篱柴(T. sinensis)为研究对象, 分居群调查了青篱柴长、短柱型的植株数量, 测量不同柱型的花粉与柱头大小以及观察其表面纹饰, 测定不同开花时间长、短柱型的柱头活性与花粉活力, 统计自然状态下柱头上落置的不同表型花粉比例, 进一步统计花内、株内去雄和自然对照下柱头上落置的不同表型花粉比例, 计算型间、型内和混合授粉花粉管长度和花粉萌发率, 人工授粉检测其是否型内异交不亲和与自交不亲和。结果表明, 自然居群中长、短柱型青篱柴植株数量没有显著性差异; 短柱型青篱柴花粉体积显著大于长柱型, 且二者花粉表面纹饰不同, 但不同柱型的柱头表面积与表面纹饰无差异; 青篱柴开花第一天的花粉活力显著高于开花第二天, 而柱头活性在开花前两天无显著性差异; 自然状态下柱头上落置的不亲和花粉比例显著高于亲和花粉; 在长柱型青篱柴中, 花内和株内去雄显著提高了柱头上亲和花粉的落置比例; 柱头上授型内花粉, 其花粉萌发率和花粉管的长度都显著低于授型间花粉; 授粉结果表明青篱柴为型内异交不亲和与自交不亲和。二型花柱植物通过促进亲和花粉的萌发和花粉管的伸长而有利于型间授粉, 从而显著提高其传粉精确性。     

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。     

‘晚大新高’梨授粉及受精过程的显微动态研究

应用荧光显微法和石蜡切片解剖法对‘晚大新高’梨授粉受精过程进行了系统观察研究。结果表明：‘晚大新高’梨自花授粉不结实;异花最佳授粉品种为‘黄花’,其次为‘翠冠’和‘丰水’。与选用‘黄花’为异花授粉品种相比,自花和异花的授粉受精过程存在明显差异,自花花粉在授粉后2h开始萌发,8h花粉管生长至离柱头约1／3处停止生长,顶端膨大呈球形,表现出自交不亲和性;异花花粉在授粉后1h开始部分萌发,8h花粉管生长至花柱中部,24h到达花柱基部并进入子房,48h进入胚囊,72h完成双受精过程。     

安徽特有植物安徽羽叶报春的繁殖生物学研究

本文分别从物候、繁育结构和传粉等方面研究了国家三级保护植物、安徽特有种——安徽羽叶报春(Primula merrilliana)的繁殖生物学特征。研究结果表明:(1)安徽羽叶报春是典型的形态和功能意义上的花柱二型的二年生植物,其始苗期为9月,一直持续到第二年6月底或7月初死亡,各居群长柱花植株比短柱花植株开花略早3-5d;(2)安徽羽叶报春的散孔型花粉显示其在报春花属中有重要的系统意义和进化意义。同时,短柱花花粉量比长柱花少,但其花粉直径是后者的1.78倍左右;(3)长花柱的雌蕊长度是短花柱的1.64倍,而且其柱头上的乳头状突起比短花柱上的长而稀;(4)3个研究居群的P/O比都不相同,我们发现花粉量比胚珠数量有更大的变异,这可能与生境有关;(5)安徽羽叶报春为异花授粉植物,蓟马属(Thrips)昆虫为其重要的传粉者,其同型花授粉可育性远比异型花授粉的高;(6)其长、短柱型种子没有明显的形态差异,多属不等边七面体,少为其他多面体。据研究,在小居群中两种花柱类型植株的比例失衡,生境的破坏和伴生种的消失可能是导致安徽羽叶报春濒危的重要原因。     

