不同海拔藜芦种群繁殖特征的初步研究

 在北京东灵山地区,沿一定海拔梯度,对藜芦（Veratrum nigrum）这一雄花两性花同株的多年生草本植物的繁殖特征进行了初步研究。结果表明：藜芦开花植株的生物量显著大于未开花植株的生物量。藜芦开花植株大小存在最小临界值,总种群的最小临界值为2.61 g,不同种群的繁殖临界值存在一定的差异。根据花粉/胚珠比（Pollen / ovule ratio,P/O比）推测,藜芦应属于以异交为主的混合交配系统。雄花的大小与生物量都比两性花小,而且其开放时间也晚于两性花,但二者的花粉生产量却没有显著差异。这种现象与人们针对雄花两性花同株植物的雄花功能所提出的最优资源分配假说（Optimal resource allocation hypothesis）是一致的。     

Dioecy inHonkenya peploides var.major (Caryophyllaceae)

Sexual difference and pollination system inHonkenya peploides var.major were investigated. The present analyses indicate that sex expression of this plant is functionally dioecious, rather than androdioecious, as described previously. Its flowers are largely pollinated by small bees, hover-flies, flies, and ants. Female flowers were morphologically characterized by conspicuously longer styles and smaller petals, and had no pollen grains, while male flowers had shorter styles, larger petals, and longer filaments, and produced viable pollen grains. Although the male flowers possess many ovules in an ovary, they set fruits at a very low frequency in natural conditions and did not produce fruits by pollination experiments. We suggest that the dioecy of this species has been derived from hermaphrodite through gynodioecy, and not directly from hermaphrodite.     

Fruit set increases with maleness in the andromonoecious Acacia caven

In long-lived plants, sexual expression can be highly variable in time and space. The extent to which sexual dimorphism of flowers is expressed in the same or in separate individuals, may have implications for the plants’ dependence on pollen vectors, the compatibility of the pollen received, and the potential for setting fruit. Here, we account for variability in sexual expression in the small tree Acacia caven, which produces hermaphrodite and male flowers on the same or in separate individuals. We focus on whether individual sexual expression influences fruit set, which latter has been reported to be extremely low in this species. Individual sexual expression, estimated as the hermaphrodite: male flowers ratio was variable both within and among plants across two reproductive seasons. Though male flower production could be very high (up to 99% of the flowers), all trees produced both flower types within the same individual, thus confirming andromonoecy in this species. More interestingly, hermaphrodite: male flowers ratio had a negative effect on fruit set. This pattern was consistent across two reproductive seasons and suggests that maleness should favor female function. Similar trends found in other plant species with the same sexual system support the hypothesis that male flowers of andromonoecious species may contribute to reduce self-pollen interference compared with hermaphrodite flowers. By favoring the deposition of compatible pollen grains and increasing fruit set, maleness would then help to maintain andromonoecy in this and other andromonoecious species.     

Yield improvement through female homosexual hybrids and sex genetics of sweet gourd (<Emphasis Type="Italic">Momordica cochinchinensis</Emphasis> Spreng.)

The present research aimed to evaluate the effect of silver nitrate (AgNO₃) on sex modification in sweet gourd (Momordica cochinchinensis Spreng.), and to explore the possibility of sexual crossing between two genetically female plants. Spray applications of AgNO₃ on 30 days’ old female plants induced hermaphrodite flowers. Male plants were insensitive to the AgNO₃ sprays. Application of 500 mg/l AgNO₃ on female plants produced the maximum proportion of induced hermaphrodite flowers. Hermaphrodite flowers appeared 17–21 days after AgNO₃ spray and continued up to 8–17 days, depending upon the concentration of AgNO₃. Pollen grain viability of induced hermaphrodite flowers (93.5%) was similar to pollen grain viability of normal male (95.0%) flowers. Because of higher fruit weight, progenies from female homosexual cross recorded higher yield. The hybrids from such crosses produced only female plants while the hybrids between female and normal male segregated into male and female in an equal proportion, indicating that sex in sweet gourd is controlled by a single factor, male being heterozygous and female being homozygous recessive. Through this technique, elite characters of female genotypes could be combined into a single plant.     

