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Patterns of jack pine (Pinus banksiana Lambert) pollen cone production are of interest because they may help explain jack pine budworm (Choristoneura pinus pinus Freeman) outbreak patterns. We used generalized linear mixed models to analyze pollen cone production in 180 permanent plots in Ontario, Canada between 1992 and 2008. Pollen cone production increased with stand age, and large trees in sparsely-populated stands produced more pollen cones. Defoliation decreased the propensity of trees to produce pollen cones for at least two years. We also identified important patterns that are not explained by defoliation and stand characteristics. Pollen cone production is spatially synchronized among years, trees in central Ontario produced more pollen cones than trees in northwestern Ontario, and background cone production increased over time in the central region but not in more northwestern plots. Synchronized reproduction is common among tree species, but has not previously been noted for jack pine pollen cones. Increasing cone production in central Ontario may be evidence of changing forest and (or) climatic conditions and deserves further investigation. Our model can be used to quantitatively predict pollen cone production and assess the risk of jack pine budworm defoliation. Key words: Choristoneura pinus pinus, Pinus banksiana, population dynamics, spatial synchrony, insect plant interactions. Resume: Les profils de production de cones males chez le pin gris (Pinus banksiana Lambert) presentent un interet parce qu'ils pourraient contribuer a expliquer le comportement des epidemies de tordeuse du pin gris (Choristoneura pinus pinus Freeman). Nous avons utilise des modeles lineaires mixtes generalises pour analyser la production de cones males dans 180 placettes permanentes en Ontario, au Canada, entre 1992 et 2008. La production de cones males augmentait avec l'age du peuplement et les gros arbres dans les peuplements clairsemes produisaient plus de cones males. La defoliation reduisait la propension des arbres a produire des cones males pendant au moins deux ans. Nous avons aussi identifie des profils importants qui ne sont pas expliques par la defoliation ni par les caracteristiques du peuplement. La production de cones males est spatialement synchronisee d'une annee a l'autre: les arbres produisaient plus de cones males dans le centre que dans le nord-ouest de l'Ontario, et la production historique de cones males a augmente avec le temps dans la region centrale mais pas dans les placettes les plus eloignees vers le nord-ouest. La reproduction synchrone est courante parmi les especes d'arbre mais n'avait pas jusqu'ici ete observee chez les cones males du pin gris. La production accrue de cones males dans le centre de l'Ontario pourrait etre un indice que les conditions climatiques et la foret changent et merite d'etre davantage etudiee. Notre modele peut etre utilise pour predire de facon qualitative la production de cones males et evaluer le risque de defoliation par la tordeuse du pin gris. [Traduit par la Redaction] Mots-cles: Choristoneura pinus, Pinus banksiana, dynamique des populations, synchronisme spatial, interactions entre les plantes et les insects., Introduction Many animal populations undergo large, spatially synchronized changes in abundance over time, and determining the causes of these patterns is a central topic in population ecology (Bjornstad and Grenfell [...]

In small, fragmented populations of self-incompatible plant species, genetic drift and increasingly close relationships between plants may restrict the number of genetically different pollen donors, the availability of compatible mates, and the opportunity for pollen competition and selection. These restrictions may reduce the siring success or increase the probability of inbreeding depression in the offspring. To test if this was the case, we hand-pollinated maternal plants in small and large populations of the rare, endemic plant Cochlearia bavarica (Brassicaceae) with pollen from one, three, or nine donors from the same population or with nine donors from a different population. In one additional population of intermediate size, maternal plants were hand-pollinated with ten donors located at a distance of 1, 10, 100, or 1000 m. We then recorded seed and offspring characters. On average, offspring from small populations were smaller than normal and fewer survived to maturity. Increasing the number of pollen donors had a positive effect on reproductive success in small and large populations, but at the highest pollen diversity this occurred at the expense of slightly reduced offspring fitness. Because the total amount of transferred pollen was held constant, these effects could not be attributed to increasing pollen load. Rather, the increasing pollen diversity may have increased the chances of selecting a particularly 'good' donor for fertilization--an example of a sampling effect of diversity. Pollen from outside a population or from 10-100 m away resulted in higher reproductive success and greater offspring size. Effects of population size and pollination treatments on reproductive success and offspring fitness were additive. Apparently, there is no obvious size threshold above which the potential of inbreeding depression can be ignored in C. bavarica. Key words: Brassicaceae; Cochlearia bavarica; endemic plant species; inbreeding depression; Munich, Germany; pollen competition; pollen diversity; pollination distance; population size; sampling effect.

