Howard S. Neufeld

Why some stems are red: cauline anthocyanins shield photosystem II against high light stress

Red-stemmed plants are extremely common, yet the functions of cauline anthocyanins are largely unknown. The possibility that photoabatement by anthocyanins in the periderm reduces the propensity for photoinhibition in cortical chlorenchyma was tested for Cornus stolonifera. Anthocyanins were induced in green stems exposed to full sunlight. PSII quantum yields (ФPSII) and photochemical quenching coefficients were depressed less in red than in green stems, both under a light ramp and after prolonged exposures to saturating white light. These differences were primarily attributable to the attenuation of PAR, especially green/yellow light, by anthocyanins. However, the red internodes also had less chlorophyll and higher carotenoid:chlorophyll ratios than the green, and when the anthocyanic periderm was removed, small differences in the ФPSII of the underlying chlorenchyma were retained. Thus, light screening by cauline anthocyanins is important, but is only part of a set of protective acclimations to high irradiance. Hourly measurements of ФPSII on established trees under natural daylight indicated a possible advantage of red versus green stems under sub-saturating diffuse, but not direct sunlight. To judge the wider applicability of the hypothesis, responses to high light were compared for red and green stems across five further unrelated species. There was a strong, linear, interspecific correlation between photoprotective advantage and anthocyanin concentration differences among red and green internodes. The photoprotective effect appears to be a widespread phenomenon.

Visible foliar injury caused by ozone alters the relationship between SPAD meter readings and chlorophyll concentrations in cutleaf coneflower

The ability of the SPAD-502 chlorophyll meter to quantify chlorophyll amounts in ozone-affected leaves of cutleaf coneflower (Rudbeckia laciniata var. digitata) was assessed in this study. When relatively uninjured leaves were measured (percent leaf area affected by stipple less than 6%), SPAD meter readings were linearly related to total chlorophyll with an adjusted R2 of 0.84. However, when leaves with foliar injury (characterized as a purple to brownish stipple on the upper leaf surface affecting more than 6% of the leaf area) were added, likelihood ratio tests showed that it was no longer possible to use the same equation to obtain chlorophyll estimations for both classes of leaves. Either an equation with a common slope or a common intercept was necessary. We suspect several factors are involved in altering the calibration of the SPAD meter for measuring chlorophyll amounts in visibly ozone-injured leaves, with the most likely being changes in either light absorption or scattering resulting from tissue necrosis.

Ozone injury on cutleaf coneflower (Rudbeckia laciniata) and crown-beard (Verbesina occidentalis) in Great Smoky Mountains National Park

Incidence and severity of visible foliar ozone injury on cutleaf coneflower (Rudbeckia laciniata L.) and crown-beard (Verbesina occidentalis Walt.) were determined along selected trails at three locations in Great Smoky Mountains National Park during the summers of 2000 and 2001: Clingmans Dome, Cherokee Orchard Road and Purchase Knob. Cutleaf coneflower exhibited a greater amount of foliar injury than crown-beard each year of the 2-year study. Incidence and severity of injury was significantly greater for cutleaf coneflower growing near the edge of the Clingmans Dome trail than in the interior of the stand. Injury was greater at Clingmans Dome than Purchase Knob (70% vs. 40% ozone-injured plants, respectively), coincident with greater ozone exposures. In contrast to Clingmans Dome, there were no differences in injury between plants growing near- and off-trail at Purchase Knob. Differences in sensitivity to ozone were not observed for crown-beard growing near the edge compared with the interior of the stand adjacent to the Cherokee Orchard Road Loop. Ozone injury was greatest on the lower leaves for both species sampled with over 95% of the injured leaves occurring on the lower 50% of the plant. This is the first report of foliar ozone injury on these plant species in situ, in the Park, illustrating the great variability in symptom expression with time, and within and between populations.

Interpreting spatial variation in ozone symptoms shown by cutleaf cone flower, Rudbeckia laciniata L.