澜沧舞花姜繁殖生物学特性及其进化意义探讨

 舞花姜属（Globba）植物具有多样的繁殖策略。分布于西双版纳的澜沧舞花姜（Globba lancangensis）自然条件下既能结实,同时又能在花序下部产生珠芽。通过对澜沧舞花姜的花部性状、花粉活力、传粉昆虫的访花行为、结实状况、珠芽产量等多方面的观测,初步了解了澜沧舞花姜的繁殖生物学特性。结果表明,澜沧舞花姜具有雄花及两性花同株的性表达特征。雄花及两性花的花粉在中午12∶00以前活力很高,之后雄花的花粉活力急剧下降,而两性花的花粉到16∶00仍有萌发能力。澜沧舞花姜在花序上产生雄花及两性花,每个花序每天仅开少量的花,其中50%的时间仅开雄花或两性花,在整个种群中形成了一定程度的暂时性的雄花两性花异株现象,从而增加了异交的可能性。澜沧舞花姜雄花的存在为P/O低的两性花提供了花粉补贴,这使得它可以通过调节雄花与两性花比例来调节种群的P/O,从而保证一定的结实能力。人工自交与异交下结果率没有差异,但自交结实率显著低于异交结实率,表明澜沧舞花姜有明显的自交不亲和现象。排蜂（Megapis dorstata）和黄绿彩带蜂（Nomia strigata）是澜沧舞花姜的主要访花昆虫,其中排蜂是它的有效传粉昆虫。澜沧舞花姜可能通过雄花两性花同株与自交不亲和相结合来促进异交。     

冠果草的性表达状态及其进化含义

通常认为雄花两性花同株是植物性表达两性花进化到雌雄异株的过渡类型之一。慈姑属仅冠果草（Ｓａｇｉｔｔａｒｉａ ｇｕｙａｎｅｎｓｉｓ Ｈ．Ｂ．Ｋ．ｓｕｂｓｐ．ｌａｐｐｕｌａ（Ｄ．Ｄｏｎ）Ｂｏｊｉｎ）的性表达为典型的雄花两性花同株,其他种为雌雄同株。对冠果草野外和实验居群的性配置进行了定量观察。东乡和武夷山居群雄花的比例分别为２．４８％０．９６％。实验表明,栽培条件影响冠果草的性表达：在营养较好的条件下     

Sex Expression and the Evolutionary Advantages of Male Flowers in an Andromonoecious Species, Sagittaria guyanensis subsp. lappula (Alismataceae)

Sex expression in Sagittaria guyanensis H.B.K. subsp. lappula (D. Don) Bojin is typically andromonoecious while the other species in the same genus are basically monoecious. The evolutionary advantages of male flowers and hermaphrodite flowers in S. guyanensis subsp. lappula were assessed by measuring sex allocation and pollen movements in two wild populations of the species. Two cultivated populations served as controls. The percentage of male flowers was very low in the two wild populations in Dongxiang, Jiangxi Province and Wuyishan, Fujian Province, viz., 2.48% and 0.96% respectively. In the two cultivated populations, male flower percentage significantly increased when the soil was of higher nutrient content. This indicates that the allocation to male versus female reproduction might change in response to environmental factors. Pollen production per male flower was 4.1 times higher than that of a hermaphrodite flower. The floral shape and size of male and hermaphrodite flowers were similar. No difference was observed between these dimorphological flowers in pollen germination rate in vitro and in the speed of pollen tube growth in vivo. Anthesis was only 4-5 h. Male flowers usually opened 0.5 h earlier than hermaphrodite flowers. An unexpected finding was that no pollen from the male flowers was found on the stigmas of the hermaphrodite flowers, in spite of the occasional visits by insects to both types of flowers in both wild and control populations. A consistent pattern of fruit development was found to exist in open pollinated flowers as well as in flowers that had been bagged. The sex ratios did not have significant influence on fruit set. Approximately 25% of the pistils in a gynoecium failed to develop into fruits because no pollen was deposited on them, indicating that the fruit set of this andromonoecious plant is mainly affected by pollen limitation rather than resource limitation. Reproduction in S. guyanensis subsp. lappula in the habitats was dependent on self-pollination in hermaphrodite flowers. The male flowers in this species might be a potential source of additional pollination and may facilitate cross-pollination. The fact that the flowers of monoecious species in Sagittaria pollinated by a wide diversity of insect visitors may contribute enormously to the diversification of sex expression in this genus.     

