Facts about Transpiration - El Paso Community · PDF fileFacts about Transpiration: Water...
Transcript of Facts about Transpiration - El Paso Community · PDF fileFacts about Transpiration: Water...
Stages of Transpiration 1. Water uptake from soil. o Roots absorb water . o Water flows into root cells by osmosis. 2. Cohesion and adhesion to xylem. o Cohesion in xylem causes water to form a
continuous stream. (Brooker , et. al 2008)
o Water molecules carry a slight electric charge causing attraction which links molecules in long chains.
o Surface tension increases in the intercellular spaces of cells, pulling on water stream in xylem. (Brooker , et. al
2008)
3. Transpiration o Water is transported through xylem (long
continuous tubes). o Water escapes the leaves through microscopic pores
called stomata. o As each molecule breaks loose it pulls up another
molecule to create a continuous pulling tension all the way down the xylem to the root.
http://0-www.fofweb.com.lib.epcc.edu:80/activelink2.asp?ItemID=WE40&SID=5&iPin= WCR0766&SingleRecord=True.
XYLEM
•A plant vascular tissue that conducts
water, minerals, and organic
compounds. (Brooker, et. al 2008)
•Non-living tissues
•More than 90% of water transpired from
plants is lost through the stomata.
•Stomata closes to retain water.
•Stomata closes to allow entry of CO2 needed
for photosynthesis and to allow oxygen and
water vapor to exit.
(Brooker, et. al 2008)
Elizabeth Gallardo 2009
Water Potential and the leaf
Evaporation from the leaf sets up a water potential gradient
between the outside air and the leaf's air spaces. The gradient is
transmitted into the photosynthetic cells and on to the water-
filled xylem in the leaf vein. (Wallace) http://home.earthlink.net/~dayvdanls/plant_transport.html
Cross Section of oak Xylem
STOMATA
Facts about Transpiration: Water vapor from plant transpiration is an important source
of rainfall. (¾ of rainfall received by the Amazon tropical
rain forest comes from plant-transpired water vapor, it is
visible as a mist.) (Brooker, Widmaier, Graham, Stiling 2008)
It cools plant surfaces, local and global climate. (Brooker, e t. al 2008)
99% of water entering plants is lost as vapor during
transpiration. (Brooker, e t. al 2008)
A typical tree loses 400 L of water per day through
transpiration. (Brooker, e t. al 2008)
Transpiration is affected by heat:
The force can be so strong that on a hot day, when the
evaporation rate from the leaves is very high, water moves
through the plant at up to 30 inches (76 cm) a minute and
the sides of the xylem vessels are pulled in, making a
measurable difference in the diameter of the stem. (http://0-www.fofweb.com.lib.epcc.edu/activelink2.asp?ItemID=WE40&SID=5&iPin=EWCR0766&SingleRecord=True)
Stomata are small openings
found on the underside of
leaves that are connected to
vascular plant tissues. http://www.physicalgeography.net/fundamentals/8i.
html
Diagram abstracted from http://0-www.fofweb.com.lib.epcc.edu/Electronic_Images/Onfiles/SVRbio134.pdf
PHLOEM
•It is a specialized conducting tissue at the
center of the plant’s stem.
•Phloem loading-is the process of conveying
sugars to sieve-tube elements for long-distance
transport.
(Brooker, et. al 2008)
•Tall trees are able to transport water and
minerals to amazing heights and in some cases
more than 110 m.
•They are able to do this through an extensive,
branched, long-distance vascular system made
up of xylem and phloem tissues.
•Bulk flow-is the mass movement of liquid in
a plant caused by pressure, gravity, or both.
(Brooker, et. al 2008)
Phloem
BULK FLOW