scholarly journals Structural Adaptations in Overwintering Leaves of Thermonastic and Nonthermonastic Rhododendron Species

2008 ◽  
Vol 133 (6) ◽  
pp. 768-776 ◽  
Author(s):  
Xiang Wang ◽  
Rajeev Arora ◽  
Harry T. Horner ◽  
Stephen L. Krebs
Keyword(s):  
Stomatal Density ◽  
Eastern United States ◽  
Cold Temperatures ◽  
Unit Leaf ◽  
Additional Layer ◽  
Landscape Plants ◽  
Photooxidative Damage ◽  
Avoidance Strategy ◽  
Structural Adaptations ◽  
Desiccation Avoidance

Evergreen rhododendrons (Rhododendron L.) are important woody landscape plants in many temperate zones. During winters, leaves of these plants frequently are exposed to a combination of cold temperatures, high radiation, and reduced photosynthetic activity, conditions that render them vulnerable to photooxidative damage. In addition, these plants are shallow-rooted and thus susceptible to leaf desiccation when soils are frozen. In this study, the potential adaptive significance of leaf morphology and anatomy in two contrasting Rhododendron species was investigated. R. catawbiense Michx. (native to eastern United States) exhibits thermonasty (leaf drooping and curling at subfreezing temperatures) and is more winter-hardy [leaf freezing tolerance (LT50) of containerized plants ≈–35 °C], whereas R. ponticum L. (native to central Asia) is less hardy (LT50 ≈–16 °C), and nonthermonastic. Thermonasty may function as a light and/or desiccation avoidance strategy in rhododendrons. Microscopic results revealed that R. ponticum has significantly thicker leaf blades but thinner cuticle than R. catawbiense. There is one layer of upper epidermis and three layers of palisade mesophyll in R. catawbiense compared with two distinct layers of upper epidermis and two layers of palisade mesophyll in R. ponticum. We suggest that the additional layer of upper epidermis in R. ponticum and thicker cuticle and extra palisade layer in R. catawbiense represent structural adaptations for reducing light injury in leaves and could serve a photoprotective function in winter when leaf photochemistry is generally sluggish. Results also indicate that although stomatal density of R. ponticum is higher than that of R. catawbiense leaves, the overall opening of stomatal pores per unit leaf area (an integrated value of stomatal density and pore size) is higher by approximately twofold in R. catawbiense, suggesting that R. catawbiense may be more prone to winter desiccation and that thermonasty may be a particularly beneficial trait in this species by serving as a desiccation-avoidance strategy in addition to a photoprotection role.

Stomatal Development During Leaf Expansion in Tobacco and Sunflower

1975 ◽  
Vol 23 (2) ◽  
pp. 253 ◽  
Author(s):  
HM Rawson ◽  
CL Craven
Keyword(s):  
Leaf Area ◽  
Stomatal Density ◽  
Stomatal Development ◽  
Developmental Patterns ◽  
Full Size ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Wide Range ◽  
Young Leaves ◽  
Different Levels

Changes in stomatal density and size were followed in tobacco and sunflower leaves expanding from 10% of final area (10% Amax) to Amax under different levels of radiation. Lower radiation increased final leaf area, reduced stomatal densities, and increased area per stoma but had little effect on stomatal area per unit leaf area at Amax. In very young leaves (20% Amax) there was a wide range in the sizes of individual stomata, some stomata being close to full size, but by Amax differences were small. The possible relationship between the developmental patterns described and photosynthesis is briefly discussed.

Photosynthetic responses of black walnut (Juglansnigra) to shading

1982 ◽  
Vol 12 (4) ◽  
pp. 725-730 ◽  
Author(s):  
T. J. Dean ◽  
S. G. Pallardy ◽  
G. S. Cox
Keyword(s):  
Leaf Area ◽  
Quantum Efficiency ◽  
Stomatal Density ◽  
Black Walnut ◽  
Response Curves ◽  
Gross Photosynthesis ◽  
Total Transmission ◽  
Unit Leaf ◽  
Photosynthetic Responses ◽  
Artificial Shading