Reproductive biology of Lactoris fernandeziana (Lactoridaceae)

Lactoris fernandeziana, monotypic in its family, is endemic to the cloud forests of Robinson Crusoe Island. Although there has been considerable study of the relationships of Lactoris, as a rare species and as a putative primitive paleoherb, little is known of its reproductive biology. Knowledge of the latter is essential for effective conservation programs. The species is gynomonoecious. The overall proportion of flowers is ∼1 female:1 hermaphrodite. The inconspicuous semipendulous green flowers, usually in mixed-gender inflorescences, do not produce rewards. Hermaphrodite flowers are herkogamous and protogynous. Pollen grains are shed from the extrorse anthers in permanent dry tetrads. There is a mean of 12879 tetrads per hermaphrodite flower. Both flower types bear an average of ∼18 ovules. The P/O (pollen/ovule) ratios imply facultative or obligate xenogamy, but hand pollinations show that Lactoris is self-compatible. No floral visitors were ever observed, but stigmata of open-pollinated flowers bore tetrads, and 64% of such styles had pollen tubes. Flowers enclosed in large mesh (1 mm) bags bore similar numbers of tetrads and pollen tubes. Thus, we conclude that Lactoris is anemophilous, a syndrome perhaps reflected by the P/O ratio. Low genetic diversity (isozymes and DNA) supports selfing and implies limited distance wind pollen dispersal. The small size of the island, the ± 1000 extant Lactoris plants, coupled with anemophily, self-compatibility, and pendant flower position, have yielded a geitonogamous system with high seed set and low genetic diversity. If inbreeding depression is expressed, it is in seed germination and seedling vigor, for Lactoris is very difficult to cultivate. For this species, effective conservation practices need to focus on habitat preservation and promotion of outcrossing.     

Pollen Production in the Androdioecious Datisca glomerata (Datiscaceae): Implications for Breeding System Equilibrium

Abstract Androdioecy (the presence of males and hermaphrodites in a breeding population) is a rare reproductive system in plants, with Datisca glomerata (Datiscaceae) representing the only well-documented example. Recent reports of high outcrossing rates, inbreeding depression, and high male pollen production satisfy theoretical predictions for the continued maintenance of androdioecy in populations of this species. However, in prior studies pollen production was measured indirectly in terms of numbers of anthers per flower—based on the assumption that male and hermaphroditic plant have equal numbers of flowers and that anthers from the two sexual morphs produce equivalent amounts of pollen. Herein, we demonstrate that male and hermaphrodite plants do not differ significantly in terms of flower number, but that pollen production in anthers from hermaphroditic plants is 12.6% higher than in anthers from male plants, thus refining the estimate of relative pollen fecundity of male versus hermaphrodite plants. The differential lowers the frequency of males predicted by theory, but is still consistent with the maintenance of androdioecy in this species.     

Intra‐specific pollen polymorphism in Mimosa pigra (Mimosaceae)

Five different types of pollen tetrads were detected from the short and long stamens of the male and hermaphrodite flowers of the androdioecious species, Mimosa pigra L. Light (LM) and scanning electron microscopes (SEM) were used in this study to redescribe the pollen forms and to identify the various pollen types encountered. An identification key and relative percentages of these pollen types were also presented. The study showed that the long stamens of the male flowers and those of the hermaphrodite ones have five (I, II, III, IV and V) and two (I and V) pollen types respectively, whereas the short stamens of both male and hermaphrodite flowers have only one pollen type (type I). We report here the first incidence of intra‐specific pollen polymorphism in androdioecious species.     

