雌雄异熟植物露蕊乌头开花时间对雌雄功能期及表型性别的影响

开花时间决定了植物雌雄功能的交配机会, 最终影响繁殖成功。交配环境假说认为雌雄异熟植物开花时间的差异能引起植物表型性别的变异, 改变种群内的交配环境, 影响植物对雌雄功能的最佳性分配。为了研究开花时间对雌雄异熟植物的雌雄性别时期及表型性别的影响, 本文以毛茛科雄性先熟植物露蕊乌头(Aconitum gymnandrum)为实验材料, 记录了雄性和雌性功能期, 分析了植株开花时间、花的雌雄功能期和表型性别的关系。结果表明: 在植物同一花序内, 较晚开放的花有更长的雄性期和更短的雌性期, 性分配在时间上偏雄。雌雄功能期在时间上的相对分配随植物开花时间的变化表现出相似的趋势： 较晚开的花或较晚开花的个体, 花的雄性功能期相对于雌性功能期更长, 在时间上更偏向雄性功能。而且, 开花时间的差异影响种群内花的性比和植物个体的表型性别动态。随着开花时间由早到晚的变化, 种群内早期以雄花为主,末期以雌花为主, 种群内性别环境由偏雄向偏雌变化, 因此植株个体的平均表型性别则从偏雌转向偏雄。本文结果支持交配环境假说, 雄性先熟的露蕊乌头开花早期, 种群内花的性别比偏雄, 种群表型性别环境偏雄, 因而植物个体平均表型性别偏雌, 性别分配(即时间分配)偏向雌性功能, 而晚开花个体的平均性别偏雄, 更偏向雄性功能的分配。     

二重雌雄异型异熟物种色木槭3种表型花的细胞形态学研究

二重雌雄异型异熟,即雌雄功能按雄-雌-雄顺序分别表达,是有花植物中较为少见的异熟机制.槭属(Acer)大部分物种具有二重雌雄异型异熟的开花物候,且第一期雄花与第二期在形态上差别较大.为深入探讨花发育模式对花形态和开花物候的影响,本文应用石蜡切片技术和光镜技术,对色木槭(Acer mono)各个发育时期的3种类型花(雄花...     

楠木名称考订

<正> 经过多年对楠木的研究,我们发现楠木的正确学名应该修订。驰名中外的“楠木”,是很有趣的珍贵树种,它包括樟科润楠属(Machilus Nees)和楠属(Phoebe Nees)植物的一些近缘种,在四川及云南,一般把Phoebe zhennan,Phoebe hui和Machilus pingii通称为楠木,而在福建、浙江、贵州及广东、广西,却把Phoebe bournei称为楠木。自1877年英人A.Davenport在Kew Report报道了关于中国楠木的消息后,楠木的名称开始在植物学界造成乱混。D.Oliver于1879年把A.Davenport、E.Bradford和F.Vincot     

两种姜科花柱卷曲性植物柱头的位置与其可授性的关系

花柱卷曲性是一种见于姜科山姜属(Alpinia)和砂仁属(Amomum)植物中的独特的性二态现象, 具有这一性系统的植物, 其居群包括上举型和下垂型两种表型, 所有个体的雌雄性别功能在时间和空间上分离。本研究通过操控授粉和花粉管生长两项实验, 探讨花柱卷曲性植物个体两性功能的隔离方式及其适应意义。云南草蔻(Alpinia blepharocalyx)操控授粉实验表明, 自花花粉对其异交率影响不显著(P > 0.05), 但可能由于自花花粉沉降导致胚珠贴现进而引起近交衰退, 操控条件下每果结籽数显著减少(P < 0.01)。云南草蔻和红豆蔻(Alpinia galanga)花粉管生长实验都显示无论对两种表型进行怎样的授粉处理, 花粉粒萌发和花粉管生长的速率仅在柱头处于可授位置时表现出最大值, 与自交和异交授粉方式无关; 上举型植株上午花粉囊虽未裂但其内花粉已成熟。研究结果表明即使不考虑花柱运动, 山姜属植物也具有异型雌雄异熟的特性。这一结果证实了花柱卷曲运动机制是通过互补式雌雄异位和异型雌雄异熟相结合形成的花部二态性, 异型雌雄异熟促进了异交, 而花柱运动的功能可能在于避免雌雄干扰。     

