Calcium distribution during peltate and capitate glandular trichome development in Lavandula pinnata L. was examined with the potassium antimonate precipitation method. In order to establish a role for calcium in the secretory process and elucidate calcium function in the glands, the effects of calcium removal were investigated by treatment with nifedipine (Nif, a calcium channel blocker) and Ethylene glycol-bis (2-aminoethyl ether)-N, N, N′, N′-tetraacetic acid (EGTA, a calcium chelator). Untreated, mature glands accumulate many calcium precipitates in the subcuticular space and adjacent cell wall during secretion. In Nif or EGTA treated plants these precipitates disappear, and the amount of secretory product is drastically reduced. Calcium removal also results in a reduction in gland density, cells with decreased cytoplasmic density, formation of a lax cell wall, abnormal formation of the subcuticular space, thinning of the cuticle, and the presence of multivesicular bodies near the plasma membrane. At the post-secretory stage, calcium precipitates are common on the degenerating organelles. These results support a role for calcium in gland development, secretion, and programmed cell death.

The absence of WBTs and wood polymorphisms in some species of the Caryophyllales may be related to the particular area of plant analyzed. The present research has the objective of studying the photosynthetic and non-photosynthetic stems of different species and stages of differentiation to register wood polymorphisms and to understand the distribution and occurrence of WBTs. Wood polymorphism was observed in the non-photosynthetic stem of young and adult plants of Opuntioideae and Cactoideae and is also found in the photosynthetic stem of young plants of some species of Cactoideae. Cactoideae present WBT/fibrous dimorphic wood that can be related to cambial variation associated with growth habits and plant development. As expected, in the photosynthetic stem of the adult columnar cacti the wood is monomorphic fibrous in which WBTs were not found. This wood contains a great amount of fibers due to necessity of the mechanical support. In contrast, the globular species do not possess fibers in this area of the stem in either adult or young plants. Opuntia monacantha Haw. had non-fibrous wood in which WBTs were observed in the axial system and in the inner parts of the rays. Fiber clusters were present in the axial system. This wood represents a variation in the wood types described for Opuntioideae. Also, in O. monacantha, cells similar to the WBTs were observed in the pith, which can be interpreted as variation in the morphogenic processes during the ontogeny of the plant, probably a case of homeosis. Monomorphic fibrous wood without WBTs was found along the entire stem of Pereskia bahiensis Gürke. This feature has been observed in other pereskias, and in addition to the others, indicates its proximity to the ancestral cacti.

Mangroves are a diverse group of plants that inhabit tidal zones in the tropics and sub-tropics. Some mangrove species occupy the lower tidal zone in which the substrate is anoxic for long time periods while some mangroves inhabit the upper tidal zone in which the substrate should be less anoxic. Recent research has shown that about 12 species of mangroves from the Americas and from Australia transport air internally from openings in leaves called cork warts, as air enters leaves it collects within leaf aerenchyma (special air spaces within leaves) where the air expands when heated by sunlight. Aerenchyma in leaves is connected to aerenchyma in stems and stilt roots that lead to small roots in the substrate. Eventually, youngest root tissues are aerated while they grow within the anoxic substrate. Data of this study show that cork warts and leaf aerenchyma develop during leaf initiation in both shoot terminals of branches as well as in viviparous seedlings. The number of cork warts per leaf is similar for leaf primordia and for fully enlarged leaves for both Rhizophora species. Tissue sections of leaves of less than 30 mm² area show an area of more translucent cells. Leaves with a surface area of 200 mm² show a distinct aerenchyma tissue in which cells have no contents. For such leaves the depth of aerenchyma was 54 µm with a total leaf depth of 230 µm. Fully enlarged leaves had an aerenchyma depth of about 81 µm while the total leaf thickness was about 660 µm. For all leaves above 30 mm², aerenchyma comprised 25% of total leaf volume. Densities of cork warts were the same for emerging leaf primordia as for fully enlarged leaves. The results of this study show that cork warts and aerenchyma develop in leaf primordia of both terminal buds and viviparous seedlings. Aerenchyma and cork warts become active once they emerge from their stipular coverings.

A revision of Zephyranthes Herbert (Amaryllidaceae) in the Mexican portion of the Yucatán Peninsula Biotic Province is presented. Three species are native in the area, including the newly proposed, Zephyranthes orellanae Carnevali, Duno & J. L. Tapia, which is known from a narrow region of dry forests over rocky soils along the northwestern edge in the Yucatán state. Zephyranthes orellanae is related to Z. citrina Baker but is distinguishable by its narrower leaves. (0.9–1.2 mm wide vs. more that 3 mm in Z. citrina). Zephyranthes chlorosolen (Herb.) D. Dietrich is reported for the first time from the Yucatán Peninsula. The status of Zephyranthes citrina in the Yucatán Peninsula is assessed. The names Cooperia drummondii Herbert ( =  Zephyranthes brazosensis Traub) and Cooperia chlorosolen Herb. ( =  Zephyranthes chlorosolen) are lectotypified. Descriptions of all taxa and a key to their diagnosis are presented, as well as a map and iconography depicting all taxa involved. The conservation status of all three taxa is assessed against IUCN criteria.

