Roles of species-preferential seed dispersal by ants and endozoochory in Melampyrum (Orobanchaceae)

Aims Melampyrum pratense and M. subalpinum are two myrmecochorous species, which possess similar habitat requirements and frequently occur together. Despite this, their population sizes differ markedly. Melampyrum pratense populations are usually very large, whereas M. subalpinum has rather small and isolated populations. We suggest that such an imbalance might be partially influenced by the difference in ant-mediated seed-removal rates. Genus Melampyrum is considered to be exclusively myrmecochorous, though to achieve the recent distribution of some Melampyrum species during the Holocene myrmecochory would be highly insufficient. We suggest that endozoochory takes place in the long-distance migration, whereas myrmecochory is important for the removal of seeds on a local scale.Methods For seed-preference analysis, M. pratense and M. subalpinum mixed seed samples were placed around Formica polyctena anthills. After a period of time, the remaining seeds of both species were counted for each sample. The results were analysed by analysis of variance and generalized linear mixed-effect model. To test myrmecochorous removal distances, M. pratense seeds were covered with fluorescent dactyloscopic powder and placed in the vicinity of a large ant trail. The area around the starting plot was searched in the dark using UV LED torchlight 7h after the beginning. The distance from the starting plot was measured for each seed found. Birds, rodents, leporine and a ruminant were fed with M. pratense seeds and fresh plants to test the possibility of endozoochorous dispersal of the species. Animal droppings were searched for intact seeds.Important findings Our field studies show that from mixed seed samples, containing both species, ants significantly preferred the seeds of M. pratense. This may be one of factors that has positive influence on M. pratense success in seed dispersal on mixed stands and consequently in the colonization of favourable sites. Experiments focusing on ant-mediated dispersal distance revealed that F. polyctena ants are able to move seeds over a distance of 36 m in only 7h. This distance is among the furthest known myrmecochorous removals of forest plant seeds. A new Melampyrum seed disperser Oligolophus tridens (Opiliones) was observed repeatedly. Our pilot study documented that Melampyrum seeds are able to pass through the digestive tract of a cow intact. This suggests that large ruminants such as deer, bison or forest-grazing livestock may function as important long-distance dispersers of Melampyrum species.     

Causes of Fruit Set Variation in Polygonatum odoratum (Liliaceae)

Abstract: In Polygonatum odoratum (Liliaceae), flowers located distally within the flowering shoot typically exhibit lower fruit set than flowers located proximally. In this study, experiments were performed to investigate whether the lower fruit set of distal flowers is due to pollen limitation, resource competition or "architectural" effects. We found that (1) fruit set and mean number of ovules per flower decline within the flowering shoot from proximal to distal position; (2) variations in the amount of pollen received do not explain the observed differences in fruit set; (3) the fruit set of the most distal flowers was significantly increased by removal of other flower buds in the flowering shoot just before flower opening, indicating that fruit set in these flowers is resource-limited; and (4) removal of proximal flowers increased the fruit set of later flowers to levels similar to those of early flowers of control shoots, arguing against the architectural effects hypothesis.     

Factors constraining fruit set in Mandevilla pentlandiana (Apocynaceae)

The reproductive success of Mandevilla pentlandiana was studied to disclose its reproductive strategy, and to determine the links between nectar production, breeding system, fruit set and inflorescence size. The plant produces many inflorescences with a large number of flowers but initiates few fruits (9%). This vine is self-compatible but not autogamous. Given that no significant differences could be detected considering many traits (ripe and abortive fruit sets, fruit quality, and seedling survival) between the pollination treatments (self-, cross-and natural-), the low natural fruit set was not related to pollen limitation. Fruits were not distributed at random within inflorescences (earlier fruits had the highest probability of maturation) but there were no significant differences in fruit quality according to different fruit positions. Conversely, the time of fruit initiation influenced most of the fruit-traits. Many developing fruits were aborted (20%). An increase in the probability of abortion was detected when the whole inflorescence was hand pollinated. In addition, a positive correlation was detected between the abortions and the number of ripe fruits which developed before them. Looking at our data from an evolutionary perspective, we argue that a theoretical inflorescence size, corresponding to the intersection point between the mean values of fruit number and fruit set per inflorescence, can be assumed to indicate the optimum inflorescence size that maximizes equally both female and male functions. Comparison between the theoretical and the observed mean inflorescence size suggests, that for M. pentlandiana , pollen donation may be the primary evolutionary factor behind excess flowers.     