Visible injury caused by ozone is recorded every year in native plant species growing in Great Smoky Mountains National Park (USA). One of the most sensitive species, cutleaf coneflower (Rudbeckia laciniata L.), shows great variation in symptoms between and within populations but the causes of this variation and its ecological significance are currently unknown. This paper presents data relating to genetic variation, ozone concentrations, stomatal conductance and light (PAR) within populations. The data show that populations differ in genetic diversity, one consisting of only three genets while another was very diverse. In the former population, symptoms varied greatly within a single genet, pointing to a large micro-environmental influence. Measurements of ozone, stomatal conductance and PAR within plant canopies suggest that variation in symptom expression is unlikely to be due to differences in ozone flux and more likely to be due to variation in light. The variation in visible symptoms raises the question of what bioindicators actually indicate, and it suggests that symptoms should be interpreted with great caution until the underlying causes of that variation are fully understood.

A rootbox for quantitative observations on intact entire root systems

A rootbox is described which allows observation of an intact, entire root system. Roots are sandwiched against a plexiglass surface by a nylon mesh that is impermeable to roots, but permeable to water and nutrients. To quantify root growth non-destructively, roots of different size classes are traced onto acetate sheets using different color pens, and root lengths determined by digital image analysis.

Fire in a Thermic Oak-Pine Forest in Linville Gorge Wilderness Area, North Carolina: Importance of the Shrub Layer to Ecosystem Response

ABSTRACT Dedication The authors of this article dedicate this paper to the memory of Dr. Bruce Haines, University of Georgia, in honor of his outstanding accomplishments in the field of ecosystem ecology. A good scientist, a good mentor, and a good friend. In the fall of 2000, a ground fire burned much of the Linville Gorge Wilderness Area, North Carolina, providing an opportunity to study the effects of fire on an oak-pine forest that had not been burned in 50 years. There was no immediate overstory mortality in our study plots. Most aboveground stems of Kalmia latifolia were killed back, but most survived and subsequently re-sprouted. Fire reduced surface organic horizons by nearly 50%, and increased light penetration ∼15%, resulting in greater soil temperature extremes. Fire increased species richness in the herb layer and allowed establishment of pine seedlings and also the exotic invasive tree species Paulownia tomentosa. Rates of soil respiration and litter decomposition were significantly lower in burned plots one year *email address: neufeldhs@appstate.edu post-fire. Changes in the microenvironment in the lower strata following fire were caused primarily by the disappearance of the Kalmia canopy. This temporary loss of the shrub layer appeared to influence composition of the ground layer as well as the re-accumulation of surface soil carbon via reduced litter decay.

Tropospheric ozone assessment report: Global ozone metrics for climate change, human health, and crop/ecosystem research

Assessment of spatial and temporal variation in the impacts of ozone on human health, vegetation, and climate requires appropriate metrics. A key component of the Tropospheric Ozone Assessment Report (TOAR) is the consistent calculation of these metrics at thousands of monitoring sites globally. Investigating temporal trends in these metrics required that the same statistical methods be applied across these ozone monitoring sites. The nonparametric Mann-Kendall test (for significant trends) and the Theil-Sen estimator (for estimating the magnitude of trend) were selected to provide robust methods across all sites. This paper provides the scientific underpinnings necessary to better understand the implications of and rationale for selecting a specific TOAR metric for assessing spatial and temporal variation in ozone for a particular impact. The rationale and underlying research evidence that influence the derivation of specific metrics are given. The form of 25 metrics (4 for model-measurement comparison, 5 for characterization of ozone in the free troposphere, 11 for human health impacts, and 5 for vegetation impacts) are described. Finally, this study categorizes health and vegetation exposure metrics based on the extent to which they are determined only by the highest hourly ozone levels, or by a wider range of values. The magnitude of the metrics is influenced by both the distribution of hourly average ozone concentrations at a site location, and the extent to which a particular metric is determined by relatively low, moderate, and high hourly ozone levels. Hence, for the same ozone time series, changes in the distribution of ozone concentrations can result in different changes in the magnitude and direction of trends for different metrics. Thus, dissimilar conclusions about the effect of changes in the drivers of ozone variability (e.g., precursor emissions) on health and vegetation exposure can result from the selection of different metrics.

