Document page
biology 0610printed 101 · PDF 101
328 pagesrevision 46933
printed 101 · PDF 101
Page image rendered from the stored file at 110 dpi; it sharpens as you zoom. Outlines are placed from each region’s stored position on the page (612 × 792 pt).
readable
Source of this text: embedded text layer. The better of the embedded text and OCR is kept.
101
Through this way water from the top of the xylem vessel travels inside the leaf
through osmosis.
Through this way water pressure at the top of the xylem decreases. It is now
less than the pressure at the bottom of xylem vessels.
This pressure difference causes the water to flow upwards from area of high
pressure to area of low pressure
This difference in pressure is known as transpiration pull
Transpiration pull is a force produced by the difference in pressure.
Water molecules are also attracted to each other by cohesion. Adhesive forces
between water and cellulose also aids in transport up the stem.
This creates one transpiration stream up the xylem
Rate of transpiration can be measured through a potometer.
Conditions affecting transpiration rate
Transpiration happens faster when the the temperature is high
The higher the humidity, the lower the rate of transpiration.
The windy day, higher the rate of transpiration.
Translocation
The substances made in leaves are transported to other parts of the plant
where they are required. This is known as translocation.
The part of the plant from which a substance is being translocated is known as
the source.
The part of the plant where a substance is being translocated is known as
sink.