Andromonoecy in an Old World Papilionoid legume,Erophaca baetica

Andromonoecy (i.e. the occurrence on individual plants of hermaphroditic and male flowers) is a rare sexual system among the angiosperms, regarded by some authors as a transitional stage from hermaphroditism to monoecy. Having discovered the occurrence of andromonoecy in Erophaca baetica (a Mediterranean shrubby legume with two subspecies), a novelty for Old World papilionoid legumes, we investigated the morpho‐functional correlates and the geographical distribution of this phenomenon in the species. The relative frequencies of hermaphrodite and male flowers were determined in two field and 111 herbarium populations. Biomass allocation within flowers, pollen production and viability, pollen tube growth, nectar production and the temporal pattern of male flower production were also studied in two nearby southern Spanish populations. Virtually all of the studied populations were andromonoecious. Male flowers tended to appear at apical positions within the inflorescence, and became more abundant by the end of the flowering season. Male flowers were externally similar to hermaphroditic flowers (although with less biomass and smaller parts) and released equivalent amounts of pollen and nectar; however, their pollen germinated significantly better. Erophaca is the first example of an andromonecious Papilionoid in the Old World. Since the main difference among floral morphs in this species is functional (i.e. pollen germination rate) rather than morphological, andromonoecy is not readily noticeable, and very careful inspection may be required to reveal it. The potential effect of andromonoecy in enhancing outcrossing rate in this species is discussed.     

中国北亚热带油橄榄(城固32)开花生物学特性研究

为研究北亚热带内陆地区油橄榄（Olea europaea L.）开花物候、开花样式及花器官特征,探讨其有性繁殖系统的特点。试验对西秦岭南坡地区油橄榄（城固32）的开花生物学进行研究,统计开花进程,雄花和两性花在花序上的着生位置和数量,测定雄花和两性花形态指标并切片观察,电镜扫描分析雄花与两性花花粉粒。结果表明：（1）在北亚热带北缘内陆气候条件下油橄榄花期集中在5月,单株花期15~20 d,盛花期持续4~6 d;（2）油橄榄具有雄全同株的性系统且花器官较小,雄花及两性花都具有正常发育的雄蕊。通过制作石蜡切片观察,发现两性花的雌蕊正常发育,而雄花只有较小的子房和败育的柱头;（3）雌蕊是两种花型花器官生物量差异的主要部位,两性花雌蕊的生物量明显比雄花大（P<0.01）,树体分化出雄花投入的资源更少;（4）雄花与两性花在花粉量、花粉粒大小上差异不显著,在着生位置上,花序轴顶花全部为两性花,雄花出现在花序轴的中部和基部的几率分别是21.13%和30.77%。油橄榄品种城固32具有典型的雄全同株现象,雄花更倾向于在花序上出现的位置在行使它雄性功能方面并无优势可言,而且雄花花粉粒在数量、活力方面也没有优势,但是雄花的出现增加了花粉数量和P/O值,提高了植株的雄性适合度,雄花的出现也降低了两性花落花导致的树体资源浪费,保障其在资源有限的环境中能够繁殖最大化。     

The role of staminate flowers in the breeding system of Olea europaea (Oleaceae): an andromonoecious, wind-pollinated taxon

BACKGROUND AND AIMS: Andromonoecy, as a breeding system, has generated a considerable body of theory in terms of sexual selection, but extended records comparing the performance of pollen grains from staminate versus hermaphrodite flowers are still sparse. The objective in this study was to elucidate the role of staminate flowers in the andromonoecious breeding system of olive (Olea europaea). METHODS: To determine the meaning of staminate flowers, an evaluation was made of resource allocation to, and phenology of, staminate and hermaphrodite flowers in the cultivar 'Mission', and a comparison was made of the male function between both kinds of flowers. KEY RESULTS: Dry weight of hermaphrodite flowers was 19 % greater than dry weight of staminate flowers arising in comparable positions of the panicle. This difference was mainly due to pistil and petal weight; there were no significant differences in stamen weight. There were no significant differences between staminate and hermaphrodite flowers in either amount of pollen per anther, or pollen quality as determined by pollen viability, germinability or ability to fertilize other flowers. There was no significant link between gender and time of anthesis. However, position of the flower within the panicle correlated with time of anthesis and gender. Flowers at the apex and at primary pedicels tended to be hermaphrodite and open earlier, whereas flowers arising in secondary pedicels were mainly staminate and were commonly the last to reach anthesis. CONCLUSIONS: It is proposed that the main advantage provided by production of staminate flowers in olive is to enhance male fitness by increasing pollen output at the whole plant level, although a relict function of attracting pollinators cannot be completely discarded.     