Proximate Limitations to Fruit and Seed Set in Phellodendron amurense var. sachalinense

Abstract Fruit and seed set in a dioecious tree, Phellodendron amurense var. sachalinense grown in isolation, were studied for three years in Hokkaido, northern Japan. Hand pollination did not affect fruit set during the three years, but did affect seed-set by increasing the proportion of fruits with higher seed numbers. Artificial defoliation resulted in decreased mean seed mass, but caused no significant differences in mean seed number per fruit. Total seed mass per infructescence increased with inflorescence size except with artificial defoliation where it reached an upper limit. Although the results of the artificial defoliation treatment indicate that resources are most important for fruit and seed set, it is concluded that fruit and seed set of the tree are not limited by resources, since the number of fruits increased with inflorescence size and an artificial defoliation treatment did not decrease seed-number.     

Differential self‐fertilization rates in response to variation in floral traits within inflorescences of Aquilegia buergeriana var. oxysepala (Ranunculaceae)

To assess variation in the proportion of self‐fertilized seeds among flowers within inflorescences and the relationship between floral traits and the rate of self‐fertilization, the proportion of self‐fertilized seeds among individual flowers was estimated using ten microsatellite markers in self‐compatible plants of Aquilegia buergeriana var. oxysepala. Within‐inflorescence variation in floral traits, such as the duration of the male and female phases, flower size, herkogamy and the number of pollen grains and ovules in two natural populations, were investigated. The first flower in an inflorescence produced more seeds and a higher proportion of self‐fertilized seeds than the second flower. The higher proportion of self‐fertilized seeds in the first flowers was accompanied by a higher number of pollen grains and ovules in the bud stage and the female phase. These results indicate that the high proportion of self‐fertilized seeds in the first flowers in an inflorescence may be due to the high number of remaining pollen grains in the female phase. This suggests that variation in floral traits within inflorescences affects seed quality and quantity among flowers within inflorescences.     

Quantitatively determined self-incompatibility. IV. Pollination and seed set in Borago officinalis

Summary The outcomes of sequential double pollination, mixed double pollination and single pollination are compared. Single pollination leads to lower seed set than double pollination. Systematic differences between female genotypes are shown to be possible. It is also shown that failure to set seed is generally due to pre-zygotic maternal factors.     

Phenotypic gender variation within inflorescences of the protogynous species Helleborus foetidus L. (Ranunculaceae)

In the protogynous species H. foetidus, I investigated if investment in sexual structures and seed set shows any trend with position in the flower-opening sequence. In four-flower inflorescences, stamen number decreased with flower position i.e. was highest for the earliest flower and lowest for the latest flower. Ovule number was significantly higher in the latest flower. Stamen and ovule number did not covary, indicating that there is no structural gender trade-off in this species. Seed set (i.e. percentage of ovules producing seed) did not differ between control plants and pollen-supplemented plants and the effect of pollen supplementation did not vary among positions. Seed set showed marginally significant differences between control plants and simulated-herbivory plants, but the effects of this treatment varied significantly among positions. Significant among-position variation in seed set was observed in the control plants but not the simulated-herbivory plants. Seed set of latest-opening flowers of simulated-herbivory plants was significantly higher than that of latest-opening flowers of control plants. H. foetidus support Brunet and Charlesworth's (1995) prediction that in plants with protogynous flowers, later-opening flowers should specialize as female flowers, at least under conditions of high resource availability.     