Photosynthetic characteristics and morphology of leaves of black walnut (Juglansnigra L.) seedlings grown under different types and degrees of shade were investigated by measuring insitu gross photosynthesis (Ps) and by microscopic study of leaf material. During the growing season of 1979, seedlings were subjected to artificial shading of two types: the first type simulated two overstory densities (leaf-area indices of 1 and 2) with corresponding proportions of sunflecks and total transmission of 50 and 21%, respectively, of incident photosynthetically active radiation (PAR, 400–700 nm); the second consisted of two densities of greenhouse shading screen which transmitted approximately 16 and 3% of incident PAR. From quantum efficiency values derived from Ps – quantum flux density response curves it was determined that the walnut seedlings adjusted photosynthetically to shade. Quantum efficiency increased as much as 44% with the densest shading. Light-saturated Ps did not appear to decline with increased shading if sunflecks were present, and it declined only 18% under complete shade that transmitted about 16% of incident PAR. Estimated daily photosynthesis per unit leaf area for black walnut growing under heavy and complete shade (3% of incident PAR) was nearly one-half that of the unshaded control. Shading resulted in plants that possessed leaves that were thinner, had less palisade mesophyll, had lower stomatal density, and had more chlorophyll per unit of leaf area. These data indicate that black walnut seedlings have the capacity for substantial photosynthesis under shade and may be more shade tolerant than silvicultural classifications suggest.

scholarly journals First Report on Establishment of Laricobius osakensis (Coleoptera: Derodontidae), a Biological Control Agent for Hemlock Woolly Adelgid, Adelges tsugae (Hemiptera: Adelgidae), in the Eastern U.S.

Forests ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 496 ◽  
Author(s):  
Ashley Toland ◽  
Carlyle Brewster ◽  
Katlin Mooneyham ◽  
Scott Salom
Keyword(s):  
United States ◽  
Biological Control ◽  
Biological Control Agent ◽  
Polar Vortex ◽  
Hemlock Woolly Adelgid ◽  
Control Agent ◽  
Adelges Tsugae ◽  
Eastern United States ◽  
Cold Temperatures ◽  
Eastern Usa

The hemlock woolly adelgid (HWA) is an invasive insect species native to Japan causing significant hemlock mortality in the eastern United States. Laricobius spp. have been targeted as biological control agents because they are adelgid specialists. Laricobius osakensis Montgomery and Shiyake is native to the same region of Japan from which the strain of HWA found in the eastern United States originated. Studies in Japan found that it is phenologically synchronous with HWA. Following approval to release L. osakensis from quarantine in 2010, approximately 32,000 were released at a total of 61 sites starting in 2012. In winter of 2014 and 2015, periods of extreme cold temperatures throughout the eastern USA, as well as the polar vortex, resulted in extensive mortality to HWA, which likely delayed the establishment of L. osakensis. The ability of the beetle to survive and establish in the eastern United States is reported here. In the first year of this study (2015–2016), limited numbers of L. osakensis were recovered, as HWA populations were still rebounding. In the second year (2016–2017), 147 L. osakensis were collected at 5 of 9 sites sampled, coinciding with rebounding HWA populations. Larval recovery was much greater than adult recovery throughout the study. HWA density was directly correlated with warmer plant hardiness zones and recovery of Laricobius beetles was significantly correlated with HWA density. Our results suggest that L. osakensis is successfully establishing at several of the sampled release sites and that the best predictor of its presence at a site is the HWA density.

scholarly journals Thermal Tolerance of Gloomy Scale (Hemiptera: Diaspididae) in the Eastern United States

2020 ◽  
Vol 49 (1) ◽  
pp. 104-114 ◽  
Author(s):  
Michael G Just ◽  
Steven D Frank
Keyword(s):  
Thermal Tolerance ◽  
Acer Rubrum ◽  
Eastern United States ◽  
Red Maple ◽  
Southern Boundary ◽  
Cold Temperatures ◽  
Distribution Boundary ◽  
Scale Population ◽  
Cold Tolerant ◽  
Temperature Exposure