Gender variation in Actinidia deliciosa,the kiwifruit

Summary Flower and fruit characters were measured in ten female, five male and five fruiting male selections of A. deliciosa var deliciosa (A. Chev) Liang and Ferguson. Flowers from female vines had functional pistils, which contained many ovules. Stamens appeared to be fully developed but produced only empty pollen grains. Flowers from male vines had functional stamens that produced high percentages of pollen grains with stainable cytoplasmic contents. Pistils did not contain ovules and were generally small with vestigial styles. Fruiting male vines had both staminate and bisexual flowers. Staminate flowers were similar to those found on strictly male vines. Bisexual flowers produced ovules and stainable pollen. Pistils were smaller than in pistillate flowers. Although the three flower sexes differed in style length, ovary dimensions and ovules per carpel, staminate and bisexual flowers were similar in number of flowers per inflorescence, stamen filament length, pollen stainability, inflorescence rachis length and carpel number, and differed from pistillate flowers in these characters. The three flower sexes had similar sepal and petal numbers. The fruit of fruiting males were considerably smaller than those of females. Low ovule number appears to be the major factor limiting fruit size in the fruiting males studied. Prospects for developing hermaphroditic kiwifruit cultivars through breeding are discussed.     

Pollen limitation and the evolution of androdioecy from dioecy

Androdioecy is an unusual breeding system in which populations consist of separate male and hermaphrodite individuals. The evolution of androdioecy is still poorly understood; however, there is evidence from several androdioecious species that the breeding system may have evolved from dioecy (males and females). This article presents a simple deterministic model showing that androdioecy can evolve from dioecy under a broad range of realistic conditions. For the evolution of androdioecy from dioecy, hermaphrodites must be able to invade the dioecious population. Then, males must be maintained, while females are eliminated. Hermaphrodite invasion is favored when females are pollen limited and hermaphrodites have high overall fertility and are self-fertile. Male maintenance is favored when hermaphrodites resemble females, having high seed production and low pollen fitness, and when the selfing rate is not too high. These conditions were satisfied over a broad and realistic range of parameter values, suggesting that the evolution of androdioecy from dioecy is highly plausible.     

Pollen viability and limitation of seed production in a population of the circumpolar cushion plant, Silene acaulis (Caryophyllaceae)

Pollen viability among genders and limitation of female seed production in a natural trioecious population of the circumpolar cushion plant Silene acaulis was examined. Pollen viability was estimated by an in vitro pollen germination experiment. Both male and hermaphrodite flowers displayed large variation in pollen viability (0–53% in hermaphrodite and 0–54% in male flowers). There was a significant difference between genders in pollen viability: male plants had on average higher pollen viability than hermaphrodite plants. Resource and pollen limitation of seed production was studied by an experiment consisting of three treatments; (I) hand-pollination and removal of all other flowers on the cushion, (II) hand-pollination without removal of other flowers, and (III) open pollination without removal of flowers. Hand-pollination increased seed production, whereas removal of flowers had no effect on seed production. Abortion of pollinated ovules during seed development and seed mass did not differ among treatments. To control for effect of fruit number on seed production, data from naturally pollinated individuals was used. There was a positive correlation between both total number of seeds and fruit number, mean seed number per fruit and fruit number, respectively. These results indicate that seed production of 5. acaulis is mainly limited by pollen availability whereas resource competition between fruits is not important as a limiting factor. The possible role of male quality differences between genders and pollen limitation of seed production for maintenance of trioecious reproductive systems is discussed.     

ANDROMONOECY IN ZIGADENUS PANICULATUS (LILIACEAE): SPATIAL AND TEMPORAL PATTERNS OF SEX ALLOCATION

I describe patterns of sex allocation and gamete packaging in the andromonoecious lily Zigadenus paniculatus. In this species, pistil length was continuously, but bimodally, distributed within plants, and smaller pistils contained fewer mature ovules. In hermaphrodite flowers, ovule number per flower increased with blooming rank in small plants but decreased with blooming rank in large plants. Flowers with pistils less than three-fourths stamen length almost never produced fruits and were classified as males. The pedicel, tepals, stamens, and pistil of hermaphrodite flowers were all heavier than those of males. Hermaphrodite flowers were concentrated on the terminal raceme, males on the lower racemes. In combination with acropetal blooming, this spatial separation of flower types resulted in a seasonal decline in the proportion of open flowers that were hermaphrodite. However, individual flowers were protandrous, so that the population sex ratio, initially strongly male-biased, declined as the season progressed. Hand pollinations showed that plants were self-incompatible. Inflorescence size was positively correlated with bulb size, and plants with large inflorescences had a higher proportion of male flowers. Nutrient supplementation had no effect on inflorescence size, but increased the proportion of hermaphrodite flowers. Nutrient-supplemented plants also began blooming earlier than controls. I discuss these patterns in relation to the adaptive significance of andromonoecious breeding systems.     

