Measuring Transpiration Resistance of Leaves

Bavel, C. H. M. van; Nakayama, F. S.; Ehrler, W. L.

doi:10.1104/pp.40.3.535

Cited by 140 publications

(49 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Stomatal diffusion resistances were determined with a diffusion resistance hygrometer, similar in design to those constructed by van Bavel, Nakayama, and Ehrler (24). The instrument was calibrated regularly, from 0.2 to 0.3 full scale, with evaporative discs constructed to lose water at a known, constant diffusional resistance.…”

Section: Methodsmentioning

confidence: 99%

Seasonal Patterns of Acid Metabolism and Gas Exchange in Opuntia basilaris

Szarek¹,

Ting²

1974

Plant Physiol.

116

View full text Add to dashboard Cite

Acid metabolism and gas exchange studies were conducted in situ on the cactus Opuntia basilaris Engelm. and Bigel. A pattern of significant seasonal variation was evident. The pattern was controlled by rainfall, which significantly influenced plant water potentials, total gas transfer resistances, and nocturnal organic acid synthesis. In winter and early spring, when plant water stress was mild, stomatal and mesophyll resistances remained low, permitting enhanced nocturnal assimilation of "CO2. The day/night accumulation of acidity was large during these seasons. In summer and fall, plant water stress was moderate, although soil water stress was severe. The nocturnal assimilation of "CO2 was very low during these seasons, even in stems with open stomata, indicating large mesophyll resistances restricting exogenous gas incorporation. The day night accumulation of acidity was reduced, and a low level of acid metabolism persisted throughout this period. The rapid response to a midsummer rainfall emphasizes the importance of plant water potential as a parameter controlling over-all metabolic activity. The seasonal variations of acid metabolism and gas exchange significantly influenced the efficiency of water use and carbon dioxide assimilation. Periods of maximal efficiency followed rainfall throughout the course of the year.Historically, succulents have been considered a group of plants with morphological and anatomical similarities, and recently this classification has been expanded to include physiological similarities (7,16

show abstract

Section: Methodsmentioning

confidence: 99%

Seasonal Patterns of Acid Metabolism and Gas Exchange in Opuntia basilaris

Szarek¹,

Ting²

1974

Plant Physiol.

116

View full text Add to dashboard Cite

show abstract

“…Various methods to measure transpiration in the field have long been employed and include weighing lysimeters [4], leaf or canopy conductance/resistance [5], and sap flow [6]. In practice, weighing lysimeters and canopy conductance instruments are expensive and impractical for any tree greater than a few meters in height.…”

Section: Introductionmentioning

confidence: 99%

How Reliable Are Heat Pulse Velocity Methods for Estimating Tree Transpiration?

Förster

2017

Forests

View full text Add to dashboard Cite

Transpiration is a significant component of the hydrologic cycle and its accurate quantification is critical for modelling, industry, and policy decisions. Sap flow sensors provide a low cost and practical method to measure transpiration. Various methods to measure sap flow are available and a popular family of methods is known as heat pulse velocity (HPV). Theory on thermal conductance and convection, that underpins HPV methods, suggests transpiration can be directly estimated from sensor measurements without the need for laborious calibrations. To test this accuracy, transpiration estimated from HPV sensors is compared with an independent measure of plant water use such as a weighing lysimeter. A meta-analysis of the literature that explicitly tested the accuracy of a HPV sensors against an independent measure of transpiration was conducted. Data from linear regression analysis was collated where an R 2 of 1 indicates perfect precision and a slope of 1 of the linear regression curve indicates perfect accuracy. The average R 2 and slope from all studies was 0.822 and 0.860, respectively. However, the overall error, or deviation from real transpiration values, was 34.706%. The results indicate that HPV sensors are precise in correlating heat velocity with rates of transpiration, but poor in quantifying transpiration. Various sources of error in converting heat velocity into sap velocity and sap flow are discussed including probe misalignment, wound corrections, thermal diffusivity, stem water content, placement of sensors in sapwood, and scaling of point measurements to whole plants. Where whole plant water use or transpiration is required in a study, it is recommended that all sap flow sensors are calibrated against an independent measure of transpiration.

