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Because the flowering and fruiting phenology of plants is sensitive to environmental cues such as temperature and moisture, climate change is likely to alter community-level patterns of reproductive phenology. Here we report a previously unreported phenomenon: experimental warming advanced flowering and fruiting phenology for species that began to flower before the peak of summer heat but delayed reproduction in species that started flowering after the peak temperature in a tallgrass prairie in North America. The warming-induced divergence of flowering and fruiting toward the two ends of the growing season resulted in a gap in the staggered progression of flowering and fruiting in the community during the middle of the season. A double precipitation treatment did not significantly affect flowering and fruiting phenology. Variation among species in the direction and magnitude of their response to warming caused compression and expansion of the reproductive periods of different species, changed the amount of overlap between the reproductive phases, and created possibilities for an altered selective environment to reshape communities in a future warmed world. climate change | global warming | precipitation

Estimates of the sex ratio and cost of reproduction in plant populations have implications for resource use by animals, reserve design, and mechanisms of species coexistence, but may be biased unless all potentially reproductive individuals are censused over several flowering seasons. To investigate mechanisms maintaining dioecy in tropical forest trees, we recorded the flowering activity, sexual expression, and reproductive effort of all 2209 potentially reproductive individuals within 16 species of Myristicaceae over 4 years on a large forest plot in Amazonian Ecuador. Female trees invested > 10 times more biomass than males in total reproduction. Flowering sex ratios were male-biased in four species in [greater than or equal to] 1 year, and cumulative 4-year sex ratios were male-biased in two species and for the whole family, but different mechanisms were responsible for this in different species. Annual growth rates were equivalent for both sexes, implying that females can compensate for their greater reproductive investment. There was no strict spatial segregation of the sexes, but females were more often associated with specific habitats than males. We conclude that male-biased sex ratios are not manifested uniformly even after exhaustive sampling and that the mechanisms balancing the higher cost of female reproduction are extremely variable. Key words: dioecious; investment; Myristicaceae: reproduction; sex-ratio; tropical forest; Yasuni.

In distylous, self-incompatible plants, clonal propagation, unbalanced floral morpb frequencies, and reduced population size can interfere with the functioning of distyly by compromising legitimate intermorph pollinations, resulting in reduced reproductive output. Here, we examined the mating system and the impact of mate availability, population size, and spatial aggregation of morphs on reproductive output in the distylous, clonal, aquatic plant Hottonia palustris. Controlled pollinations under greenhouse conditions detected no spontaneous selfing without the action of a pollen vector (autonomous autogamy) and demonstrated very low fruit and seed development after self-pollination. Intermorph (legitimate) crossings resulted in high reproductive output in both floral morphs (long- and short-styled individuals), whereas intramorph (illegitimate) crossings decreased fruit and seed development by more than 50%, indicating that the species has partial intramorph-incompatibility. In natural populations, small population size and increasing deviation of floral morph frequencies negatively affected reproductive outcome. Individuals of the majority morph type developed significantly fewer fruit and seeds than individuals of the minority morph type. This rapid decline in fecundity was symmetrical, indicating that regardless of which morph was in the majority, the same patterns of negative frequency-dependent mating occurred. Increasing spatial isolation between compatible morphs significantly reduced fruit and seed set in both morphs similarly. This study provides clear indications of frequency- and context-dependent mating in natural populations of a distylous plant species. Key words: clonal propagation; frequency-dependent selection; heterostyly; Hottonia palustris; legitimate vs. illegitimate pollination; morph bias; pollen dispersal.

The article focuses on the molecular markers and superior phenotypic methods, used to clarify the genetics of apomixis in monocots as well as dicots during the past 15 years.

Abstract: Correlative data from monocots suggest that cytokinin (CK) regulates seed development. The involvement of CKs in seed growth was investigated using pea, a eudicot with an unknown CK profile, [...]

Abstract: Allozyme markers were used to fingerprint clones of the grassland plant Hieracium pilosella L. and, by inference, to estimate the relative importance of sexual and vegetative reproduction in a [...]

The assumption of a ubiquitous trade-off between male and female investment is challenged by arguing that in highly self-fertilizing species, stabilizing natural selection should favor highly efficient ratios of male to female gametes. Further, an artificial selection on pollen and ovule production per flower in two sister species with contrasting mating systems is conducted.

The magnitude of pre- and postzygotic barriers between naturally occurring sympatric populations of Mimulus guttatus and Mimulus nasutus, is estimated. Findings indicate greater potential for introgression from Mimulus nasutus to Mimulus guttatus than for the reverse direction.