多年生龙胆属植物个体大小与花期资源分配研究

于各物种花中前期对青藏高原东部高寒草甸6种多年生龙胆属植物花期的繁殖分配和性分配进行分析,结果表明:(1)多年生龙胆属植物的植株个体越大,繁殖投入越高,繁殖分配越低;(2)随着植物个体的增大,对雌性、雄性和吸引结构的投入都在增加,这可保证资源的充分利用,不会因为单一部分的增加而造成资源的浪费;(3)6种龙胆属植物中,有4种其性分配结果与性别分配(SDS)的理论预测一致,即大个体更偏向雌性器官的资源投入,但麻花艽(Gentiana atraminea)和达乌里秦艽(Gentiana dahurica)的性分配与个体大小则没有表现出负相关,可能与其本身具有的雌雄异熟———雄性先熟特点有关;(4)资源在雌雄功能间的分配没有表现出权衡关系,可能是由于植物必须在许多不同生活史性状之间进行资源分配,而不是两两之间非此即彼.     

水稻亚种间杂种小穗败育的细胞学基础

本文对普通栽培稻不同品种种类型间杂种小穗败育的细胞学基础及雌性败育的过程进行了研究,结果表明：（１）引起杂种小穗败育的原因有胚囊败育、花粉败育、开花时花药不开裂和雌雄异熟。其中胚囊败育而丧失受精能力是引起低结实率的最重要的因素,开花时花药不开裂和雌雄异熟在一定程度上形成了雌雄性细胞时间和空间的隔离屏障。     

地质时期樟科植物花化石及其系统演化意义

该研究对地质时期樟科植物花化石的主要类群,即Androglandula、Lauranthus、Mauldinia、Neusenia、Perseanthus和Potomacanthus属分别从属和种的形态特征、分布、地层以及系统意义进行了论述,并结合现代樟科植物从地层和分布、花序类型、花部形态特征和显微构造特征进行了分析。结果表明:(1)樟科植物在中晚白垩纪期,已经起源于劳亚古陆的中纬度区域。(2)樟科植物的花序类型为Mauldinia属的侧生花序类型和假伞形花序类型。(3)花为3基数的两性花,花被片6枚排列为2轮,雄蕊12或6,排列为4、3或2轮,最内轮雄蕊不育,第三轮雄蕊基部常见一对附属腺体,雄蕊药室瓣裂,4或2药室,雌蕊为单心皮。(4)花被片上常有大量的油细胞、并列型气孔器和单细胞毛。该研究结果中樟科花化石的发现,为樟科植物的系统演化提供了古生物学的证据和资料。     

云南九种樟科植物种子的萌发及脱水耐性（英文）

种子库是对野生植物进行长期迁地保存的重要手段,但不适用于种子脱水敏感的植物。樟科植物中有不少为我国南方常见的重要经济林木,许多种类具有较高的生态及经济价值,但关于其种子萌发及脱水耐性等生物学方面的研究资料十分缺乏。本研究选取来源于5个属的9种樟科植物,对其种子休眠及萌发特性进行了初步的研究并利用100粒种子法原理确定其脱水耐性。结果表明樟树(Cinnamomum camphora)种子可能具有中度生理休眠;毛尖树(Actinodaphne forrestii)、倒卵叶黄肉楠(Actinodaphneo bovata)、米槁(Cinnamomum migao)、网叶山胡椒(Lindera metcalfiana var.dictyophylla)、香叶树(Lindera communis)及多果新木姜子(Neolitsea polycarpa)的种子具有浅生理休眠;阴香(Cinnamomum burmannii)及粉叶楠(Phoebe glaucophylla)的种子可能不具有休眠。全部9种樟科植物种子在脱水到2.86%~7.16%含水量后均失去全部活力;而保湿保存的种子含水量保持在17.32%~44.87%之间,仍保持全部或大部分活力;因此该研究涉及的9种樟科植物都是脱水敏感性种子,不适合传统的种子库保存方法。     