Abstract An insect species’ geographic distribution is probably delimited in part by physiological tolerances of environmental temperatures. Gloomy scale (Melanaspis tenebricosa (Comstock)) is a native insect herbivore in eastern U.S. forests. In eastern U.S. cities, where temperatures are warmer than nearby natural areas, M. tenebricosa is a primary pest of red maple (Acer rubrum L.; Sapindales: Sapindaceae) With warming, M. tenebricosa may spread to new cities or become pestilent in forests. To better understand current and future M. tenebricosa distribution boundaries, we examined M. tenebricosa thermal tolerance under laboratory conditions. We selected five hot and five cold experimental temperatures representative of locations in the known M. tenebricosa distribution. We built models to predict scale mortality based on duration of exposure to warm or cold experimental temperatures. We then used these models to estimate upper and lower lethal durations, i.e., temperature exposure durations that result in 50% mortality. We tested the thermal tolerance for M. tenebricosa populations from northern, mid, and southern locations of the species’ known distribution. Scales were more heat and cold tolerant of temperatures representative of the midlatitudes of their distribution where their densities are the greatest. Moreover, the scale population from the northern distribution boundary could tolerate cold temperatures from the northern boundary for twice as long as the population collected near the southern boundary. Our results suggest that as the climate warms the M. tenebricosa distribution may expand poleward, but experience a contraction at its southern boundary.

scholarly journals What is the influence of ordinary epidermal cells and stomata on the leaf plasticity of coffee plants grown under full-sun and shady conditions?

2010 ◽  
Vol 70 (4) ◽  
pp. 1083-1088 ◽  
Author(s):  
MF. Pompelli ◽  
SCV. Martins ◽  
EF. Celin ◽  
MC. Ventrella ◽  
FM. DaMatta
Keyword(s):  
Epidermal Cell ◽  
Stomatal Density ◽  
Land Plant ◽  
Epidermal Cells ◽  
Stomatal Index ◽  
Unit Leaf ◽  
Leaf Plasticity ◽  
Coffee Plants ◽  
Sun Leaves ◽  
Lower Irradiance

Stomata are crucial in land plant productivity and survival. In general, with lower irradiance, stomatal and epidermal cell frequency per unit leaf area decreases, whereas guard-cell length or width increases. Nevertheless, the stomatal index is accepted as remaining constant. The aim of this paper to study the influence of ordinary epidermal cells and stomata on leaf plasticity and the influence of these characteristics on stomata density, index, and sizes, in the total number of stomata, as well as the detailed distribution of stomata on a leaf blade. As a result, a highly significant positive correlation (R²a = 0.767 p < 0.001) between stomatal index and stomatal density, and with ordinary epidermal cell density (R²a = 0.500 p < 0.05), and a highly negative correlation between stomatal index and ordinary epidermal cell area (R²a = -0.571 p < 0.001), were obtained. However in no instance was the correlation between stomatal index or stomatal density and stomatal dimensions taken into consideration. The study also indicated that in coffee, the stomatal index was 19.09% in shaded leaves and 20.08% in full-sun leaves. In this sense, variations in the stomatal index by irradiance, its causes and the consequences on plant physiology were discussed.

scholarly journals Fungi in Landscape Mulches—Are They a Problem?

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 493B-493
Author(s):  
Larry J. Kuhns ◽  
Elizabeth A. Brantley ◽  
Donald D. Davis
Keyword(s):  
United States ◽  
Research Program ◽  
Health Hazards ◽  
Fruiting Bodies ◽  
Eastern United States ◽  
Insurance Claims ◽  
Slime Molds ◽  
Landscape Plants ◽  
Exchange Information ◽  
The Masses

Homeowners are often troubled by the presence of slime molds, stinkhorns, and mushrooms growing in their landscape mulches; but, they are not harmful to landscape plants, and no known health hazards are associated with them unless they are eaten. They can be discarded or ignored and they will quickly decompose. The fruiting bodies of the artillery fungus are barely visible (tiny cream or orange-brown cups approximately 1/10 of an inch in diameter), but they are the source of serious problems, many of which have resulted in insurance claims and lawsuits. They are phototropic and orient themselves toward bright surfaces, such as light-colored siding on homes and automobiles. They “shoot” their black, sticky spore masses, which can be windblown to the second story of a house. The masses stick to the side of buildings and automobiles, resembling small specks of tar. Once in place, the spore masses are very difficult to remove without damaging the surface to which they are attached. When removed, a stain remains. A few of the spots are barely noticeable, but, as they accumulate, they may become very unsightly. To date, there are no known controls for this fungus, but a research program studying possible solutions has been initiated. We ask that anyone who has information or experience with the artillery fungus contact us to exchange information. A brochure describing the four common types of fungi growing in landscape mulches in the eastern United States—mushrooms, slime molds, bird's nest fungus, and the artillery fungus—has also been prepared to educate consumers.