show abstract

“…Cleaf -Ccup ra + ri rO + ri (1) During the past few years the water vapor diffusion porometer (1,4,8,9) has become a widely used tool for field studies of stomatal resistance, replacing, to a considerable degree, other types of porometers which measure viscous air flow or some other parameter.…”

mentioning

confidence: 99%

Leaf Temperature Effects on Measurements of Diffusive Resistance to Water Vapor Transfer

Morrow

Slatyer

1971

Plant Physiol.

View full text Add to dashboard Cite

ABSTRACTis low (ri = 1-2 sec cml). When Tleaf-Tup = 5 C, the ratio drops below 0.5. Under high leaf resistance conditions (rz = 10-50 sec cm-') the comparable ratios are approximately 0.9 and 0.7, respectively. sensor which is sensitive over a narrow range of relative humidity at the low end of the relative humidity range. In operation, the cup is dried by air from a silica gel dehydrator. It is then placed over the leaf. Transpiration proceeds, the humidity in the cup increases, and the time required for the sensor to respond over a narrow, prescribed (usually 1-2%) range is determined.Since the relative humidity at the sites of evaporation within the leaf is close to 100% (it is generally assumed to be the saturation vapor pressure at the leaf temperature [7]), and since the humidity sensor is observed over a narrow range at the low end of the relative humidity scale (say, 18-20%), the water vapor concentration difference from leaf to air is assumed to be constant during the period of measurement. Consequently, the transpiration rate (E) can be assumed to be steady during the period of measurement and inversely proportional to the time-lapse (At) which occurs as the sensor responds over the measurement range.Calibration is based on the frequently used transpiration equation:During the past few years the water vapor diffusion porometer (1,4,8,9) has become a widely used tool for field studies of stomatal resistance, replacing, to a considerable degree, other types of porometers which measure viscous air flow or some other parameter.The attraction of the diffusion porometer is that it measures the actual diffusive resistance of the leaf to water vapor movement, and the transfer processes and pathways that are involved are essentially the same as in natural transpiration. These where eleaf (mm Hg) is the saturation vapor pressure at Tleaf and ecup (mm Hg) is the actual vapor pressure at the mid-point of the measurement range, and at Tcup; Cleaf and ccup (g cm-') are the corresponding water vapor concentrations. The coefficient a converts vapor pressure in mm Hg to water vapor concentration in g cm73. (It has the value 2.89 X 104 e/T when T is in degrees Kelvin). The term ra (sec cm7l) is the diffusive resistance external to the leaf (i.e., of the porometer cup itself) and r1 (sec cm-l) is the diffusive resistance of the leaf. Since E = k/At, where k is a coefficient of proportionality, this expression can be rewritten asAt any one level of Tleaf and T,u,X the right hand side of equation (2) is a constant, so (ra + rl) can be uniquely determined, for any one porometer system, by measurements of At. Calibration is generally carried out by determining At when the porometer is located over a range of perforated Plexiglas plates, the diffusive resistance of which is calculated from diffusion theory (4). At the base of each plate is a layer of wet blotting paper to simulate the sites of evaporation within the leaf.Since water vapor must diffuse from the sites of evaporation through the perforations in each plate, and...

show abstract

Measuring Transpiration Resistance of Leaves

Cited by 140 publications

References 6 publications

Seasonal Patterns of Acid Metabolism and Gas Exchange in Opuntia basilaris

Seasonal Patterns of Acid Metabolism and Gas Exchange in Opuntia basilaris

How Reliable Are Heat Pulse Velocity Methods for Estimating Tree Transpiration?

Leaf Temperature Effects on Measurements of Diffusive Resistance to Water Vapor Transfer

Contact Info

Product

Resources

About