青藏高原特有植物祁连獐牙菜（龙胆科）的花综合征与虫媒传粉

雌雄异熟和异型花在一些被子植物中的共同存在被认为是一种有效避免两性花植物自交并促进异交的机制。本文报道青藏高原特有植物祁连獐牙菜Swertia przewalskii Pissjauk.的花同时具有雌雄异熟和异型花这两种特征。在此基础上,我们详细观察了该植物访花昆虫的访花行为,主要探讨这种促进异花传粉的机制是否能完全避免株内异花传粉的自交。繁育系统试验证明祁连獐牙菜单花套袋不结实,说明雌雄异熟和异型花的花特征完全避免了单花的自花传粉,自然结实必须依赖昆虫传粉才能完成。然而,该植物却是高度自交亲和的,因为人     

中亚热带樟科3种植物幼苗叶结构型性状的种间差异及其相关性

为了揭示植物叶功能性状对全球气候变化的响应和适应规律,以樟科3种植物幼苗为研究对象,将其人工采集的种子经低温沙藏并于温室培育,然后将幼苗移栽到野外同质园中自然生长,研究中亚热带樟科植物刨花楠(Machilus pauhoi)、香樟(Cinnamomum camphora)和闽楠(Phoebe bournei)两年生幼苗生长季节9种叶结构型性状的种间差异及其相关性。结果显示,(1)在3种植物幼苗中,香樟叶面积、叶厚度、叶体积、叶氮磷比最大,叶氮浓度最高,叶组织密度最小;闽楠叶组织密度、叶干物质含量最大,叶磷浓度最高,叶面积、叶体积、比叶面积、叶氮磷比最小,叶氮浓度最低;刨花楠比叶面积最大,叶厚度、叶干物质含量最小,叶磷浓度最低;3种植物幼苗的叶厚度之间均无显著差异。(2)Pearson相关分析和线性回归分析结果表明,樟科3种植物幼苗的叶面积与叶体积间呈极显著正相关(P0.01)、与叶干物质含量间呈极显著负相关(P0.01)、与叶磷浓度间呈极显著负相关(P0.01)、与叶组织密度间呈显著负相关(P0.05)、与叶氮浓度间呈显著正相关(P0.05);叶厚度与比叶面积间呈显著负相关(P0.05)、与叶干物质含量间呈显著正相关(P0.05);叶体积与叶组织密度间呈极显著负相关(P0.01)、与叶氮浓度间呈极显著正相关(P0.01)、与叶磷浓度间呈显著负相关(P0.05);叶组织密度与叶磷浓度间呈显著正相关(P0.05);比叶面积与叶干物质含量间呈极显著负相关(P0.01)、与叶磷浓度间呈极显著负相关(P0.01);叶干物质含量与叶磷浓度间呈极显著正相关(P0.01)。这表明在同质园中生长的刨花楠、香樟和闽楠幼苗的9种叶结构型性状表现出一定的种间差异,不同物种同一叶结构型性状指标的大小顺序、种间差异及其显著性不同;3种植物幼苗不同叶结构型性状之间的相关性及其显著程度也不同。本研究结果为揭示樟科3种植物幼苗叶功能性状对全球气候变化的响应和适应规律提供了基础数据。     

Synchronized dichogamy and dioecy in neotropicalLauraceae

In hermaphrodite neotropicalLauraceae a highly evolved dichogamous system is present which represents a kind of temporal dioecy. This system involves the existence of two flower morphs which are characterized by reciprocal phases of receptivity of the stigmas and pollen release. In some genera (Persea, Cinnamomum), nectar is produced as a reward for the flower visitors, while in other genera (Aniba, Clinostemon, Licaria), nectar is absent and pollen seems to be the only reward. This implies that in this case the flowers in the female stage must be deceptive flowers. In dioecious species of the generaOcotea andNectandra, both the male and female flowers attract the visitors with nectar. The pollen-ovule ratio of theLauraceae is comparatively low. — The type of reproductive system that characterizes theLauraceae, comprising functional dioecy, small, inconspicuously coloured flowers, pollination by small bees, and large, one-seeded fruits dispersed by birds, is quite prominent among trees of various families in the tropical lowland forest. The relationship between the different modes of flowering within theLauraceae and the causes for the correlation of their reproductive traits are discussed.     