Abstract: Field trials established with clones and seedlings from the same families provide an opportunity for comparing full-sib family performance across propagule types. More than 1200 different clones together with [...]

Abstract: We studied flower stimulation in two young miniaturized seed orchards of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) in Oregon. In experiment 1, female and male flowering were substantially [...]

Abstract: The alien invasive vine Vincetoxicum rossicum (Kleopow) Barbar. is problematic in the Lower Great Lakes Basin of North America. The lack of effective control strategies exacerbates the need for [...]

Abstract: The Wallemiomycetes includes three species of molds from the genus Wallemia. These fungi are adapted to environments of high osmotic stress, contaminate various foods, cause respiratory disease, and have [...]

Given the occurrence of mixed mating systems among plants, a general mechanism explaining the evolution and maintenance of this condition is needed. Although numerous theoretical models predict mixed mating to be evolutionarily stable, conditions favoring intermediate selfing are often stringent and have limited applicability. Here we investigated the role of vegetative herbivory, a ubiquitous biotic factor limiting plant reproduction, in the mating system expression of Impatiens capensis (Balsaminaceae), a species with an obligate mixed-mating system (individuals produce both selfing, cleistogamous, and facultatively outcrossing, chasmogamous flowers). Herbivory reduced proportional chasmogamous reproduction partially, but not entirely, through a reduction in plant size and the strength of this effect varied among replicates. Herbivory decreased geitonogamous selfing in chasmogamous flowers via several mechanisms including reduced chasmogamous flower display size and pollinator visitation rate and altered pollinator composition. Overall, herbivory caused a decrease in whole-plant outcrossing, indicating that the effects of herbivory on proportional chasmogamous reproduction, which favor selfing, outweigh the effects on chasmogamous outcrossing rate, which favor outcrossing. Not only do our findings unravel the mechanisms underlying herbivore-mediated changes in the mating system, but they also point to the role of natural enemies in contributing to the maintenance of a mixed mating system. Key words: Impatiens capensis; inbreeding; mating system; outcrossing; plant-pollinator interactions; vegetative herbivory.

Deficiencies in boron, a microelement that is essential for the growth and development of higher plants, often cause problems in reproductive growth. Rhamnogalacturonan-II (RG-II) in cell wall pectin acts as the sole receptor for boron in plant cells, forming a borate cross-linked RG-II dimer (dRG-II-B), but the physiological functions of dRG-II-B remain unknown. We have previously shown that the pectin glucuronyltransferase 1 gene NpGUT1, which is involved in the biosynthesis of RG-II sugar chains, is essential for the formation of the RG-II-B complex, resulting in tight intercellular attachment in meristematic tissues. Because NpGUT1 expression was found to be abundant in reproductive organs in addition to meristematic tissues, we analyzed the expression and functions of NpGUT1 in more detail in tobacco reproductive tissues. Specific NpGUT1 expression was detected in the tapetum of flower buds and in the pollen, pollen tube tips, and transmitting tissue of the pistils of flowers. Dexamethasone-induced expression of the NpGUT1 antisense gene in flower buds resulted in the formation of sterile flowers with aberrant development of pollen and transmitting tissue. Pollen tubes could not pass through pistils with aborted transmitting tissue, and expression of an NpGUT1 antisense gene in germinating pollen inhibited pollen tube elongation, accompanied by the absence of pectin RG-II and boron in the pollen tube tip. These results indicate that expression of NpGUT1 is required for the development and functions of male and female tissues. boron | plant reproduction | NpGUT1

Population context should influence pollination success and selection on floral display in animal-pollinated plants because attraction of pollinators depends not only on the characteristics of individual plants, but also on the attractiveness of co-occurring conspecifics. The insect-pollinated herb Primula farinosa is polymorphic for inflorescence height. Natural populations may include both long-scaped plants, which present their flowers well above the soil surface, and short-scaped plants, with their flowers positioned close to the ground. We experimentally tested whether seed production in short-scaped P. farinosa varied with local morph frequency and surrounding vegetation height. In tall vegetation, short-scaped plants in polymorphic populations produced more fruit and tended to produce more seeds than short-scaped plants did in monomorphic populations. In low vegetation, population composition did not significantly affect fruit and seed output of short-scaped plants. The results suggest that long-scaped plants facilitate short-scaped plants in terms of pollinator attraction and that the facilitation effect is contingent on the height of the surrounding vegetation. The documented facilitation should contribute to the maintenance of the scape length polymorphism in ungrazed areas where litter accumulates and vegetation grows tall. Key words: alternative reproductive strategies; facilitation; floral display; plant height; pollination; positive interactions; predation; Primula farinosa.