We examined vegetation responses to prescribed fire on three mixed-oak sites located in the Blue Ridge Physiographic province of the southern Appalachian Mountains: Alarka Laurel Branch (AL), Robin Branch (RB), and Roach Mill Branch (RM). Each of the study sites was within a sub-watershed that drained a first order stream. Our objectives were to: 1) evaluate overstory mortality following prescribed fire treatments; and 2) assess changes in composition, abundance, and diversity of overstory (stems ≥ 5.0 cm dbh), understory (stems < 5.0 cm dbh, ≥ 0.5 m height), and herbaceous layer (woody stems < 0.5 m height and all herbaceous plants) vegetation in mixed-oak ecosystems. Each site included a burned and unburned area (control). Before the prescribed fire treatments were applied, we established permanent plots (10 × 20 m) in the prescribed burn areas (12 plots in AL, 12 plots in RB, and 10 plots in RM) and adjacent unburned areas (5 plots in AL, 6 plots in RB, and 4 plots in RM), for a total of 49 plots. Within the plots, we sampled vegetation before and after the prescribed burns. All of the prescribed fires were low to moderate intensity; i.e., they had moderate flame temperatures and low flame heights. After the prescribed fires, overstory mortality was low for all sites, and there were no significant differences between mortality in burned areas and that in unburned areas. Understory density was lower on the burned than the unburned plots the first (t  =  −5.26, P < 0.0001) and second (t  =  −3.85, P  =  0.0020) growing seasons after burning. There was either an increase (AL, RB) or no change (RM) in herbaceous layer cover depending on the site and no significant change in species diversity after burning for any site. Thus, we found no negative effects of prescribed fire on herbaceous flora.

We used floristic studies from the state of North Carolina to compare the patterns of total, native and exotic plant species richness from sea level (Atlantic coast) to the summit of the Appalachian Mountains. Few studies have investigated how patterns of native and exotic species richness differ along environmental gradients, and these studies have yielded contrasting results. We compare our results with those few published studies, and demonstrate that there is a need for future studies examining exotic richness along gradients. We modeled the effects of size of study area, year of study, and elevation on species richness using a dataset of sixty-eight floristic studies. Native and exotic species richness showed a positive relationship with area and year. Exotic species showed a steeper slope than native species for the species-area relationship. Richness of both groups was positively but weakly related to year of study. After accounting for area and year, native species displayed a hump-shaped pattern along the elevational gradient. Exotic species richness was weakly related to elevation, which was not a significant variable in the model. This contrasts with the few previous studies that have examined exotic richness patterns along elevational gradients that have found either a strong linear decline, or a strong hump-shaped pattern. Both native and exotic species showed high variation in richness at elevations below 400 m. We conclude that different processes may govern native and exotic plant richness patterns and that exotic richness patterns along gradients may in fact be idiosyncratic due to factors such as disturbance history.

Invasive plant species are often more successful within introduced areas when compared to their natural ranges. Allelopathy has been suggested as a potential mechanism for this success because invasive plants frequently establish monocultures and may produce allelochemicals evolutionarily novel to the recipient community. However, species are typically tested in isolation making the relative strength of allelopathy difficult to assess. We conducted laboratory bioassays for 10 co-occurring non-native species to determine the relative strength of their allelopathic potential. These species represented a suite of successful invaders within a young forest and were from a variety of plant life forms: trees, lianas, shrubs, and herbs. We determined the germination responses of a target species to a gradient of leaf extract concentrations to assess relative allelopathic potential. The relative strength of germination inhibition was quantified by the slope (β) of the germination response to plant extract concentration. Ailanthus altissima extract had the greatest inhibitory effect on target species germination out of all 10 species (β  =  −0.55) while the other tree species, Acer platanoides extract, had small effects on germination (β  =  −0.14). For lianas, Celastrus orbiculatus extract inhibited the target species (β  =  −0.28) more than Lonicera japonica extract (β  =  −0.06). All invasive shrub extracts had very small effects on seed germination (β value −0.03 to −0.19). Extracts of the two herbaceous species, Alliaria petiolata and Microstegium vimineum, had very large inhibitory effects (β  =  −0.37 and −0.38, respectively). In this system, we screened a suite of invasive species for allelopathic potential and determined the relative strength of germination inhibition. Most species, particularly invasive shrubs, did not exhibit sufficient allelopathic potential to suggest allelopathy would occur in the field. Four species, Ailanthus altissima, Alliaria petiolata, C. orbiculatus, and M. vimineum all exhibited strong germination inhibition and warrant additional study in the field.