Wind pollination was experimentally demonstrated in Linanthus parviflorus (Polemoniaceae), a predominantly beefly-pollinated, self-incompatible annual. Seed set in plants enclosed in mesh tents that excluded pollinators but allowed airborne pollen flow provided evidence for wind pollination, and the extent of seed set due to wind pollination was compared to that in open-pollinated controls and pollen-supplemented treatments. Additional controls were included to test for possible confounding effects of the mesh tent. Mean seed number in open-pollinated plants was 72.8-81.1% of that in pollen-supplemented plants, while wind pollination alone produced 49.5-52.2%, a smaller but substantial proportion of seed set with pollen supplementation. Further evidence for wind pollination was found in a comparison of sites differing in the extent of wind exposure in two populations of L. parviflorus. Airborne pollen counts were higher in exposed sites than in protected sites, and the difference was marginally significant. Seed set was significantly pollen limited in protected sites, but not in exposed sites. Taken together, the data suggest that wind pollination provides some reproductive assurance in this obligately outcrossing species. Wind pollination is hypothesized to represent an alternative to selfing as an evolutionary solution to the problem of temporal or spatial variation in pollination visitation. Key words: Linanthus parviflorus; Polemoniaceae; pollen limitation; reproductive assurance; self-incompatibility; wind pollination.

The influence of pollen competitive environment on pollen performance (pollen germination, stigmatic penetration, and pollen tube growth rate), the maturation or abortion of initiated fruit, seed size, and seedling vigor was explored by manipulating the size and diversity of stigmatic pollen loads on Mirabilis jalapa. All aspects of pollen performance significantly increased with the number of pollen grains on a stigma or pollen tubes in a style, but was not influenced by the diversity of pollen donors. Plants tended to mature single-ovulate fruits that came from flowers where pollen load size and diversity were greatest and aborted those where these were lowest. No plants from seeds resulting from pollinations with a single pollen grain survived, but other fitness measures were mostly determined by maternal plant. The data suggest that pollen performance is influenced by pollen competitive environment, and both the genetic diversity of the pollen load and number of competing pollen tubes are important determinants of seed/fruit abortion. Key words: competition; fitness; fruit; fruit abortion; maternal effect; Mirabilis jalapa; Nyctaginaceae; pollen.

Differences among flagellated and nonflagellated sperm in land plants are striking, but close examination reveals similarities in pattern of cytoskeleton and in nuclear structure. The microtubular cytoskeleton of flowering plant sperm consists of microtubule bundles arranged obliquely around the nucleus, terminating in cellular extensions. Microtubules are linked into bundles that branch and rejoin along the axis of the sperm cell, forming a cytoskeleton that determines cell shape but does not actively participate in cell movement. Generative cells and sperm share a pattern of microtubules not found in somatic cells. This pattern is initiated in the generative cell, one division before sperm formation, a situation parallel to spermatogenous cell development in vascular plants with flagellated sperm. Chromatin in flagellated and nonflagellated sperm is condensed by specialized histones. Key words: cytoskeleton; generative cell; microtubules; pollen; sperm (plant).

