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Transpiration

Transpiration is the evaporation of water from the leaves of plants. Water is lost from the leaf through special pores called stomata. Stomata are found onboth surfaces of the leaf but there are usually more on the ventral (lower surface ) of the leaf. This is to reduce the amount of transpiration that willoccur because the top of the leaf is exposed to more sunlight than the bottom.

http://education.uoit.ca/lordec/ID_LORDEC/transpiration_pull/

This interactive website explains transpiration pull. Plants use the process of transpiration pull to move water from the soil up into the leaves.

Heat from the environment causes the water in the sub-stomatal air spaces to evaporate out of the stomata. This process is called transpiration.

Transpiration is therefore defined as the loss of water vapour from the leaves of a plant.

Transpiration only occurs during the day when the stomata are open. At night the stomata are closed.

Excess water diffuses into the sub-stomatal air spaces to replace that which has been lost from the leaves

Water diffuses from the xylem of the leaf into surrounding mesophyll cells.

Water circulates to supply plants with their water requirements.

Water is pulled from the xylem of the stem to the xylem of the leaves. The xylem is found in the veins of the leaf.

Rate of transpiration

This increases in conditions of …

  • High light intensity (bright sunlight)
  • Increased temperatures (hot weather)
  • Wind
  • Low humidity (dry conditions)

Light Plants transpire more rapidly in the light than in the dark. This is largely because light stimulates the opening of the stomata. Light also speeds uptranspiration by warming the leaf.

Temperature Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises due to the increased kinetic energy ofthe water molecules. At 30°C, a leaf may transpire three times as fast as it does at 20°C.

Wind When there is no breeze, the air surrounding a leaf becomes increasingly humid thus reducing the rate of transpiration. When a breeze is present, the humidair is carried away and replaced by drier air. So a steep diffusion gradient is maintained.

Humidity The rate of diffusion of any substance increases as the difference in concentration of the substances in the two regions increases. When thesurrounding air is dry, diffusion of water out of the leaf goes on more rapidly.

Soil water A plant cannot continue to transpire rapidly if its water loss is not made up by replacement from the soil. When absorption of water by the roots fails to keepup with the rate of transpiration, loss of turgor occurs, and the stomata close. This immediately reduces the rate of transpiration (as well as of photosynthesis). If the loss of turgor extends tothe rest of the leaf and stem, the plant wilts.

The volume of water lost in transpiration can be very high. It has been estimated that over the growing season, one acre of corn (maize) plants maytranspire 1.5 million litres of water. As liquid water, this would cover the field with a lake 38 cm deep. An acre of forest probably does even better.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
why and for what was five kingdom of classification of organisms introduced
SUBHIKSHA Reply
give the ans as fast as possible
SUBHIKSHA
Comment on the ozone depletion over the period of 1982 to 1996
Mpho Reply

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Source:  OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
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