Relationship between floral longevity and sex allocation among flowers within inflorescences in Aquilegia buergeriana var. oxysepala (Ranunculaceae)

Understanding the fitness of plants with inflorescences requires examining variation in sex allocation among flowers within inflorescences. We examined whether differences in the duration of the male and female phases of flowering lead to variation in sex allocation and reproductive success among flowers within inflorescences. In 2002 and 2003, we quantified floral longevity, floral sex allocation, and reproductive success between the first and the second flowers within inflorescences in a protandrous species, Aquilegia buergeriana var. oxysepala. Floral longevity was greater in the first flowers than in the second ones in both years. The male phase lasted longer, and the initial number of pollen grains and the number of pollen grains removed were greater in the first flowers than in the second ones in both years. Within first flowers, the number of pollen grains removed was greater in flowers that had longer male phases, thus duration of the male phase may positively affect male reproductive success in the first flowers. The female phase lasted longer and the number of ovules was greater in the first flowers than in the second only in 2002. However, seed production per flower and female phase duration in both years were not significantly related. The variation in the number of pollen grains among flowers in this species may be caused by the variation in male phase duration.     

花粉和资源限制对青阳参坐果率的影响

以生长于自然种群的青阳参植株为材料进行补充授粉试验,以人工种植的青阳参植株为材料进行资源限制试验,探讨花粉和资源限制对青阳参坐果率的影响.结果表明:自花授粉、天然授粉和异株异花授粉植株的结实率分别为1.7％、2.25 ％和24％,花粉来源对青阳参坐果存在显著影响;补充施肥和不补充施肥植株的坐果率分别为5.12％和3.1...     

Competition and the compensatory regulation of fruit and seed set in the perennial herb Epilobium dodonaei (Onagraceae)

I studied the effects of competition and soil fertilization on variation of seed yield components of the outcrossing perennial Epilobium dodonaei Vill. using a randomized complete block design. Fertilization as a main effect was not significant. Competition, however, reduced the number of flower buds per shoot (-29%), the number of ovules per fruit (-12%), and the number of ripe fruits per shoot (-51%). In addition, competition caused an increase in abortion of flower buds. Consequently the fruit/flower bud ratio decreased from 0.71 to 0.47. Average seed mass was not reduced significantly by competition. Some of the negative effects of competition on fruit production were mitigated by fertilization. However, competition considerably reduced the proportion of late-aborted seeds, which resulted in an increase of the seed/ovule ratio from 0.31 to 0.49 (+58%). As a consequence of this compensation, the reduction in the number of seeds per shoot due to competition was not significant. At the level of the genet, competition had a strong effect on seed yield due to decreases in the number of shoots produced. I discuss patterns of regulation at consecutive levels of reproduction. Shoots of plants suffering from competition initially invested less in reproductive structures than the control and showed a higher abortion rate of less costly structures early in reproductive development, but also had a lower abortion rate later in their development. The observed compensatory pattern in yield components illustrates the fine-tuning regulation capacity at different levels of reproductive development in plants.     

Distribution and ecology of small cow-wheat (Melampyrum sylvaticum L.; Scrophulariaceae) in the British Isles

Summary

Melampyrum sylvaticum L. is an annual, hemiparasitic herb which mainly grows in light woodland and on upland ledges in northern Britain and Ireland. Its distribution is poorly known due to confusion with the variable M. pratense. A review of its ecology and distribution has been carried out and it has now been recorded from 83 10-km squares in the British Isles, including three in England and two in Wales; an updated distribution map is given. It is probably declining slowly in the lowlands at the margins of its range due to afforestation, development of dense shade, over-grazing and intensive agriculture.     

关于《中国植物志》中鹿药(百合科)花特征的纠正

根据野外调查,同时结合文献分析,指出《中国植物志》和Flora of China中关于百合科(Liliaceae)鹿药花部特征描述存在的问题,并提出修改建议。此外,对其学名进行了简要讨论。     

Influence of pollination systems on fruit set and fruit quality in kiwifruit (Actinidia deliciosa)

Kiwifruit (Actinidia deliciosa (Chev.) Liang and Ferguson) is a dioecious species highly pollination dependent, since fruit size is directly correlated with seed number. To evaluate the best pollination system for this species a study of two natural and two artificial pollination systems was carried out and their effect on fruit set and fruit quality was determined. While anemophilous pollination produced few and small fruits, that were not commercially acceptable, high fruit set percentages and good quality fruits were obtained when insects participated in the pollination process. Artificial pollination, performed as hand pollination, improved yield quantity and quality. When environmental conditions impair insect activity this method can be an useful agricultural practice in order to assure a good yield.     