The influence of the sequence of maternal tissue development in Betula pendula upon the potential for male gamete selection was investigated, and the timing of the fixed abortion of one of the two ovules was determined. We used scanning electronic microscopy, confocal laser scanning microscopy, and blue light microscopy. The stigmas remain fresh throughout male anthesis, and may also last after its end, depending on ambient temperatures. The presence of germinated pollen does not induce stigmatic necrotization, and grains may arrive at different times. The pollen tube tips remain within the stigma base until the end of female anthesis. The ovules will not develop until after necrotization of the stigmas. The pollen tubes thus have a fair start to the ovules, regardless of their different arrival times and of the original positions of the pollen grains at the stigma surface. Therefore, competition among different microgametophytes is possible, in spite of low pollination intensity. Our results indicate that when the first pollen tube penetrates an ovule, this ovule starts to outgrow the other one, and even if the other is also penetrated, its vascular support soon atrophies and the megagametophyte will shrivel. Fertilization of both ovules was never seen in this study. Key words: abortion; anemophily; Betula; Betulaceae; brood size; confocal laser scanning microscopy; floral longevity; pollen competition; pollen load.

Effects of ovular secretions on pollen grains were examined in Pseudotsuga menziesii. The exine is cast off in the micropylar canal. A membranelike structure covers parts of pollen grains and appears to protect them. The outer intine consists of fibrous materials, but it also shows a thicker filamentous appearance in some ovules during pollen elongation. The inner intine is electron-dense. Its fibrous nature is occasionally visible. Dissolution of the outer intine varies in amount and manner in ovules from different trees. The plasma membrane near the pollen wall alternatively appears normal and distorted. These different morphologies of the outer intine and of the plasma membrane are considered to result from secretions from the ovule. The outer intine may contain electron-dense globules that are formed in the tube cell and traverse the inner intine. Pollen tube formation appears to be triggered by a secretion from the ovule. Cross-pollinated grains are less distorted compared with self-pollinated grains.

Pollen level effects on fruit size and seed number were investigated in the ground cherry, Physalis longifolia to determine resource and pollen limitation in the plant. Results indicate that large individuals are limited by both pollen and resource levels. These plants allocate resources in a way that maximizes production of seeds. On the other hand, small individuals are limitedonly by pollen levels.

Seed production of a flower depends both on the quantity of pollen received and on its 'quality' as manifested in rates of germination, ovule fertilization, and seed maturation. Disentangling effects of these two factors is complicated by the fact that seed set is a decelerating function of pollen quantity. One potential element of quality is the genetic similarity of pollen donor and recipient. In ten experiments with Delphinium nelsonii, seed set varied with outcrossing distance, a correlate of genetic similarity. Over all experiments, a 10-m distance significantly (P < .02) outperformed shorter and longer distances by 23-33%, suggesting quality f differences. To explore this possibility, we fit decelerating negative-exponential regressions to relationships among stigma pollen load, pollen tube number reaching the ovary, and seed set in a subset of experiments having 1-, 10-, and 100-m treatments. Regression parameters suggested that 10-m pollen is most efficient at producing tubes and seeds, and analysis of residuals from pooled regressions (a nonlinear ANCOVA) showed that 10-m residuals were most positive. The latter effect was significant for pollen load-seed set relationships (P = .009, five experimental replicates) and pollen tube-seed set relationships (P = .021, two replicates), but not pollen load-pollen tube relationships (P = .128, three replicates). These results illustrate the utility of nonlinear regression in distinguishing pollen quantity and quality. They reinforce the conclusion that outcrossing distance affects pollen quality in D. nelsonii, and that an 'optimal outcrossing distance' between 1 and 100 m maximizes seed set on average in pollinations using one donor per carpel. Insofar as quality differences persist in natural pollen mixtures that arrive on stigmas, outcrossing distance should affect reproductive success through both paternal and maternal sexual functions.

Influence of Environmental Quality on Pollen Competitive Ability in Wild Radish ENVIRONMENTAL EFFECTS ON FEMALE reproductive success in plants are well documented [1]. Environmental conditions can also affect pollen characters [...]

A deterministic model was used to determine that limiting values of genotype class frequencies in autotetraploids do not reduce pollen wastage, unlike diploid gametophytic self-incompatibility systems.