Brandt semigroup: Difference between revisions

Revision as of 06:08, 13 January 2014

By definition, stomatal conductance, usually measured in mmol m⁻² s⁻¹, is the measure of the rate of passage of carbon dioxide (CO₂) entering, or water vapor exiting through the stomata of a leaf. Stomata are small pores on the top and bottom of a leaf that are responsible for taking in and expelling CO₂ and moisture from and to the outside air. The rate of stomatal conductance, or its inverse, stomatal resistance, is directly related to the boundary layer resistance of the leaf and the absolute concentration gradient of water vapor from the leaf to the atmosphere. It is under direct biological control of the leaf through the use of guard cells, which surround the stomatal pore ^[1] (Taiz/Zeiger 1991). Stomatal conductance is integral to leaf level calculations of transpiration (E).

Methods for Measuring

Stomatal conductance can be measured in several ways: Steady-state porometers: A steady state porometer, such as the SC-1 Leaf Porometer from Decagon Devices, Inc., measures stomatal conductance using a sensor head with a fixed diffusion path to the leaf. It measures the vapor concentration at two different locations in the diffusion path. It computes vapor flux from the vapor concentration measurements and the known conductance of the diffusion path using the following equation:^[2]

$\frac{C_{v L} - C_{v 1}}{R_{v s} + R_{1}} = \frac{C_{v 1} - C_{v 2}}{R_{2}}$

Where $C_{v L}$ is the vapor concentration at the leaf, $C_{v 1}$ and $C_{v 2}$ are the concentrations at the two sensor locations, $R_{v s}$ is the stomatal resistance, and $R_{1}$ and $R_{2}$ are the resistances at the two sensors. If the temperatures of the two sensors are the same, concentration can be replaced with relative humidity, giving

$R_{v s} = \frac{1 - h_{1}}{h_{2} - h_{1}} R_{2} - R_{1}$

Stomatal conductance is the reciprocal of resistance, therefore

$g_{v s} = \frac{1}{R_{v s}}$ .

A dynamic porometer, such as the Delta-T AP4, measures how long it takes for the humidity to rise from one specified value to another in an enclosed chamber clamped to a leaf. The resistance $R$ is then determined from the following equation:

$Δ t = \frac{(R + A) l Δ h}{1 - h}$

where ∆ $t$ is the time required for the cup humidity to change by ∆ $h$ , $h$ is the cup humidity, $l$ is the cup “length,” and $A$ is an offset constant.

Null balance porometers, such as the http://envsupport.licor.com/index.jsp?m=Discontinued&menu=Porometers&spec=LI-1600 LI-1600], from LI-COR, maintain a constant humidity in an enclosed chamber by regulating the flow of dry air through the chamber and find stomatal resistance from the following equation:

$R_{v s} = \frac{A}{f} (\frac{1}{h} - 1) - R_{v a}$

where $R_{v s}$ is the stomatal resistance, $R_{v a}$ is the boundary layer resistance, $A$ is the leaf area, $f$ is the flow rate of dry air, and $h$ is the chamber humidity.

The resistance values found by these equations are typically converted to conductance values.

References

↑ 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
↑ Template:Cite web

[1] 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.

My blog: http://www.primaboinca.com/view_profile.php?userid=5889534

[2] Template:Cite web

[1]

[2]