Variation in fruit set within and among natural populations of the self-incompatible herb Centaurea scabiosa (Asteraceae)

Various factors known to affect fruit set in self-incompatible plants were studied in 11 populations of Centaurea scabiosa . The importance of genetic variation was estimated using isozymes. A low overall genetic differentiation among populations suggested high levels of either current or historical gene flow. Large variation in fruit set was found among populations, among plants within populations, and among flower heads within plants. Most of this variation was explained by differences among flower heads within plants. Within the range in population size studied, there was no indication that plants growing in the smaller populations had lower fruit set than plants in larger ones. A significant positive correlation between genetic variation and population reproductive success was found. Pollinator visitation rate was very high and dominated by bumblebees. It was rendered unlikely that reproduction was limited by pollinator availability. It was even suggested that a very high visitation rate might have negative effects on fruit set in some populations due to an increased proportion of geitonogamous pollination resulting in stigma clogging with non-compatible pollen. The number of flower heads produced by individual plants did not affect fruit set in individual flower heads.     

不同居群准噶尔无叶豆果实和种子特性及种子萌发差异

研究准噶尔无叶豆(Eremosparton songoricum) 6个居群间果实和种子特性及种子萌发差异, 以揭示异质生境下准噶尔无叶豆果实和种子的生态适应机制。结果显示: 居群间准噶尔无叶豆的植株距离(F = 2.34, p = 0.03)和植株冠幅(F = 8.49, p < 0.01)存在显著差异, 沙漠北缘E、F居群和沙漠腹地C居群(受人类干扰剧烈)的植株距离和植株冠幅高于沙漠腹地A、B、D居群; 居群间准噶尔无叶豆果实和种子的长度、宽度、厚度、重量存在显著差异, 居群E、F和C的大部分参数显著高于其他沙漠腹地居群; 居群间果实多子性(F = 6.96, p < 0.01)也存在显著差异, 居群C的果实多子性最高((32.50 ± 4.79)%); 萌发结果表明, 居群间新鲜的成熟种子萌发不存在显著差异, 且萌发率都低于15%; 所有居群的大部分种子都存在物理性休眠现象, 人为划破种皮能显著提高种子萌发率, 但在低温(15/5 ℃)条件下, 所有居群的种子萌发率都较低, 说明低温抑制了种子萌发; 经人为划破种皮解除物理休眠后, 种子的休眠没有完全释放, 居群C、E和F (大种子居群)的种子萌发率显著高于居群A、B和D (小种子居群) (F = 30.77, p < 0.01), 说明准噶尔无叶豆种子不仅存在物理性休眠现象, 也可能存在生理休眠现象。不同程度的种子复合休眠可能是准噶尔无叶豆不同居群适应古尔班通古特沙漠的重要生存策略。     

Factors affecting fruit and seed production in Dactylorhixa maculata (Orchidaceae)

It has been argued that some of resources needed for fruit and seed production in terrestrial orchids originate from storage in underground biomass. Resources for female reproductive traits may also originate from current photosynthesis. Orchid mycorrhiza may also influence fruit and seed production. The extent to which current photosynthetic activity and nutrient uptake via mycorrhizal fungi affect fruit and seed production has only rarely been studied experimentally. This paper examines the importance of photosynthesis and mycorrhiza for fruit and seed production, leaf area and plant status in the next season for Dactylorhiza maculata (L.) Soó in two populations. Plants were hand-pollinated in two populations to assure successful fertilization. Photosynthesis in the main leaves and in the green parts of inflorescence was prevented and/or mycorrhizal function inhibited by applying thiabendazole to plants. None of the treatments affected relative capsule production, but all treatments resulted in significant decreases in capsule dry weight and the number of seeds produced. The fact that seed production remained high in spite of the experimental treatments indicates that resources stored in the underground corms were used in fruit development and seed production. Inhibition of photosynthesis decreased leaf area in the year following treatments, while the other treatments had no effect on subsequent growth.     