The basic tenet of sex allocation theory is that an organism's reproductive success, through either male or female function, can be represented as a sex-specific, monotonic, increasing function of the organism's investment of resources in that function. The shapes of these curves determine what patterns of resource allocation can be evolutionarily stable. Although SA theory has stimulated creative thinking about plant sexual tactics, quantifying the shapes of male and female gain curves has proven so difficult that other approaches must be considered. I contrast sex allocation theory to a different, emerging viewpoint, pollen presentation theory (PPT), which attempts to address variation in reproductive success by measuring and modeling the quantitative fates of pollen grains. Models suggest that RS through male function depends heavily on the packaging and gradual dispensing of pollen to pollinators, even with the amount of investment held constant. Many plants do deploy pollen gradually, through morphological and 'behavioral' mechanisms that range from obvious to subtle. They may thereby influence many aspects of the evolution of sexual modes in plants, including transitions between dioecy and cosexuality. After reviewing the main implications of the models, I discuss recent work aimed at testing some key assumptions and predictions by functional and comparative studies in the genus Penstemon. Species of Penstemon conform to PPT predictions that bee-adapted flowers will restrict per-visit pollen availability more than hummingbird-adapted flowers.

Many invasive species are benign in their native region--are there interactions between their key traits and the new habitats that explain invasion success? The giant perennial herb Heracleum mantegazzianum is a problematic invader in Europe and is also naturalized in North America. We compared its population structure and reproductive behavior in the native (W. Caucasus) and invaded (Czech Republic) areas in managed (pastures) and unmanaged sites. The age structure of the populations and age at flowering were analyzed using herb-chronology, a method based on counting annual rings in the secondary xylem of roots. The species was strictly monocarpic; most plants in unmanaged sites in the invaded range flowered in the third and fourth yr (maximum 12 yr). In unmanaged habitats, plants from the native range flowered later than those from the invaded range. In both ranges, flowering was delayed in managed sites where the population density was higher and most plants flowered around the fifth year. Reproductive output of individual plants was neither related to population density nor to age at flowering. More favorable climatic conditions in the invaded region, together with increased chances for dispersal in a densely colonized central Europe, seemed to allow the massive invasion. Key words: biogeography; Caucasus; Czech Republic; demography; habitat type; Heracleum mantegazzianum; herb-chronology; invasive alien plant.

Based on the general tendency tier females of dioecious plants to pay higher reproductive cost than males, it has been predicted that females should have much more reduced reproductive outputs and diminished vegetative production than males in energy-limited habitats. Nevertheless, this prediction has rarely been directly investigated. We investigated altitudinal changes in reproductive biomass and shoot production, normalized by plant size, for females and males of a shrub willow, Salix reinii, on Mr. Hakkoda, northeast Japan. Females maintained higher reproductive biomass than males at till altitudes; however, reproductive allocation for both sexes tended to decrease at a similar rate with an increase in altitude. Moreover, females vegetatively produced at the same rate as males at all altitudes. These findings suggest that females have a mechanism to compensate for the extra investment in reproduction irrespective of a changing environment. Shoot production did not change with altitude, suggesting that S. reinii gave priority to vegetative investment at the cost of reproductive output at higher altitudes. Inconsistent with general predictions, females did not respond more sensitively than males to severe environmental conditions in either reproductive allocation or shoot production, despite much higher resource investment in reproduction. Key words: altitudinal gradient; annual shoot production: dioecious shrub; Mr. Hakkoda, Japan; reproductive cost; reproductive effort; Salicaceae; Salix reinii.

Abstract: Information on floral resource costs is fundamental for understanding how selection operates on floral morphology. In this study, I explored the cost of maturing flowers in a self-incompatible population [...]

The study examined one potential bias and finds that published studies of outcrossing rates contain far fewer obligate outcrossers than expected. Because this study examines only one potential bias, and finds it to be large, conclusions regarding either the frequency of mixed mating of shape of the distribution of outcrossing rates in nature are premature.

Abstract: The genus Silene is a good model for studying evolution of the sex chromosomes, since it includes species that are hermaphroditic and dioecious, while maintain a basic chromosome number [...]

An experiment that demonstrates short-term changes in trait means, variances, and covariances that happen from the interaction of selection, genetic drift, and mating system is described. Results show that genetic variances and covariances were likely to change rather dramatically over a short period of time if the mating system of a population changes at the same time with selection.

Abstract Introduction Gender-Biased Nectar Production (GBNP) in Dichogamous Plants Commonalities among Dichogamous Plants with GBNP GBNP is Male-Biased as Often as Female-Biased Nectar Production Biases Are Modest in Most Plants [...]

