Estimates of net photosynthetic parameters for twelve tree species in mature forests of the southern Appalachians

Leaf gas exchange, temperature, and incident radiation were measured in situ for 20 mature trees of 12 deciduous species spanning a range of heights from 7.9 to 30.1 m and growing in the southern Appalachian Mountains. Air temperature, water vapor pressure, total radiation, photosynthetically active radiation, and carbon dioxide concentration were also measured. Estimated mean, light-saturated net assimilation rates ( micro mol m(-2) s(-1)) were: Quercus coccinea Muenchh. (10.3), Q. prinus L. (9.9), Q. rubra L. (8.9), Betula lenta L. (8.1), Liriodendron tulipifera L. (7.9), Q. alba L. (7.6), Carya glabra Mill. (7.2), Acer rubrum L. (5.6), Nyssa sylvatica Marsh. (3.9), Cornus florida L. (3.5), and Acer pensylvanicum L. (1.7). There were significant differences in both net assimilation rates and quantum yield efficiencies between species, with the understory species C. florida and A. pensylvanicum exhibiting lower net assimilation rates at saturation and higher estimated quantum yield efficiencies than the other species. Average temperature and light decreased from the canopy top to bottom, whereas ambient CO(2) concentration increased, and vapor pressure and vapor pressure deficits were inconsistent. We observed curvilinear effects of temperature and vapor pressure deficit on net assimilation response to light, and these effects varied by species. Errors in predicted net assimilation ranged from 1 to 3 micro mol m(-2) s(-1) under the environmental conditions prevailing during the study.     

Element accumulation patterns of deciduous and evergreen tree seedlings on acid soils: implications for sensitivity to manganese toxicity

Foliar nutrient imbalances, including the hyperaccumulation of manganese (Mn), are correlated with symptoms of declining health in sensitive tree species growing on acidic forest soils. The objectives of this study were to: (1) compare foliar nutrient accumulation patterns of six deciduous (sugar maple (Acer saccharum Marsh.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), white oak (Quercus alba L.), black cherry (Prunus serotina Ehrh.) and white ash (Fraxinus americana L.)) and three evergreen (eastern hemlock (Tsuga canadensis L.), white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss.)) tree species growing on acidic forest soils; and (2) examine how leaf phenology and other traits that distinguish evergreen and deciduous tree species influence foliar Mn accumulation rates and sensitivity to excess Mn. For the first objective, leaf samples of seedlings from five acidic, non-glaciated field sites on Pennsylvania's Allegheny Plateau were collected and analyzed for leaf element concentrations. In a second study, we examined growth and photosynthetic responses of seedlings exposed to excess Mn in sand culture. In field samples, Mn in deciduous foliage hyperaccumulated to concentrations more than twice as high as those found in evergreen needles. Among species, sugar maple was the most sensitive to excess Mn based on growth and photosynthetic measurements. Photosynthesis in red maple and red oak was also sensitive to excess Mn, whereas white oak, black cherry, white ash and the three evergreen species were tolerant of excess Mn. Among the nine species, relative rates of photosynthesis were negatively correlated with foliar Mn concentrations, suggesting that photosynthetic sensitivity to Mn is a function of its rate of accumulation in seedling foliage.     

Living on the forests: Women and household security in Nigeria

A survey was conducted to obtain information about the use of forest products by rural women for sustaining food and financial security at household level in the Nigerian rainforest zone. Data analysis reveals that the rural women are heavily engaged in harvesting, processing and marketing of forest products; collection of forest products is a specialised activity based on acquired skills and an ecological knowledge of the forests; and collection of medicinal plants is shrewd in secrecy and involves the performance of rituals. Net income generated from natural forests by rural women in the study area varies from about N23,000 to N113,080 per household per season. Forest regeneration has received little attention from both the rural communities and government and this tends to undermine sustained use of the forests.     

The importance of seedling competition in the segregation of spruce and fir in the southern Appalachians

Fraser fir (Abies fraseri [Pursh] Poir.) and red spruce (Picea rubens Sarg.) are codominants of southern Appalachian spruce-fir forests. Fraser fir generally dominates above 1740 m, while red spruce usually dominates below this elevation. This study was designed to determine whether the present segregation of the two species along elevational gradients is associated with seedling competition or contrasting physiological responses to environmental factors. Seedlings were grown for two years in a replacement series experiment along two elevational transects extending from 1300 m to 1900 m, and harvested for growth analysis.Competition increased with decreasing elevation and Fraser fir was apparently the stronger competitor. Mortality was inversely correlated with elevation and was most evident in red spruce in May, and in fir in late summer. Fir growth increased with elevation and red spruce grew most at the middle elevation (1600 m). Neither competitive interactions nor growth responses completely explained the elevational segregation of red spruce and Fraser fir. We hypothesize that the early-successional Fraser fir quickly dominates at higher elevations following disturbance and that continued disturbance will favor its dominance at higher elevations. However, the late-successional noncompetitive red spruce slowly establishes itself and, while consistently present, may only dominate in the absence of disturbance and where other species are at the margins of their distribution.     