Adaptations of strangler figs to life in the rainforest canopy

2006 ◽  
Vol 33 (5) ◽  
pp. 465 ◽  
Author(s):  
Susanne Schmidt ◽  
Dieter P. Tracey
Keyword(s):  
Leaf Area ◽  
Extreme Values ◽  
Stomatal Density ◽  
Keystone Species ◽  
Nitrate Assimilation ◽  
Experimental System ◽  
Standing Tree ◽  
Free Standing ◽  
Unit Leaf ◽  
Taxonomic Groups

Figs are rainforest keystone species. Non-strangler figs establish on the forest floor; strangler figs establish epiphytically, followed by a dramatic transition from epiphyte to free-standing tree that kills its hosts. Free-standing figs display vigorous growth and resource demand suggesting that epiphytic strangler figs require special adaptations to deal with resource limitations imposed by the epiphytic environment. We studied epiphytic and free-standing strangler figs, and non-strangler figs in tropical rainforest and in cultivation, as well as strangler figs in controlled conditions. We investigated whether the transition from epiphyte to free-standing tree is characterised by morphological and physiological plasticity. Epiphyte substrate had higher levels of plant-available ammonium and phosphate, and similar levels of nitrate compared with rainforest soil, suggesting that N and P are initially not limiting resources. A relationship was found between taxonomic groups and plant N physiology; strangler figs, all members of subgenus Urostigma, had mostly low foliar nitrate assimilation rates whereas non-strangler figs, in subgenera Pharmacocycea, Sycidium, Sycomorus or Synoecia, had moderate to high rates. Nitrate is an energetically expensive N source, and low nitrate use may be an adaptation of strangler figs for conserving energy during epiphytic growth. Interestingly, significant amounts of nitrate were stored in fleshy taproot tubers of epiphytic stranglers. Supporting the concept of plasticity, leaves of epiphytic Ficus benjamina L. had lower N and C content per unit leaf area, lower stomatal density and 80% greater specific leaf area than leaves of conspecific free-standing trees. Similarly, glasshouse-grown stranglers strongly increased biomass allocation to roots under water limitation. Epiphytic and free-standing F. benjamina had similar average foliar δ13C, but epiphytes had more extreme values; this indicates that both groups of plants use the C3 pathway of CO2 fixation but that water availability is highly variable for epiphytes. We hypothesise that epiphytic figs use fleshy stem tubers to avoid water stress, and that nitrate acts as an osmotic compound in tubers. We conclude that strangler figs are a unique experimental system for studying the transition from rainforest epiphyte to tree, and the genetic and environmental triggers involved.

The use of scanning electron microscopy in interpreting chenopodium remains from three archaeological sites in northwestern Iowa

1992 ◽  
Vol 50 (2) ◽  
pp. 1112-1113
Author(s):  
Douglas William Jones
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Archaeological Sites ◽  
Late Prehistoric ◽  
Eastern United States ◽  
Chenopodium Berlandieri ◽  
Seed Identification ◽  
Level 2 ◽  
Scanning Electron

Within the past 20 years, archaeobotanical research in the Eastern United States has documented an early agricultural complex before the dominance of the Mesoamerican domesticates (corn, beans, and squash) in late prehistoric and historic agricultural systems. This early agricultural complex consisted of domesticated plants such as Iva annua var.macrocarpa (Sumpweed or Marshelder), Hellanthus annuus (Sunflower) and Chenopodium berlandieri, (Goosefoot or Lasbsquarters), and heavily utilized plants such as Polygonum erectum (Erect Knotweed), Phalaris caroliniana (May grass), and Hordeum pusillum (Little Barley).Recent research involving the use of Scanning Electron Microscopy (SEM) specifically on Chenopodium has established diagnostic traits of wild and domesticated species seeds. This is important because carbonized or uncarbonized seeds are the most commonly recovered Chenopodium material from archaeological sites. The diagnostic seed traits assist archaeobotanists in identification of Chenopodium remains and provide a basis for evaluation of Chenopodium utilization in a culture's subsistence patterns. With the aid of SEM, an analysis of Chenopodium remains from three Late Prehistoric sites in Northwest Iowa (Blood Run [Oneota culture], Brewster [Mill Creek culture], and Chan-Ya-Ta [Mill Creek culture]) has been conducted to: 1) attempt seed identification to a species level, 2) evaluate the traits of the seeds for classification as either wild or domesticated, and 3) evaluate the role of Chenopodium utilization in both the Oneota and Mill Creek cultures.

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