Microsporogenesis and male gametogenesis of Jatropha curcas L. (Euphorbiaceae) was studied in order to provide additional data on this poorly studied family. Male flowers of J. curcas have ten stamens, which each bear four microsporangia. The development of the anther wall is of the dicotyledonous type, and is composed of an epidermis, endothecium, middle layer(s) and glandular tapetum. The cytokinesis following meiosis is simultaneous, producing tetrahedral tetrads. Mature pollen grains are two-celled at anthesis, with a spindle shaped generative cell. A few abnormal microspores were observed following the early stages of microgametophyte development.

A method to significantly improve the germination and development of plantlets of Aplectrum hyemale was developed. Seeds of this terrestrial orchid were collected in a natural stand, surface disinfected and grown in vitro on a gellified growth medium in absence of symbiotic fungi. Seeds were sowed whole or after excision of the seed coat. Embryos that were removed from the seed coat showed a significant increase in germination and survival percentages compared to whole seeds. Embryos grew to form a ramified protocorm, irrespective of seed treatment, followed by plantlet formation. Plantlets were successfully acclimatized and transferred to soil conditions. Asymbiotic in vitro culture is therefore shown as a potential tool to produce viable plantlets for use in natural site restoration.

Gynodioecy is a dimorphic breeding system in which male-sterile individuals (i.e., females) coexist with hermaphroditic individuals in populations. Previous studies of two species of Lobelia in North America have documented gynodioecy in parts of their ranges and here, we document gynodioecy for a single population of L. siphilitica and in two populations of L. spicata from western Massachusetts. Our objectives were to (1) determine sex ratios in natural populations of these species, (2) use controlled pollinations to investigate the capacity and extent of self fertilization in hermaphrodites and (3) compare the relative fertility and magnitude of sexual dimorphism in floral morphology between females and hermaphrodites. The frequency of females was only 3% in L. siphilitica, whereas both populations of L. spicata contained 12% females. Hermaphrodites in both species were self-compatible and estimates of mating system parameters confirmed mixed mating in L. spicata. Females of L. spicata had higher fruit and seed production compared to hermaphrodites and there was significant floral size dimorphism. In contrast, there was no sexual dimorphism and no differences in fruit and seed set between females and hermaphrodites in L. siphilitica. We also used herbarium records to document that flowering of these two congeners is well separated temporally in the Northeast and that northeastern collections of L. spicata, but not L. siphilitica, flower significantly later in the season compared to herbarium specimens collected from outside this region. Further, herbarium collections were used to test previous hypotheses concerning the validity of infrageneric classifications in Lobelia spicata; specifically, we confirmed that L. spicata var. campanulata is a male-sterile form of this species.

Rudbeckia fulgida var. sullivantii (Sullivant's Coneflower) is a target species for conservation and restoration at the Midewin National Tallgrass Prairie in Will County, northeastern Illinois, due to its classification as a Regional Forester's Sensitive Species by the United States Forest Service (USFS; i.e., a species for which population viability is a concern because of a significant current or predicted downward trend in population numbers/density or in habitat capability that would reduce a species' existing distribution). We collected data on the reproductive ecology of this species including its breeding system, seed set, and flower visitors at seven populations in northeastern Illinois from 2002–2004, to support a conservation plan for the species on USFS lands. We found that R. fulgida var. sullivantii is mostly self-incompatible. Percent seed set ranged from 26.1 to 69.5 with the great majority of populations having over 45 percent seed set. Insects from 32 families were identified as flower visitors to R. fulgida var. sullivantii. Six out of seven populations had between 18–22 insect families and one population had 11 insect families as flower visitors. We concluded that the reproductive ecology of Rudbeckia fulgida var. sullivantii is not the leading cause for its decline in northeastern Illinois.

Platanthera hookeri (Torr.) Lindl. is a little-studied and increasingly rare species of the Great Lakes–St. Lawrence and Acadian Forest Regions. Long-term studies are essential to provide an understanding of its population and flowering dynamics. Three representative populations, with a total of 54 plants, were monitored in Gatineau Park for up to 25 years (1981–2005). Six life stages were identified: seed/protocorm, juvenile, immature, flowering, vegetative and terminal. This paper deals with the juvenile stage, represented by a total of 16 transient plants, and 38 mature plants in the latter three stages. In the two larger populations, mature plant counts remained constant and most mature plants flowered almost annually for a period of years. Subsequently, the counts declined steadily and most plants flowered every other year. The third population experienced a continuous slow decline. The percentage of plants flowering in the longest-studied population was correlated positively with the total rainfall, and negatively with the mean temperature, of the June–July period of the preceding year. These three populations showed differences in behavior that probably were based on differences in age and habitat. Possible causes of mortality include forest succession, herbivory by White-tailed Deer (Odocoileus virginianus) and acid rain.

