Convection Phenomena From Plants in Still Air

Gates, David M.; Benedict, Charles M.

doi:10.1002/j.1537-2197.1963.tb07229.x

Cited by 32 publications

(9 citation statements)

References 9 publications

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“…Air temperature influences the energy content or temperature of a plant by the convection of energy to or from the plant. A detailed discussion of this influence is given by Gates (1962) and by Gates and Benedict ( 1963). The temperature of a plant is nearly always different than the air surrounding the plant.…”

Section: Transfer Mechanismsmentioning

confidence: 99%

Energy, Plants, and Ecology

Gates¹

1965

Ecology

Self Cite

232

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The environmental factors affecting the flow of energy between a plant and its environment are described. These factors are solar and thermal radiation, air temperature, water vapor density of the air, and wind speed. The mechanisms of radiation, convection, and transpiration which transfer energy between the plant and the environment are expressed in analytical form. An example is given of a 24—hour cycle for a plant illustrating the daily variation of each of these factors and of the resulting plant temperature. Basic plant properties, such as absorptance to radiation, convection coefficient, and water vapor diffusion resistance, determine the extent to which the environment influences the energy content and temperature of the plant. Photosynthesis is light and temperature dependent, and other physiological processes are temperature dependent only. Maxima and minima in photosynthetic activity occur during a day as a consequence of changes in light intensity and leaf temperature produced by varying environmental conditions. The ecological significance of these environmentally influenced physiological processes is enormous in terms of productivity and competition.

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Section: Transfer Mechanismsmentioning

confidence: 99%

Energy, Plants, and Ecology

Gates¹

1965

Ecology

Self Cite

232

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“…Some recent canopy reflectance models (Knyazikhin et al, 1998;Kuusk & Nilson, 2000;Shabanov et al, 2000) have accounted for the effect of smallscale clumping by modifying the G-function but in these approaches the shoot has not been explicitly used as the basic element in evaluating the area scattering phase function of the transport equation. The presence of within-shoot multiple scattering has long been recognized (Gates & Benedict, 1963;Norman & Jarvis, 1975), but in order to take it into account in radiative transfer models, it is necessary to derive quantitative relationships between the structure and the scattering properties of a shoot.…”

Section: Introductionmentioning

confidence: 99%

A method to account for shoot scale clumping in coniferous canopy reflectance models

Smolander¹,

Stenberg²

2003

Remote Sensing of Environment

125

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The three-dimensional structure of a coniferous shoot gives rise to multiple scattering of light between the needles of the shoot, causing the shoot spectral reflectance to differ from that of a flat leaf. Forest reflectance models based on the radiative transfer equation handle shoot level clumping by correcting the radiation attenuation coefficient with a clumping index. The clumping index causes a reduction in the interception of radiation by the canopy at a fixed leaf area index (LAI). In this study, we show how within-shoot multiple scattering is related to shoot scale clumping and derive a similar, but wavelength dependent, correction to the scattering coefficient. The results provide a method for integrating shoot structure into current radiative transfer equation based forest reflectance models. The method was applied to explore the effect of shoot scale clumping on canopy spectral reflectance using simple model canopies with a homogeneous higher level structure. The clumping of needles into shoots caused a wavelength dependent reduction in canopy reflectance, as compared to that of a leaf canopy with similar interception. This is proposed to be one reason why coniferous and broad-leaved canopies occupy different regions in the spectral space and exhibit different dependency of spectral vegetation indices on LAI. D

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“…Cacti have a relatively high heat capacity and a small surface-to-volume ratio, resulting in inefficient heat dissipation by convection (Gates and Benedict 1963). Morphological features such as size, stem orientation, spine coverage, and ribbing may ameliorate tissue temperature extremes by affecting energy exchange with the environment (Hadley 1972, Nobel 1978.…”

Section: Introductionmentioning

confidence: 99%

High‐Temperature Responses of North American Cacti

Smith¹,

Didden-Zopfy²,

Nobel³

1984

Ecology

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High—temperature tolerances of 14 species of North American cacti were investigated. A reduction in the proportion of chlorenchyma cells taking up a vital stain (neutral red) and reduced nocturnal acid accumulation were used as indicators of high—temperature damage. All species tolerated relatively high tissue temperatures, the mean maximum tolerance being 64°C, with an absolute maximum of 69° for two species of Ferocactus. Such tissue tolerances to high temperature may be unsurpassed in vascular plants. Morphological features can affect tissue temperatures. Specifically, thin—stemmed species such as the cylindropuntias attain lower maximum temperatures under identical microclimatic conditions than do more massive species; they also tend to be less tolerant of high—temperature stress. Stem diameter changes of three species of columnar ceroid cacti along a Sonoran Desert latitudinal transect were previously attributed to adaptation to progressively colder temperatures northward. Such changes can also be interpreted as a morphological adaptation to high temperatures, particularly in the southern Sonoran Desert. Interspecific differences in high—temperature tolerance may account for distributional differences among other species, e.g., the coastal—sage—inhabiting Ferocactus viridescens was less tolerant of high temperature than were the three Ferocactus species that inhabit desert regions. Acclimation of high—temperature tolerances in response to increasing day/night air temperatures was observed in all 14 species, especially at higher growth temperatures. From 40° day/30° night to 50°/40°, the tolerable tissue temperatures increased an average of 6°. Half—times for the acclimation shifts were 1—3 d. Although cacti attain extremely high tissue temperatures in desert habitats, tolerance of high temperatures and pronounced acclimation potential allow them to occur in some of the hottest habitats in North America.

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Convection Phenomena From Plants in Still Air

Cited by 32 publications

References 9 publications

Energy, Plants, and Ecology

Energy, Plants, and Ecology

A method to account for shoot scale clumping in coniferous canopy reflectance models

High‐Temperature Responses of North American Cacti

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