Notes on the floral morphology in Vivianiaceae (Geraniales)

The functional floral morphology of the three genera of Vivianiaceae (= Ledocarpaceae, Geraniales), Rhynchotheca, Viviania and Balbisia, is compared. Likely pollination mechanisms are inferred from morphology and field observations. The flowers of Viviania are nectariferous and apparently zoophilous with nectar as the (primary) pollinator reward. Balbisia has pollen flowers without nectaries, its showy corolla indicates that it is also zoophilous with pollen as sole pollinator reward; bees were observed as flower visitors. One taxon (B. gracilis) may be anemophilous. Rhynchotheca has flowers without petals, with large, pendulous anthers and lacks nectaries. It shows synchronous mass flowering in its natural populations and is evidently anemophilous. A comparison with other Geraniales shows that nectar flowers with small anthers are likely the ancestral condition in Vivianiaceae. This suggests that the pollen flowers with larger anthers of Balbisia and Rhynchotheca may represent an apomorphic condition. The documentation of pollen flowers and anemophily in Vivianiaceae expands the range of known floral and pollination syndromes in Geraniales.     

Nectary structure and nectar presentation in Aloe castanea and A. greatheadii var. davyana (Asphodelaceae)

This paper deals with the nectary structure and nectar presentation of two species belonging to different sections of the genus Aloe: A. castanea (Anguialoe) and A. greatheadii var. davyana (Pictae). The development of the nectary was studied by means of bright field and fluorescence light microscopy and scanning electron microscopy (SEM) in three flower stages (young, intermediate, old). Both species have septal nectaries. In A. castanea, a subsidiary tissue, not present in A. greatheadii var. davyana, was found beneath the nectary epithelium. This tissue accumulated starch that was hydrolyzed during secretion. Starch was slightly accumulated around the nectary in A. greatheadii var. davyana. The distribution of chlorophyll in the ovary was also different in the two species. These anatomical differences are not, however, correlated with greater nectar production in A. castanea. In this species, the nectary seems to degenerate after secretion, while in A. greatheadii var. davyana no sign of degeneration was observed. Differences in nectar presentation among the two species may account for different pollinators visiting their flowers.     

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。     

Male-biased sex ratio and promiscuous pollination in the dioecious island treeLaurus azorica (Lauraceae)

Pollination ofLaurus azorica (Lauraceae), a dioecious Macaronesian tree, was studied. Male and female trees had the same size distribution. The population had 2.5 times as many male trees as females. In addition, males produced more flowers, and their inflorescences lasted longer. Individual flower lifetime and length of flowering season were the same in both sexes. Between the years of observation, one tree changed sex. Pollinators wereHalictinae bees and the flyTachina canariensis. The bees collected pollen and nectar and the fly collected nectar from both sexes. Both species visited other plants as well. The evolution of breeding systems inLauraceae is discussed.     

Blühverhalten und Bestäubungsbiologie vonCarludovica palmata (Cyclanthaceae) — ein ökologisches Paradoxon

In natural habitats ofCarludovica palmata (Colombia) numerous stingless bees (Meliponinae) were observed as pollen collectors at the inflorescences and were believed to be the pollinators of the entomophilous flowers. Male flowers surround female ones on the spadix in a regular fashion. At first, the filiform, strongly scented staminodia of the female flowers unfold. After they have dropped, the anthers open, and finally the male flowers fall to ground. Only then, the stigmata of the female flowers are exposed. Previous literature references on proterogyny and the drying-up of the stigmata prior to the male phase inCarludovica are in conflict with these observations on the course of anthesis and pollination.

     

Nectar exploitation by herbivores and their parasitoids is a function of flower species and relative humidity

In conservation biological control, diversification of the agro ecosystem with flowering vegetation is seen as an important tool to support the broad range of predators and parasitoids that require nectar and pollen sources to survive and reproduce. In order to identify flowering plants that provide suitable food sources for natural enemies without supporting the pest species, we analyzed the exploitation of 19 flowering plants by two important lepidopteran cabbage pests, Pieris rapae and Plutella xylostella, and their hymenopteran parasitoids, Cotesia glomerata and Diadegma semiclausum. The experiments were conducted at 90% r.h., while Pieris rapae was tested both at 45% r.h. and at 90% r.h. At 45 ± 5% r.h., corresponding with field conditions at which P. rapae is predominantly active, the butterfly was unable to feed on a number of exposed floral nectar sources whose nectar was successfully exploited at 90% r.h. The broader nectar exploitation by P. rapae at the high humidity is presumably explained by the resulting decrease in nectar viscosity. When comparing D. semiclausum and its herbivorous host P. xylostella, the herbivore exploited a broader range of plants. However, those plants that benefited both the parasitoid and the herbivore had a much stronger effect on the longevity of the parasitoid. The results from the accessibility bioassay suggest that flowers where nectar is not accessible can have a negative impact on insect survival presumably by stimulating foraging without providing accessible nectar. Our results underline the importance of considering species-specific environmental conditions when fine-tuning the choice of nectar sources to be used in conservation biological control programs.     