绣球茜的二型花柱及其传粉生物学初步研究

首次对绣球茜(Dunnia sinensis Tutch)的花药和柱头高度、花粉和柱头形态,以及人工辅助授粉的结实情况等进行了研究.结果表明:绣球茜在同一居群中同时具有长花柱(Pin 型)和短花柱(Thrum)两种花型,长花柱植株的柱头和雄蕊高分别为9.61±0.36 mm和6.79±0.38 mm,短花柱则为6.11±0.56 mm和8.96±0.59 mm,表现出互补式雌雄异位的花部特征.通过人工辅助授粉,两种花型植株的自交和同型植株间异交都不结实,仅在型间异交方能正常结实,说明绣球茜中存在极强的自交不亲和和型内不亲和现象.在花粉与柱头形态方面:长柱型花的单花花粉量(38555.6±6258.4)显著地小于短柱型花(52145.45±8924.5)(t=4.009,P＜0.01),长柱花和短柱型花的胚珠数分别为38.73±1.85和39.1±2.25(t=-4.13,P＞0.01);长柱型花花粉粒的大小(极径21.27±0.70 μm)显著地小于短柱花(21.92±0.79μm)类型(t=3.890,P＜0.01),而柱头乳突大小长柱类型要大于短柱类型,表现出明显的二型性.研究结果表明绣球茜是一种典型的二型花柱植物.此外,对其传粉昆虫及昆虫访花行为的观察表明,蝶类(青风蝶属Graphium)和蜂类(熊蜂Bombus sp.和木蜂Xylocopa magnifica Smith)为绣球茜的主要访花昆虫和传粉昆虫,它们能够在两种不同花型植株之间有效地传粉.     

Pollination biology and the impact of floral display, pollen donors, and distyly on seed production in Arcytophyllum lavarum (Rubiaceae)

In animal-pollinated plants, two factors affecting pollen flow and seed production are changes in floral display and the availability of compatible mates. Changes in floral display may affect the number of pollinator visits and the availability of compatible mates will affect the probability of legitimate pollination and seed production. Distyly is a floral polymorphism where long-styled (pin) and short-styled (thrum) floral morphs occur among different individuals. Distylous plants frequently exhibit self and intra-morph incompatibility. Therefore changes in morph abundance directly affect the arrival of compatible pollen to the stigmas. Floral morph by itself may also affect female reproductive success because floral morphs may display differences in seed production. We explored the effects of floral display, availability of neighboring compatible mates, and floral morph on seed production in the distylous herb ARCYTOPHYLLUM LAVARUM. We found that floral display does not affect the mean number of seeds produced per flower. There is also no effect of the proportion of neighboring legitimate pollen donors on seed production in pin or thrum flowers. However, floral morphs differed in their female reproductive success and the thrum morph produced more seeds. Hand pollination experiments suggest that differences in seed production between morphs are the result of pollen limitation. Future research will elucidate if the higher seed production in thrum flowers is a consequence of higher availability of pollen donors in the population, or higher efficiency of the pin morph as pollen donor.     

Reproductive conflicts ofPalicourea padifolia (Rubiaceae) a distylous shrub of a tropical cloud forest in Mexico

We studied a population of the distylousPalicourea padifolia (Rubiaceae) in a cloud forest remnant near Xalapa City, Veracruz, México to explore possible asymmetries between floral morphs in the attractiveness to pollinators, seed dispersers, nectar robbers, floral parasites, and herbivores. We first assessed heterostyly and reciprocal herkogamy by measuring floral attributes such as corolla length (buds and open flowers), style and anther heights, stigma and stamen lengths and the distance between the anther tip to the stigma lobe. We then estimated floral and fruit attributes such as flower size, anther height, number and size of pollen grains, fruit size, seed size, nectar production, and flower and fruit standing crops to assess differences between floral morphs in attracting and effectively using mutualistic pollinators and seed dispersers. Also, floral parasitism and nectar robbing were assessed in this study as a measure of flower attractiveness to antagonists. The system seems to conform well to classical heterostyly (e.g. reciprocal stamen/style lengths, pollen and anther dimorphism, intramorph incompatibility) yet, there were several tantalizing differences observed between pin and thrum morphs. Thrum flowers have longer corollas and larger but fewer pollen grains than pin flowers. Both morphs produced the same total number of inflorescences, developed the same number of buds, and opened the same number of flowers per inflorescence during the flowering season. Nectar production and sugar concentration were similar between floral morphs but the reward was not offered symmetrically to floral visitors throughout the day. Nectar concentration was higher in pin flowers in the afternoon. The numbers of developing, fully developed, and ripe fruits were the same between floral morphs, however, fruits and seeds were larger than those of thrums. The incidence of fly larvae was higher among thrum flowers and damage by nectar robbing was the same between floral morphs. Fruit abortion patterns of flowers manually pollinated suggest intra-morph sterility (self and intramorph incompatibility). There were no differences between morphs in fruit and seed set per flower following legitimate pollination although thrums were more leaky than the pins (intramorph compatibility).     

