A new and simple greenhouse crop transpiration model enabling predictions from outdoor conditions is presented and the parameters involved are discussed with respect to different types of greenhouse-crop systems. This transpiration model was validated against experimental data measured in a soil-less tomato crop cultivation in Avignon in summer conditions, when the greenhouse is open, and early...

This study determined whether the field level concentration of root zone CO2 affects transpiration rate and root water transport in soybean (Glycine max L. Merr.). In an upland field converted from a paddy field, topsoil CO2 during the cropping season rose to 8 kPa of partial pressure after rainfall, whereas O2 dropped only to a minimum of 7 kPa. An elevated root zone CO2 pressure of 6 kPa sign...

Abstract. Viscous flow, effusion, and thermal transpiration are the main gas transport modalities for a rarefied gas in a macro-porous medium. They have been well quantified only in the case of simple geometries. This paper presents a numerical method based on the homogenization of kinetic equations producing effective transport properties (permeability, Knudsen diffusivity, thermal transpirati...

to diffuisive and turbulent vapor flux in the external air, a similar diffusive resistance which results from the internal leaf geometry, inclusive of the stomlata, and1 parallel to the latter, a resistance to vapor diffusion1 throu-gh the cuticle. In contrast. the last 2 resistances do not exist in the evaporation froml an open water sturface or a moist blotter paper. The resistanice in these ...

Stomatal complexes in the epidermes of aerial plant parts are critical sites for the regulation of gas exchange between the plant and the atmosphere. Stomata consist of microscopic pores, each flanked by a pair of guard cells. Guard cells can increase or decrease the size of the pore via changes in their turgor status, hence regulating both CO2 entry into the leaf and transpiration, or the loss...

At the leaf scale, it is a long-held assumption that stomata close at night in the absence of light, causing transpiration to decrease to zero. Energy balance models and evapotranspiration equations often rely on net radiation as an upper bound, and some models reduce evapotranspiration to zero at night when there is no solar radiation. Emerging research is showing, however, that transpiration ...

The use of potential transpiration models to simulate transpiration rates in areas prone to soil water deficits leads to overestimates of water use as the soil dries. Therefore, I carried out studies on Eucalyptus grandis W. Hill ex Maiden trees subjected to soil drying at two field sites in the Mpumalanga province of South Africa to determine the relation between transpiration rate and soil wa...

We investigated the extent of osmotic adjustment and changes in transpiration rate that occur in response to repeated cycles of water deficit stress in 6-year-old Thuja occidentalis L. (eastern white cedar) trees. Groups of trees were water-stress conditioned by repeated exposure to predetermined thresholds of nonlethal water stress by withholding water until the predawn water potential fell to...

The goal of the study was to explore hydraulic traits in a 4-year-old loblolly pine (Pinus taeda L.) plantation to better understand plasticity of this species to resource availability. The influence of a factorial combination of irrigation (130 mm year 1 versus 494 mm year ) and fertilization (0 kg N ha 1 year 1 versus 80 kg N ha 1 year ) on stand-level transpiration, canopy stomatal conductan...

A Jarvis based [Philos. Trans. R. Soc. London, Ser. B 273 (1976) 593] model of canopy stomatal conductance was evaluated in context of its application to simulating transpiration in a conifer forest covered watershed in the Central Sierra Nevada of California, USA. Parameters influencing stomatal conductance were assigned values using Monte Carlo sampling. Model calibration was conducted by eva...