@@ Line 1: / Line 1: @@
+By definition, '''stomatal conductance''', usually measured in mmol m⁻² s⁻¹, is the measure of the rate of passage of carbon dioxide (CO<sub>2</sub>) entering, or water vapor exiting through the [[stoma]]ta of a leaf. Stomata are small pores on the top and bottom of a leaf that are responsible for taking in and expelling CO<sub>2</sub> and moisture from and to the outside air.
+The rate of stomatal conductance, or its inverse, stomatal resistance, is directly related to the boundary layer resistance of the leaf and the absolute concentration gradient of water vapor from the leaf to the atmosphere. It is under direct biological control of the leaf through the use of guard cells, which surround the stomatal pore <ref>{{cite book|last=Taiz/Zeiger|title=Plant Physiology|year=1991|publisher=The Benjamin/Cummings Publishing Company, Inc.|location=Redwood City, CA|isbn=0-8053-0245-X|pages=92–95}}</ref> (Taiz/Zeiger 1991).
+Stomatal conductance is integral to leaf level calculations of [[transpiration]] (E).
+==Methods for Measuring==
+Stomatal conductance can be measured in several ways:
+Steady-state porometers:
+A ''steady state porometer'', such as the [http://www.decagon.com/products/environmental-instruments/stomatal-conductance-porometry-instruments-2/sc-1-porometer-for-stomatal-conductance-measurements/ SC-1 Leaf Porometer] from Decagon Devices, Inc., measures stomatal conductance using a sensor head with a fixed diffusion path to the leaf. It measures the vapor concentration at two different locations in the diffusion path. It computes vapor flux from the vapor concentration measurements and the known conductance of the diffusion path using the following equation:<ref>{{cite web|title=First Look at Decagon's New Porometer|url=http://www.decagon.com/education/canopy-news-4/|work=Canopy News 2006|publisher=Decagon Devices, Inc.|accessdate=14 June 2011}}</ref>
-Have you been looking for more meaning in your life - a way of happiness? Have you been sick and tired of times that blend into each other? Can you get sitting in traffic feeling the warmth rising up your neck? Fighting with your family members, colleagues or neighbors? Have you been awakened night after night by the noise of the town? Perhaps it is time to get off it all: imagine a life where you could only get right up in the morning, stroll to the beach, have a fresh juice and take pleasure in the sun. <br><br>The truth is, if you should be feeling the work, it may be affecting your health: chronic stress could cause or worsen panic, depression, substance abuse, heartburn, chronic pain, high blood-pressure, ulcers the list continues. Many Americans have found a way to put all of this behind them. They have found a life where the pace of living is relaxed, and the worst day at the beach surpasses the greatest day in the office. <br><br>They&quot;ve found Costa Rica, land of "Pura Vida", take their time to enjoy it and where the residents enjoy life. Becoming more popular each year, this country is a lovely mix of local, United States, European and Argentinean cultures. The folks are generally friendly and laid-back. Dig up further on this partner site - Hit this URL: [http://www.fabula.org/atelier2/index.php/Costa_Rica_Real_Estate_Baby_Boom return to site]. [http://www.purevolume.com/touch25bus/posts/7908770/Have+a+Permanent+Vacation Account] is a offensive online library for more concerning why to do it. The price of living is 30 to 5-0 per cent lower than the worries levels and many American cities are considerably lower. <br><br>With a well-developed health care system, great public education, a well balanced political circumstance and clean drinking water, Costa Rica is a very modern country. In fact, Costa Rica was the very first nation to constitutionally abolish its military, disbanding it in 1948. It&quot;s also an environmentally fortunate country: Costa Rica includes six per cent of the world&quot;s biodiversity, and has 1-2 different climate zones to choose from. It is home to more than 850 species of birds, more than most of United States combined. <br><br>Owning property in Costa Rica is available to everyone foreigners have a legal and constitutional right to own property. In reality, should you not desire to live here regular it&quot;s not a challenge - there&quot;s no residency requirement. Whenever you like you can rent your home whenever you like, and sell. To research additional information, consider checking out: [http://www.cosmologyathome.org/team_display.php?teamid=7091 asesores en google ads]. Funding is quite easy to obtain and you will find no capital gains tax for the average property owner. While foreigners without a work permit are not permitted to work, it is possible to own a business here, or enjoy your retired life. Individuals who do earn income here will love the exceptionally low income tax. <br><br>So, in case you have ever dreamed of getting away from it all, Costa Rica could possibly be your answer. Time to make this dream a reality - It&quot;s simpler than you think: Costa Rica is truly the land of the dreams, and it is remarkably painless for Americans to make their property to this area..<br><br>In case you have almost any questions about in which and how you can employ physical health articles ([http://alertgovernor6461.blox.pl/html mouse click the next page]), you'll be able to call us in our web page.
+<math>\frac{C_{vL}-C_{v1}}{R_{vs}+R_1}=\frac{C_{v1}-C_{v2}}{R_2}</math>
+Where <math>C_{vL}</math> is the vapor concentration at the leaf, <math>C_{v1}</math>  and <math>C_{v2}</math>  are the concentrations at the two sensor locations, <math>R_{vs}</math> is the stomatal resistance, and <math>R_1</math> and <math>R_2</math> are the resistances at the two sensors. If the temperatures of the two sensors are the same, concentration can be replaced with relative humidity, giving
+<math>R_{vs}=\frac{1-h_1}{h_2-h_1}R_2-R_1</math>
+Stomatal conductance is the reciprocal of resistance, therefore
+<math>g_{vs}=\frac{1}{R_{vs}}</math> .
+A ''dynamic porometer'', such as the Delta-T AP4, measures how long it takes for the humidity to rise from one specified value to another in an enclosed chamber clamped to a leaf. The resistance <math>R</math> is then determined from the following equation:
+<math>\Delta t=\frac{\left(R+A\right)l\Delta h}{1-h}</math>
+where ∆<math>t</math> is the time required for the cup humidity to change by ∆<math>h</math> , <math>h</math> is the cup humidity, <math>l</math> is the cup “length,” and <math>A</math> is an offset constant.
+''Null balance porometers'', such as the http://envsupport.licor.com/index.jsp?m=Discontinued&menu=Porometers&spec=LI-1600 LI-1600], from [[LI-COR]], maintain a constant humidity in an enclosed chamber by regulating the flow of dry air through the chamber and find stomatal resistance from the following equation:
+<math>R_{vs}=\frac{A}{f}\left(\frac{1}{h}-1\right)-R_{va}</math>
+where <math>R_{vs}</math> is the stomatal resistance, <math>R_{va}</math> is the boundary layer resistance, <math>A</math> is the leaf area, <math>f</math> is the flow rate of dry air, and <math>h</math> is the chamber humidity.
+The resistance values found by these equations are typically converted to conductance values.
+===References===
+<references />
+[[Category:Plant physiology]]

Brandt semigroup: Difference between revisions

Revision as of 06:08, 13 January 2014

Methods for Measuring

References

Navigation menu

Search