The distribution of woody plant in wetlands may be influenced by topographic microsites that differ in flooding duration, substrate composition, moisture retention, canopy cover, nutrient availability, and seed trapping ability. In order to assess the effects of microsites on woody plant regeneration in Bonita Swamp, a wetland in Western New York, we conducted an assessment of 15 microsite types, a survey of 400 trees, and a woody seedling count using nineteen 100 m² quadrats in a 4.3 ha study area. Acer × freemanii E.Murr., Fraxinus pennsylvanica Marshall, and Ulmus americana L. dominated the overstory and the often inundated swales occupied 50.3% of the soil surface. Relative to area occupied by each microsite, seedlings were found more often than expected on elevated moss, near elevated moss/soil, near log/root, and swale microsites with 66% of woody seedlings occurring in swales. Acer × freemanii and Fraxinus pennsylvanica occurred more often than expected in the swales. Seedlings appear to prefer moss substrates over soil and wood substrates. Hydrochory may explain the preference of seedlings for “near” microsites onto which wind, water currents and receding spring flood waters deposit floating seeds. Mean percent canopy cover did not vary over the different microsite types, over different species, or between the first and second year (or older) seedlings. Woody seedlings that were two years old or older were found at significantly higher relative elevations and were much less frequent than first year seedlings indicating high mortality and the importance of elevation to survival and establishment. The elevations of microsites are important to woody plant regeneration in this system.

Lianas have the potential to shape forest communities and alter forest regeneration. However, impacts of lianas on forest regeneration, particularly in temperate forests, are largely unstudied. To understand potential liana impacts on the community we need to first know the location and intensity of liana burdens on host trees. We examined liana-tree host preferences within a series of young regenerating deciduous forests in the Piedmont region of New Jersey, USA. Established trees (≥ 5 cm dbh) and the lianas associated with each tree were surveyed in 2008. The five most abundant liana species were Celastrus orbiculatus, Lonicera japonica, Parthenocissus quinquefolia, Toxicodendron radicans, and Vitis species. Host preference for each liana species was measured in two ways, as colonization on tree trunks and coverage in the canopy. Host preferences based on tree species and tree size were compared among liana species. A total of 798 trees were measured and lianas occurred on 64% of them. Host preferences were generally consistent between colonization and canopy expansion, suggesting the same factors that regulate establishment also regulate liana growth. Most liana species had higher colonization and greater canopy cover on early successional trees, particularly Juniperus virginiana. In contrast, Vitis spp. were more abundant on canopy hardwood trees. Slight preferences based on tree size were seen for some species. The preference of lianas for early successional trees may make lianas a contributing factor to the acceleration of succession within this eastern deciduous forest. However, the continued expansion of some lianas at the site, particularly Vitis spp. and C. orbiculatus, may alter future liana-tree associations and forest trajectories.

In order to understand how trees replace themselves during the conversion from agricultural field back into eastern deciduous forest, I first used data sampled in ten old fields over the first 20 years after abandonment to generate six different models of tree replacement. Each of the six models was then used to generate abundance predictions for six common tree taxa (species or genera) from year 21 to 30. Finally each model tested those predictions against the actual data sampled during those same years (21–30) focusing on the predicted rank abundances of the six test tree taxa using Spearman's rank correlation coefficients. I found that: 1) models generally predicted tree abundances and tree replacements well, with the exception of Juniperus virginiana, 2) although some matrix models became constant and some patch models became zero over time, most of the time matrix models had a higher abundance prediction than the patch models for the same species, and 3) among the matrix models, model 3 (which used cover values) had the highest values—especially for the wind-dispersed species—and among patch models, model 4 (which used the number of plots) was often as great or greater than models 5 or 6 (which used stem counts and cover values, respectively)—especially for the bird-dispersed species. Taken together the results suggested that models using cover were closer to the data sampled in the fields compared to the other models within their type (matrix or patch), and that patch models were better estimators of stem densities than matrix models, perhaps due to the inherent dampening properties of matrixes.

This study documented and described a recently located (2003) and significant Piedmont prairie site (Troy Prairie) from Montgomery County, NC. From 2006–08 a complete floristic inventory was conducted. In addition, 75 quadrats (1 × 1 m) were sampled for species frequency, and 12 quadrats were sampled at 3 depths (0–10 cm, 11–20 cm, 21–30 cm) for soil chemistry to determine pH, and extractable P, K, Ca, Mg, Zn, and Mn. A total of 163 vascular plant species were identified, including 62 monocots, 97 dicots, three ferns, and one lycopsid. There were 57 (35%) graminoids and 39 (24%) Asteraceae. Of the Asteraceae, Helianthus schweinitzii (Schweinitz's sunflower) is Federally endangered, while Solidago gracillima and S. radula are both rare-listed for NC. Only five individuals of H. schweinitzii were found in this study of an estimated 100 in 2003. Eighty-seven (53%) species had previously been reported as occurring in prairie-like associations. Andropogon gerardii and Rubus sp. had the highest frequency at 48%. Troy Prairie is one of only three known A. gerardii populations in North or South Carolina > 0.5 ha. The site contains upland to hydric conditions, and 42 (26%) of the species listed were obligate to facultative wetland. The mean soil pH was very strongly acidic (4.9). Phosphorus, K, and Ca levels were low for all three sampled depths for both upland and hydric sections, while there were medium levels of Mg. A portion of the site is under current consideration for a highway improvement project.