Temporal patterns of seed set and decelerating fitness returns on female allocation in Zigadenus paniculatus (Liliaceae), an andromonoecious lily

I describe temporal patterns of seed production in the andromonoecious lily Zigadenus particulatus. Fruit set per flower and seed set per fruit declined through time within plants. Hand pollination experiments showed that this was not due to increasing pollen limitation. Nutrient supplementation had little effect on seed output, but leaf clipping reduced seed production, especially in late-blooming flowers, and removal of early-blooming flowers increased seed set by later flowers. Thus, the temporal pattern of seed output was due to declining availability of photosynthates. Plants with larger bulbs produced larger inflorescences, a greater proportion of hermaphrodite flowers, more fruits per hermaphrodite flower, and more seeds per fruit, but lost a greater fraction of their initial bulb mass as a consequence of fruiting. After controlling for the effects of bulb mass, plants with larger inflorescences produced a greater proportion of male flowers, and plants with more hermaphrodite flowers produced fewer fruits per hermaphrodite flower and fewer seeds per fruit. Thus, the female fitness gain curve was decelerating. The temporal decline in seed output provides a partial explanation for the parallel decline in allocation to pistils. However, a complete explanation for the pattern of gamete packaging requires an understanding of factors controlling male, as well as female, fitness.     

Somatic embryogenesis and plant regeneration from cultured young inflorescences of Oryza sativa L. (rice)

Compact calli initiated from young inflorescences of Oryza sativa L. (rice) on the Linsmaier and Skoog's (LS) medium containing 1 to 2.5mg/l of 2,4-dichlorophen-oxyacetic acid (2,4-D) were used for regeneration studies. After smooth and compact nodules appeared, these calli were transferred to the regeneration medium containing indole-3-acetic acid (IAA) and either kinetin or 6-benzylaminopurine (BAP). Somatic embryos developed in ten days and were examined by histological studies. Some of the embryos showed scutellum-like structures and a coleoptile-coleorhiza bipolar organization. Regenerated plants had the normal chromosome number of 2n=24.     

Effect of ovule position within the pod on the probability of seed production in Bauhinia ungulata (Fabaceae)

BACKGROUND AND AIMS: It has been claimed that ovules linearly ordered within a fruit differ in their probabilities of reaching maturity. This was investigated by studying the effect the position of an ovule within the pod has on seed abortion and seed production in Bauhinia ungulata. METHODS: Fruits collected during the dry seasons of 1999, 2000 and 2001 were opened, and the number, position and status of each ovule within the fruit were recorded. A GLM model was used to assess the effects of population, tree identity and ovule position within the pod on ovule fertilization, seed abortion, seed damage and seed maturation in two populations of B. ungulata. KEY RESULTS: Nearly 30% of the ovules were not fertilized in 1999; this percentage dropped to 5% the following two years. Seed abortion (50%) and seed damage (15%) were the same every year during the study period. Only 15% of the initial ovules developed into mature seeds in 1999; this value increased to 35% in 2000 and 2001. However, seed survivorship was dependent on the position of the ovule within the pod; non-fertilized and early aborted ovules were found more often near the basal end of the ovary. The frequency of seed damage was not affected by position. Mature seeds were found mainly in the stylar half of fruits, where ovules are likely to be fertilized by fast pollen tubes. CONCLUSIONS: The pattern of seed production in B. ungulata is non-random but is dependent upon the position of the ovule within the pod. The results suggest that the seeds produced within a fruit might differ in their vigour.     

Carpology,germination and seedling performance in Digitalis thapsi L. (Scrophulariaceae)

Summary

We analyse the fruiting phase of the life cycleof Digitalis thapsi L. We studied the production and size of seeds and capsules, and the interpopulational variability and inter-relationships of these parameters. The capsule volume, number of seeds per capsule, of seeds per individual, and of capsules per individual were inter-related and fairly affected by the medium, whereas seed weight was found to bea more independent character. A germination study showed that the species has agreat germinative capacity and has positive photoblasty. It is non-dormant especially if incubated under experimental conditions close to the climatic conditions of the site of provenance of the samples. An increase in temperature speeds up the process without increasing germinability. The morphological and biometric characteristics of the first stages of development of the species following germination were analysed. It was found that seed weight is not positively correlated with cotyledon length nor with any of the other parameters con-sidered, and that the length of the fifth leaf is a useful parameter to express inter-populational genetic variability. Seedling production in spring seems to be influenced more by physical than by chemical factors.