Towards dsRNA-integrated protection of medical Cannabis crops: considering human safety,recent- and developing RNAi methods,and research inroads

Owing to the expanding industry of medical Cannabis, we discuss recent milestones in RNA interference (RNAi)-based crop protection research and development that are transferable to medical Cannabis cultivation. Recent and prospective increases in pest pressure in both indoor and outdoor Cannabis production systems, and the need for effective nonchemical pest control technologies (particularly crucial in the context of cultivating plants for medical purposes), are discussed. We support the idea that developing RNAi tactics towards protection of medical Cannabis could play a major role in maximizing success in this continuously expanding industry. However, there remain critical knowledge gaps, especially with regard to RNA pesticide biosafety from a human toxicological viewpoint, as a result of the medical context of Cannabis product use. Furthermore, efforts are needed to optimize transformation and micropropagation of Cannabis plants, examine cutting edge RNAi techniques for various Cannabis–pest scenarios, and investigate the combined application of RNAi- and biological control tactics in medical Cannabis cultivation. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Computed tomography assisted diagnosis and treatment of a comminuted fracture of the plantar aspect of the medial trochlear ridge and the proximal tubercle of the talus in a foal

Isolated fractures of the proximal tubercle of the talus and the medial trochlear ridge of the talus have been reported in the equine literature. A comminuted, intra-articular fracture of the plantar medial trochlear ridge and proximal tubercle of the talus has not been previously reported. The current case report describes this unique comminuted fracture in a 6-week-old Thoroughbred foal with acute onset lameness. The diagnosis was achieved by a combination of radiography, ultrasonography and computed tomography (CT) followed by CT arthrography. Surgical removal of the fracture fragments was recommended; the intra-articular fracture fragments were removed under arthroscopic visualisation of the plantar pouch of the tarsocrural joint; due to ligamentous attachments and partial extra-articular nature, the fracture fragment of the proximal tubercle of the talus was removed via an arthrotomy extension of the medial arthroscopy portal. On follow-up examination 12 months post-operatively, the yearling showed no clinical evidence of lameness or radiographic evidence of secondary degenerative joint disease.     

Increased drug concentration and repeated eye drop administration as strategies to optimize topical drug delivery: A fluorophotometric study in healthy dogs

Objectives

Determine tear film kinetics with different fluorescein concentrations and repeated eye drop administration at various time intervals.

Animals Studied

Six healthy Beagles.

Procedures

Six experiments were conducted on separate days: single eye drop administration (control) or two separate eye drops administered at 30 s, 1, 2, 5, and 10 min intervals. For each experiment, one eye received 0.3% fluorescein solution while the other eye received 1% fluorescein solution, and tear fluid was collected with capillary tubes at 0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, and 180 min. Fluorescein concentrations were measured using automated fluorophotometry.

Results

Compared with 0.3% solution, eyes receiving 1% fluorescein solution had significantly higher tear film concentrations (p ≤ .046) and the area-under-the-fluorescein-time curve was twofold greater (p = .005). Compared with control: (i) Tear film concentrations were significantly higher for up to 20 min when repeating administration 30 s to 5 min after the first drop (p ≤ .006); (ii) The highest increase in area-under-the-curve was obtained with 2 and 5 min intervals for 0.3% (+109%–130%) and 1% solutions (+153%–157%); (iii) The highest increase in median precorneal retention time (defined as tear film concentration < 5% from baseline values) was obtained with 5 min intervals for 0.3% (55 min vs. 15 min in control) and 2–5 min intervals for 1% solutions (50 min vs. 25 min in control).

Conclusions

Drug delivery to the ocular surface can be enhanced by using more concentrated formulations and/or by repeating eye drop administration 2–5 min after the first dose.     

Comparison of ultrasonography, radiography and a single computed tomography slice for fluid identification within the feline tympanic bulla

Evaluation of the tympanic bulla (TB) in cases of acute feline otitis media can be a diagnostic challenge, although a feature often associated with this condition is the accumulation of fluid or material within the middle ear cavity. A technique is reported allowing optimum imaging of the feline TB using ultrasound (US) and recording of the appearance of gas and fluid-filled TB. A random number of bullae in 42 feline cadavers were filled with lubricant and rostroventral-caudodorsal oblique radiographs, single slice computed tomography (CT) images and US images were created and interpreted by blinded operators. The content (fluid or gas) of each TB was determined using each technique and the cadavers were then frozen and sectioned for confirmation. CT remained the most accurate diagnostic method, but US produced better results than radiology. Given the advantages of US over other imaging techniques, these results suggest that further work is warranted to determine applications of this modality in the evaluation of clinical cases of feline otitis media.