Pollination ecology ofOxalis violacea (Oxalidaceae) following a controlled grass fire

Vernal grass fires may encourage profuse flowering in clonal, colonies ofOxalis violacea. Long-styled colonies appear to be more floriferous than short-styled colonies and set a greater number of capsules. Individual flowers of both morphs live one or two days, change position on their respective pedicels and advertise nectar concealed at the base of the floral throat. AlthoughDiptera, Hymenoptera, andLepidoptera forage for nectar, bees (Andrenidae,Anthophoridae, Halictidae, andMegachilidae) probably make the only effective pollen transfers between the two morphs. Both male and female bees may transport pollen of both morphs and short-tongued bees (e.g.,Augochlorella spp.,Dialictus spp.) may be more common but as effective as pollinators as long-tongued bees (e.g.,Calliopsis andreniformis andHoplitis spp.). The conversion rate of flowers into capsules is only 13–17%. The spreading style in the short-styled morph is interpreted as an adaptation restricting insect-mediated, self-pollination but encouraging bee-stigma contact during nectar foraging.     

Sequential variation in the components of reproductive success in the distylousJasminum fruticans (Oleaceae)

A 2-year study of three natural populations of the distylousJasminum fruticans showed that mean fruit and seed production were significantly greater in shortstyled plants (thrums) than in long-styled plants (pins). In this study, we investigated the role of four sequential factors which may differentially influence fruit and seed set in the two floral morphs: (1) differences in flowering phenology, (2) a limitation of pollen transfer towards pins, (3) a differential capacity of the two morphs to act through famale and male function and (4) differential fruit abortion in the two morphs. Fruit set was significantly influenced by differences in flowering phenology although there were no differences in flowering time between the two morphs. supplementary pollinations in a natural population significantly increased fruit set and reduced the difference in fruit set between the two morphs in relation to controls, indicating a limitation on pollen transfer which was most severe towards pin stigmas. In reciprocal crosses, seed set was significantly dependent on the paternal and maternal identity of the pin parent. There was no significant variation among thrums for their performance as male or female parent. Furthermore, individual pin plants with relatively high percentage seed set as female parents gave poor seed set as male parents and vice-versa. Whereas fruit removal had no effect on seed number in thrum plants, a greater proportion of viable seeds were produced on pin plants which were left to naturally mature their fruits than on pins which had fruits artificially removed, suggesting the occurrence of selective fruit abortion in pins but not in thrums. The initially greater maternal fitness of thrums due to their greater success as pollen recipients may thus be opposed by increased viable seed set in the pins due to factors acting after the pollination stage. The relative reproductive success of floral morphs in the distylousJ. fruticans is thus differentially influenced by ecological factors occurring at different stages of the reproductive process.     

Flower choice by honey bees (Apis mellifera L.): sex-phase of flowers and preferences among nectar and pollen foragers

Bees foraging for nectar should choose different inflorescences from those foraging for both pollen and nectar, if inflorescences consist of differing proportions of male and female flowers, particularly if the sex phases of the flowers differ in nectar content as well as the occurrence of pollen. This study tested this prediction using worker honey bees (Apis mellifera L.) foraging on inflorescences of Lavandula stoechas. Female flowers contained about twice the volume of nectar of male flowers. As one would predict, bees foraging for nectar only chose inflorescences with disproportionately more female flowers: time spent on the inflorescence was correlated with the number of female flowers, but not with the number of male flowers. Inflorescence size was inversely correlated with the number of female flowers, and could be used as a morphological cue by these bees. Also as predicted, workers foraging for both pollen and nectar chose inflorescences with relatively greater numbers of both male and female flowers: time spent on these inflorescences was correlated with the number of male flowers, but not with the number of females flowers. A morphological cue inversely associated with such inflorescences is the size of the bract display. Choice of flowers within inflorescences was also influenced predictably, but preferences appeared to be based upon corolla size rather than directly on sex phase.