Comparative reproductive biology of Primula merrilliana Schltr. and P. cicutariifolia Pax

The reproductive biology of Primula merrilliana Schltr. and P. cicutariifolia Pax that are sister taxa and the only two members of Primula sect. Ranunculoides were studied. The results showed that P. merrilliana is typically a distylous species not only in morphology but also in function; it has an incompatibility system that restricts the legitimate pollination to that between pin and thrum flower morphs, but self-fertilization may occur under certain conditions. P. cicutariifolia is self-compatible. The pin morph of P. merrilliana has longer stigma papillae and smaller pollen than the thrum morph. The results stated above support the view that P. filchnerae should be moved from sect. Pinnatae to sect. Auganthus.     

Asymmetry in pollen flow promotes gender specialization in morphs of the distylous neotropical herb <Emphasis Type="Italic">Arcytophyllum lavarum</Emphasis> (Rubiaceae)

Distyly is a floral polymorphism, characterized by a reciprocal positioning between stigmas and anthers in different flowers, where two floral morphs, long-styled (pin) and short-styled (thrum) occur within the population. Distyly is suggested as one of the routes leading to the evolution of separate sexes in plants. In this evolutionary pathway, pollinators may disrupt the complementarity of pollen transfer between morphs. Consequently, the floral morphs gradually specialize as either male or female. A key process required for gender specialization in distylous plants is a deviation of the realized functional gender (i.e. the proportion of genes transmitted to the next generation via pollen donation and seed production) from the potential functional gender (i.e. the expected contribution of male and female function to reproductive success from the number of ovules or pollen grains produced by each morph). I selected the distylous herb Arcytophyllum lavarum (Rubiaceae) to determine if asymmetry in pollen flow promotes differences in seed production, pollen donation and a discrepancy between the potential and the realized functional genders in pin and thrum floral morphs. Pollen flow in A. lavarum is asymmetric and the pin morph is more efficient at performing cross-pollination than the thrum morph. Conversely, the thrum morph produced two times more seeds than the pin morph. Male and female contributions to the potential functional gender were equivalent in both morphs. However, the pin morph transmitted more genes through pollen donation and the thrum morph more through seed production than expected from their potential functional genders. These results support the hypothesis that if pollinators consistently promote asymmetric pollen flow between morphs over generations, it is possible that gender specialization may evolve to the extreme of dioecism from an original distylous condition.     

Frequency-dependent variation in reproductive success in Narcissus: implications for the maintenance of stigma-height dimorphism

Negative frequency-dependent selection is a major selective force maintaining sexual polymorphisms. However, empirical demonstrations of frequency-dependent reproductive success are rare, particularly in plants. We investigate this problem by manipulating the frequencies of style morphs in a natural population of Narcissus assoanus, a self-incompatible herb with style-length dimorphism and intra-morph compatibility. We predicted that the reproductive success of morphs would vary negatively with their frequency because of the effects of morph-specific differences in sex-organ position on patterns of pollen transfer. This prediction was generally supported. The fruit and seed set of the two morphs did not differ significantly in plots with 1 : 1 morph ratios. However, short-styled plants produced significantly fewer seeds than long-styled plants in monomorphic plots, and significantly more seeds than long-styled plants in plots with 'long-biased' morph ratios. These patterns indicate that in the absence of physiological barriers to intra-morph mating, negative frequency-dependent selection contributes to the maintenance of stylar polymorphism through inter-morph pollen transfer. Our experimental results also provide insights into the mechanisms governing the biased style-morph ratios in populations of Narcissus species.     