Two populations of the clonal orchid Goodyera pubescens (Willd.) R. Br. were studied between 1976 and 2006 in Gatineau Park, Quebec, at the northern edge of the distribution. The species is ranked as “imperiled” in the province. Four life-history stages were identified: seed, juvenile/immature, flowering and vegetative. The populations, which were 5 km apart, expanded with doubling times of 7.5 and 15.9 years, the difference in doubling times being attributed to ongoing herbivory at the latter site. Inter-generational times for vegetative reproduction were 4–8 years, while none of the few juvenile/immature individuals monitored had flowered after 9 years. Large flowerings, of up to 30% of the rosettes in a patch, usually were spaced at intervals of 2–4 years. These large flowerings were synchronous within patches, among patches, and between populations. They occurred in the years that followed years with an extensive warm, dry period in May.

Allometric equations and biomass allocation were determined for the aboveground wood, branch, twig, and leaf components of the invasive tree Acacia auriculiformis in south Florida prior to and after a major hurricane event. A destructive harvest was used and plant partitioned biomass was quantified for 35 trees prior to landfall of hurricane Wilma (October 2005), followed by an assessment of 29 hurricane impacted trees (representing all ontogeny classes) three months later. Allometric equations were developed to estimate plant partitioned biomass using diameter at base and diameter at breast height as predictors of biomass components, leaf area, leaf area ratio, and leaf weight ratio. Diameter at base was the best predictor of biomass allocation in all regression analyses. Hurricane force winds did not alter biomass of major woody components; however significant losses were observed in twig biomass and all measured leaf parameters. The replacement of damaged foliage resulted in overcompensation of leaf area and leaf area ratio. Similarly, leaf biomass, and leaf weight ratio also increased following the hurricane, but levels were lower than pre-hurricane observations. This research facilitates the prediction of A. auriculiformis biomass using non destructive sampling protocols while quantifying its resiliency and compensatory abilities following hurricane disturbance.

Three dominant legume species (Tephrosia virginiana (L.) Pers., Rhynchosia reniformis DC., and Centrosema virginianum (L.) Benth.) found in frequently burned longleaf pine woodlands were grown in a garden plot and treated with a factorial arrangement of shade treatments (±) and burning (±) treatments. Nitrogen fixation was measured using ¹⁵N Isotope dilution method with whole plant recovery (including root systems). Burning treatments decreased total biomass (P < 0.001) and increased root to shoot ratios (P < 0.001). N₂-fixation rates were generally reduced by burning, but there was a complex interaction among species, shade, and burn treatments. For Tephrosia, contrasts of shade (F_1,42 4.48, P < 0.05) and burn (F_1,42 4.42, P < 0.05) indicate that both main treatment effects significantly reduced N₂-fixation rates. Relative to all other treatment combinations, Rhynchosia had elevated levels of N₂-fixation under the no shade by burn treatment. Centrosema showed no effect of shade on N₂-fixation (F_1,42 1.65, P > 0.05), but burns significantly lowered N₂-fixation rates for both shaded and unshaded plants (F_1,42 19.31, P < 0.001). Despite the diverse response of species N₂-fixation activity to treatments, a regression of all individuals regardless of species shows a curvilinear relationship of % N derived from the atmosphere to total plant biomass. The diverse response of these herbaceous legumes to light and fire challenges the conventional wisdom that legumes maintain functional redundancy as a guild across environmental gradients within longleaf pine woodlands.

Urban forests represent patches of biodiversity within otherwise degraded landscapes, yet these forests are threatened by invasion by exotic plant species. We investigated the response of a forest understory to removal of four common exotic species: Elaeagnus umbellata Thunb., Lonicera japonica Thunb., Ligustrum sinense, Laur., and Microstegium vimineum (Trin.) A. Camus in a forest within the city of Raleigh, NC, USA. In the summer of 2001, we initiated a removal experiment with three treatments. In the “repeated removal” treatment, all understory vegetation was initially removed by clipping and new exotic seedlings were repeatedly removed every 2 weeks throughout the study period. The “initial removal” treatment involved a one-time understory vegetation removal with no further weeding. Control plots had no intervention throughout the study period. We conducted vegetation surveys of the plots prior to treatment initiation and in April and August of 2002 and 2003. With a non-metric multidimensional scaling (NMS) ordination, we were able to discern differences in species composition between the repeated removal treatment and the other two treatments. However, using repeated measures ANOVA, we found no significant differences in native species richness, cover, and abundance among treatments during most sampling periods. We also used a seedbank study to determine that while some early successional species were present, no native shrubs and few native trees emerged from the seedbank. These results suggest that (1) repeated removal is required to decrease the importance of exotic species, especially if the site is in close proximity to a source of exotic propagules; and (2) subsequent to exotic removal, native species may not recover sufficiently without supplemental plantings. Therefore, restoration plans for urban forests should incorporate both long-term monitoring and native plant re-introduction to achieve a diverse native community.

Rhamnus cathartica L. is a large shrub or small tree native throughout much of Europe and eastern Asia, but invasive in North America. In this review, the current native and invasive distributions of R. cathartica are documented and possible factors limiting its naturalized distribution are considered. Within its broad distribution, R. cathartica occurs in diverse habitats ranging from urban forests to fens. Rhamnus cathartica is shade tolerant, prefers disturbed areas with moist, but not saturated, soils and may have an affinity for alkaline soils high in calcium carbonate.