Heavy metal concentrations in some non-vascular plants in an Amazonian rainforest

The presence of acid rain in the remote Amazon rainforest of southwestern Venezuela suggests the possibility of long-range transport of industrial pollutants to that region. Heavy metal concentrations were analyzed in samples of bryophytes and epiphyllous organisms growing on leaves and on bark in this forest. Concentrations of Cd, Pb, Ni, and Cr were higher in leaves with epiphylls than in leaves without epiphylls. All heavy metal concentrations in bryophytes from the Amazon basin site were lower than in bryophytes from temperature zones. The results indicate that long-range transport of air pollutants from industrial centers to the remote Amazon basin is occurring at only extremely low rates. Heavy metal concentrations in bryophytes and epiphylls at this site may still be considered close to present day background levels.

Spermine inhibits Vibrio cholerae biofilm formation through the NspS-MbaA polyamine signaling system

The aquatic bacterium and human intestinal pathogen, Vibrio cholerae, senses and responds to a variety of environment-specific cues to regulate biofilm formation. Specifically, the polyamines norspermidine and spermidine enhance and repress V. cholerae biofilm formation, respectively. These effects are relevant for understanding V. cholerae pathogenicity and are mediated through the periplasmic binding protein NspS and the transmembrane bis-(3′-5′) cyclic diguanosine monophosphate (c-di-GMP) phosphodiesterase MbaA. However, the levels of spermidine required to inhibit biofilm formation through this pathway are unlikely to be encountered by V. cholerae in aquatic reservoirs or within the human host during infection. We therefore hypothesized that other polyamines in the gastrointestinal tract may control V. cholerae biofilm formation at physiological levels. The tetramine spermine has been reported to be present at nearly 50 μm concentrations in the intestinal lumen. Here, we report that spermine acts as an exogenous cue that inhibits V. cholerae biofilm formation through the NspS–MbaA signaling system. We found that this effect probably occurs through a direct interaction of spermine with NspS, as purified NspS protein could bind spermine in vitro. Spermine also inhibited biofilm formation by altering the transcription of the vps genes involved in biofilm matrix production. Global c-di-GMP levels were unaffected by spermine supplementation, suggesting that biofilm formation may be regulated by variations in local rather than global c-di-GMP pools. Finally, we propose a model illustrating how the NspS–MbaA signaling system may communicate exogenous polyamine content to the cell to control biofilm formation in the aquatic environment and within the human intestine.

Growth and Yield of Miscanthus × giganteus Grown in Fertilized and Biochar-Amended Soils in the Western North Carolina Mountains

ABSTRACT Miscanthus × giganteus Greef & Deu (giant miscanthus) is a perennial C4 grass grown worldwide for bioenergy production; however, there is concern about whether it can produce high yields on marginal soils in a temperate climate. The goals of this study were to determine whether giant miscanthus could establish and produce yields in Western North Carolina comparable to those in other regions and to determine whether fertilization and biochar could improve yields. At two field sites, Mills River (650 m) and Valle Crucis (830 m), fertilizer (0 and 100 kg NPK ha−1) and biochar (0 and 15 t ha−1) treatments were employed in a fully randomized block design. Genetically identical rhizomes were planted in spring of 2012 and allowed to grow for two growing seasons. No treatment effects were found for gas exchange, but rates were higher at Mills River than at Valle Crucis. There were no biochar or fertilizer effects on yields. First-year yields were greater at Mills River than at Valle Crucis (2.93 and 1.77 Mg dry weight [DW] ha−1, respectively). Overwinter survival rates were 100% at both field sites. Second-year yields were approximately 10× greater than in the first year (27.68 Mg DW ha−1 at Mills River vs. 30.12 Mg DW ha−1 at Valle Crucis). The high survival and growth rates during the first 2 yr demonstrate that this bioenergy crop is capable of growing in Western North Carolina and producing yields comparable to those in other areas of the country where this crop has been grown.