Heterostyly inPrimula. 3. Pollen water economy: a factor in the intramorph-incompatibility response

Summary The pollens from pin (long-styled) and thrum (short-styled) flowers ofPrimula differ markedly in water economy. While pin pollen is little affected by atmospheric humidity, the germinability of thrum pollen in liquid medium is sensitive to the conditions experienced during the immediately preceding period, being depressed when the grains are partly desiccated, although capable of being restored with subsequent controlled rehydration. The tubes produced by incompletely rehydrated thrum pollen show abnormal growth forms, suggesting that the effect is on the membranes of the vegetative cell, a conclusion supported by observations on membrane state using the fluorochromatic reaction. Thrum pollen stripped of part of the material carried in the cavities of the exine by rinsing with a lipid solvent loses much of its capacity for the uptake of atmospheric water, indicating that, in this morph, some factor facilitating hydration is transferred from the sporophytic parent during pollen maturation.Implications of these differences in the physiology of the pin and thrum pollens for the functioning of the intramorph-incompatibility system are discussed.     

Fluorescence and scanning electron microscopic study on self-incompatibility in distylous Averrhoa carambola L.

Various combinations of intermorph, selfing and intramorph pollinations were carried out in Averrhoa carambola and the pollinated pistils were observed under fluorescence and scanning electron microscopes in time-course experiments. In both compatible and incompatible pollinations, similar behavior of pollen germination and penetration was observed in the first 4 h after pollination. In compatible intermorph pollination, pollen tubes were found at the base of the transmitting tract of the style at 8 h and 24 h after pollination in both the pin and thrum morphs. With thrum flowers, selfing resulted in pollen tubes being uniformly arrested at the junction between the stigmatic and stylar tissues. Penetration of pollen tubes into the upper portion of style was observed in thrum intramorph pollination and, when the second member was treated as the gynoecial tissue under the same pollination, penetration of tubes was further enhanced. Pin flowers, on selfing, resulted in pollen tube penetration farther down the style than was the case with thrum selfing. Intramorph pollination of pin morph behaved in a similar manner to selfing and was not affected by genotypes. Beside the stamen-style dimorphism, the receptive surface of the cob stigma was larger in pin than thrum flowers. While pin pollen was round, thrum pollen was oblong in shape with pin to thrum ratio on the polar axis being 1.2 and on the equatorial axis 0.8. The stigma of pin morph belonged to the dry type, while that of the thrum resembled the wet type.     

Pollen flow in the distylous<Emphasis Type="Italic"> Palicourea fendleri</Emphasis> (Rubiaceae): an experimental test of the Disassortative Pollen Flow Hypothesis

The Disassortative Pollen Flow Hypothesis proposed by Darwin postulates that the relative position of anthers and stigmas in distylous flowers enhances pollen flow between flowers of different morphs (legitimate pollination), in comparison to flow between flowers of the same morph (illegitimate pollination). In order to test this hypothesis, we measured pollen transport, mediated by a trained Copper-rumped Hummingbird (Amazilia tobaci), between flowers of the distylous Palicourea fendleri under laboratory conditions. In individual tests, we offered to the hummingbird a pollen donor flower and two emasculated recipient flowers in a controlled sequence. After each foraging bout, we counted the number of pollen grains transported from the donor flower to the stigmas of both recipient flowers. In agreement with Darwin's hypothesis, we found that hummingbirds transport pollen of "pin" flowers in significantly higher numbers to legitimate "thrum" stigmas, even if previously visiting a "pin" flower. However, "thrum" pollen was deposited in greater numbers on illegitimate "thrum" stigmas. We interpret this asymmetry largely as the consequence of floral morphology; pollen flow was greater between anthers and stigmas that exhibit greater spatial matching. In P. fendleri, the position of floral organs along the corolla tube does not always precisely correspond. In our experimental system, the probability that the pollinator extracts a pollen grain from the anther and the probability of self-pollination were both dependent on the type of floral morph. We discuss the relevance of the latter findings in relation to other studies of pollen flow in heterostylous species.