Topic
Transpiration
About: Transpiration is a research topic. Over the lifetime, 15867 publications have been published within this topic receiving 548147 citations.
Papers published on a yearly basis
Papers
More filters
•
TL;DR: Progress towards a reconciliation of parallel concepts in meteorology and physiology is described, which stresses the importance of physiological restraint on the rate of transpiration from an irrigated field surrounded by dry land.
Abstract: A turgid leaf exposed to bright sunshine can transpire an amount of water several times its own weight during a summer day. Rapid evaporation is sustained by a supply of heat from the atmosphere and by a movement of water within the plant preventing the desiccation of leaf tissue. In analysis, the need for energy and the need for water have often been disassociated. Meteorologists investigating the energetics of transpiration have assumed that leaves behave like pieces of wet, green blotting paper, and plant physiologists have demonstrated mechanisms for the conduction of water at arbitrary rates unrelated to the physics of the environment. This paper describes progress towards a reconciliation of parallel concepts in meteorology and physiology. The path for the diffusion of water vapour from leaf cells to the free atmosphere is divided into two parts, one determined primarily by the size and distribution of stomata, and the other by wind speed and the aerodynamic properties of the plant surface. Diffusive resistances for single leaves and for plant communities are established from measurements in the laboratory and in the field and are then used: (i) to predict relative rates of evaporation from leaves with wet and dry surfaces; (ii) to investigate the dependence of transpiration rate on wind speed and surface roughness; (iii) to demonstrate that the relation between transpiration rate and lead area is governed by stomatal closure in leaves well shaded from sunlight; (iv) to calculate maximum rates of transpiration for different crops and climates. A final section on the convection of dry air stresses the importance of physiological restraint on the rate of transpiration from an irrigated field surrounded by dry land.
4,686 citations
••
TL;DR: A method is described which permits measurement of sap pressure in the xylem of vascular plants, and finds that in tall conifers there is a hydrostatic pressure gradient that closely corresponds to the height and seems surprisingly little influenced by the intensity of transpiration.
Abstract: A method is described which permits measurement of sap pressure in the xylem of vascular plants. As long predicted, sap pressures during transpiration are normally negative, ranging from -4 or -5 atmospheres in a damp forest to -80 atmospheres in the desert. Mangroves and other halophytes maintain at all times a sap pressure of -35 to -60 atmospheres. Mistletoes have greater suction than their hosts, usually by 10 to 20 atmospheres. Diurnal cycles of 10 to 20 atmospheres are common. In tall conifers there is a hydrostatic pressure gradient that closely corresponds to the height and seems surprisingly little influenced by the intensity of transpiration. Sap extruded from the xylem by gas pressure on the leaves is practically pure water. At zero turgor this procedure gives a linear relation between the intracellular concentration and the tension of the xylem.
4,079 citations
••
TL;DR: In this paper, a two-stream approximation model of radiative transfer was used to calculate values of hemispheric canopy reflectance in the visible and near-infrared wavelength intervals.
Abstract: A two-stream approximation model of radiative transfer is used to calculate values of hemispheric canopy reflectance in the visible and near-infrared wavelength intervals. Simple leaf models of photosynthesis and stomatal resistance are integrated over leaf orientation and canopy depth to obtain estimates of canopy photosynthesis and bulk stomatal or canopy resistance. The ratio of near-infrared and visible reflectances is predicted to be a near linear indicator of minimum canopy resistance and photosynthetic capacity but a poor predictor of leaf area index or biomass.
2,198 citations
••
01 Jan 1987TL;DR: In this article, a linear correlation between stomatal conductance (g) and CO2 assimilation rate (A) has been reported when photon fluence was varied and when the photosynthetic capacity of leaves was altered by growth conditions, provided CO2, air humidity and leaf temperature were constant.
Abstract: In the past, stomatal responses have generally been considered in relation to single environmental variables in part because the interactions between factors have appeared difficult to quantify in a simple way A linear correlation between stomatal conductance (g) and CO2 assimilation rate (A) has been reported when photon fluence was varied and when the photosynthetic capacity of leaves was altered by growth conditions, provided CO2, air humidity and leaf temperature were constant (1) Temperature and humidity are, however, not consistent in nature Lack of a concise description of stomatal responses to combinations of environmental factors has limited attempts to integrate these responses into quantitative models of leaf energy balance, photosynthesis, and transpiration Moreover, this lack has hindered progress toward understanding the stomatal mechanism We have taken a multi-variant approach to the study of stomatal conductance and we show that under many conditions the responses of stornata can be described by a set of linear relationships This model can be linked to models of leaf carbon metabolism and the environment to predict fluxes of CO2, H2O and energy In this paper, we show how the model of conductance can be linked to a description of CO2 assimilation as a function of intercellular CO2 (whether empirical or the output of a model) to predict the distribution of flux control between the stornata and leaf “biochemistry” under conditions in a gas-exchange cuvette
2,176 citations
••
TL;DR: In this article, a system of models for the simulation of gas and energy exchange of a leaf of a C3 plant in free air is presented, where the physiological processes are simulated by sub-models that: (a) give net photosynthesis (An) as a function of environmental and leaf parameters and stomatal conductance (gs); (b) give g, as well as the concentration of CO2 and H2O in air at the leaf surface and the current rate of photosynthesis of the leaf.
2,030 citations