Abstract: Size-dependent reproductive effort is an important component of plant fitness. The responses of reproductive effort to environmental factors in Amaranthus retroflexus L. were measured in two experiments. A wide [...]

The role of inbreeding avoidance in maintaining sexual system variation in Wurmbea biglandulosa was examined. It was found that present sexual system variation in W. Biglandulosa is maintained by high inbreeding depression coupled with differences in selfing rates among monomorphic and dimorphic populations.

Kinds of Plants Plants can: a) grow 90 meters tall from a seed smaller than your thumbnail; b) produce seeds weighing over 9 kilograms; c) have flowers that can be […]

The intensive reconstructive sampling (1957-2004, 39 localities), a systematic direct observation (1992-2004, 1 locality) and particular direct observations (66 localities) of Posidonia oceanica meadows were analysed together with temporal series of flowering available in the literature (19 localities). This allowed the examination of temporal and spatial variability in annual flowering prevalence (FP, the fraction of meadows flowering in a given year) and of annual meadow flowering intensity (FI, number of inflorescences per shoot) for the period 1979-2004 across the Western Mediterranean, as well as spatial variability of flowering frequency (FF, the fraction of years that a given meadow has flowered) and shoot flowering probability (Pf, fraction of flowering stalks appeared per annual segment). Each year, on an average 17% of the investigated meadows flowered, ranging from 3 to 86% of meadows among the years. The highest annual FP and FI values were obtained in 2003 (FP = 0.86 and mean FI = 0.23 [+ or -] 0.03 inflorescences shoo[t.sup.-1]). A secondary peak of FP and mean FI occurred 9 years earlier, in 1994 (FP = 0.44 and mean FI = 0.08 [+ or -] 0.02). Both peaks of flowering occurred after hot summers. Flowering synchrony in particular years across the Western Mediterranean and clines of increased meadow flowering frequency towards the North and East, suggests the existence of large-scale environmental mechanisms controlling the floral induction. On the other hand, meadow FF and Pf were highly heterogeneous among and within the meadows, indicating that local factors also may play a significant role in flowering induction. When flowering, the Western Mediterranean meadows showed an average 0.11 [+ or -] 0.02 inflorescences shoo[t.sup.-1], but FI greatly varied among and along the series (from 0.002 to 0.54 inflorescences shoo[t.sup.-1]) and decreased significantly with depth but was independent of meadow shoot density and meadow latitude or longitude. The shoot flowering probability was quite low (0.007 [+ or -] 0.002 inflorescences shoo[t.sup.-1] [year.sup.-1]) and exponentially increased with shoot age., Introduction Seagrasses are clonal plants for which sexual reproduction is believed to play a modest role, compared to clonal reproduction (Hemminga and Duarte 2000). This is the case for Posidonia [...]

Drought tolerance (DT) and drought avoidance (DA) are two major mechanisms in drought resistance of higher plants. In this study, the genetic bases of DT and DA at reproductive stage in rice were analyzed using a recombinant inbred line population from a cross between an indica lowland and a tropical japonica upland cultivar. The plants were grown individually in PVC pipes and two cycles of drought stress were applied to individual plants with unstressed plants as the control. A total of 21 traits measuring fitness, yield, and the root system were investigated. Little correlation of relative yield traits with potential yield, plant size, and root traits was detected, suggesting that DT and DA were well separated in the experiment. A genetic linkage map consisting of 245 SSR markers was constructed for mapping QTL for these traits. A total of 27 QTL were resolved for 7 traits of relative performance of fitness and yield, 36 QTL for 5 root traits under control, and 38 for 7 root traits under drought stress conditions, suggesting the complexity of the genetic bases of both DT and DA. Only a small portion of QTL for fitness- and yield-related traits overlapped with QTL for root traits, indicating that DT and DA had distinct genetic bases.

We studied the pollination biology of 18 common insect-pollinated plant species on Kent Island, a boreal island in the Bay of Fundy, New Brunswick, Canada. Under natural conditions, fruit set was relatively high in most of the species studied [although it was very low ( Overall, our results demonstrate that for many insect-pollinated plant species on Kent Island, pollinators are likely to be limiting, autogamy is common and inbreeding depression is negligible. Although pollinator limitation and autogamy regularly occur in mainland habitats as well, a review of the literature suggests that they may be more common on islands such as Kent Island. If such island-mainland differences are general, they may arise because genotypes and species capable of self-fertilization are more likely than obligate outcrossers to colonize and become established in isolated habitats.