Pollen and Resource Limitation in Veratrum nigrum L. （Liliaceae）, an Andromonoecious Herb

Pollen limitation and resource limitation were invoked to account for the pattern that flowering plants produce more flowers and ovules than fruits and seeds. This study aimed to determine their relative importance in Veratrum nigrum, a self-compatible, perennial, andromonoecious herb. In order to determine whether female production was limited by pollen grains on stigmas or by available resources, we performed supplemental hand pollination in three populations, male-flower-bud removal in three other populations, and emasculation of hermaphroditic flowers in still another population, resulting in a total of seven populations experimentally manipulated. Across the three populations, supplemental hand pollination did not significantly increase fruit set, seed number per fruit, and total seed production per individual, nor did emasculation of hermaphroditic flowers. Taken together, our results suggest that pollen grains deposited on stigmas were abundant enough to fertilize all the ovules. Male-flower-bud removal significantly increased the mean size of hermaphroditic flowers in all three populations. Female reproductive success was increased in one population, but not in the other two populations possibly due to heavy flower/seed predation. We concluded that the female reproductive success of V. nigrum was not limited by pollen grains but by available resources, which is consistent with Bateman＇s principle. Furthermore, the female reproduction increase of male-flower-bud removal individuals might suggest a trade-off between male and female sexual functions.     

Functional androdioecy in the rare endemic tree Tapiscia sinensis

Tapiscia sinensis, a rare endemic woody plant with both male and hermaphrodite individuals, is distributed in southern China. Whether T. sinensis is functionally androdioecious is unknown. In this study, we compare the male fitness between male and hermaphrodite individuals and perform pollination experiments in different habitats, identify the ability of actual siring of pollen from hermaphrodites and males under natural pollination, and discuss the evolution and maintenance of androdioecy in T. sinensis. Research suggests that flowers and fruits grow synchronously on hermaphrodite plants of T. sinensis from April to June. The males of T. sinensis had more than twice the genetic contribution of hermaphrodites through their male function and the fruit set from male pollination and cross‐pollination was the highest in all of the treatments, whereas that from self‐pollination was the lowest. Additionally, paternity analysis showed that the hermaphroditic pollen could result in siring success under natural pollination. The results showed that T. sinensis is a functionally androdioecious tree, that male individuals might evolve from a hermaphroditic ancestor and that the synchronous growth of flowers and fruit in hermaphrodites might facilitate the evolution and maintenance of androdioecy in T. sinensis.     

Gender polymorphism in flowers of Silene vulgaris (Moench) Garcke (Caryophyllaceae)

Silene vulgaris occurs in Israel as a stolonifcrous tetraploid which forms mostly sexually polymorphic populations. Fully hermaphrodite and fully male-sterile plants are linked by a range of intermediate forms which are gynomonoecious and bear hermaphrodite, male-sterile, and partially male-sterile flowers. Male-sterile flowers differ from hermaphrodite ones by having a narrower calyx, a shorter corolla, a thicker style, and a considerably larger stigmatic area with longer papillae which are more markedly bulbous basally. In individual anthers of hermaphrodite flowers, diameters of stained pollen grains showed a continuous variation from 36 to 80 μm with a modal value of 56. About 30% of pollen was found to be non-stainable. Reduction in male fertility occurs at different levels, from small or inviable pollen grains through abortion of single anthers, abortion of entire androecia, and through different degrees of gynomonoecy to totally male-sterile individuals. The proportion of stainable pollen to ovules in hermaphrodite flowers alone was found to be less than 100. From the data presented, less than a third of all ovules produced in the different kinds of flower develop into seeds. This may reflect an inadequacy of pollen, which the local population of S. vulgaris can tolerate because of its stoloniferous habit.