2.3 : transport system in plants2.3 : transport system in plants! stomata in a leaf skin! • under...
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2.3 : Transport System in Plants Transpiration
• A process where plants release water into the air through their stems & leaves
• Stems have lenticels & leaves have stomata to transpire water
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Stomata in a Leaf Skin
• Epidermal cells on the leaf protect the cells underneath
• Stoma allows • Water to
escape from the leaf
• Gases to enter and exit from the leaf
• Guard cells control the size of the stoma openings Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Stomata in a Leaf Skin
• Under surface of a leaf has more stomata than the upper surface to avoid direct sunlight
• Most of the water absorbed by the roots are returned to the air through stomata during transpiration
Turgid Flaccid
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transpiration – HELPFUL EFFECT
• Cools the plant as heat is removed from the plant
• Gets rid of excess water from the plant
• As water is lost/used up, a pulling force is produced – water & minerals are sucked up from the roots, to the stem and leaves
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transpiration – HARMFUL EFFECT
• A plant will wilt if too much of water is lost
• Methods to reduce water loss: • Having hairs on
leaves (lalang) • Thick leaf skin
(rubber tree) • Rolling up leaves
on hot day (banana)
• Storing water in leaves (water lily)
• Having very small leaves (casuarina)
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Factors affecting Transpiration
Temperature
Humidity
Wind
Light
Surface of
leaves
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transport of Water and Food in a Plant
• The transport system in flowering plants transport mainly water containing dissolved mineral salts & food made during photosynthesis
• It consists of long thin vessels named xylem and phloem (extend from the roots to the leaves)
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transport of Water and Food in a Plant
• Xylem : carries water & mineral salts from roots to leaves
• Water enters the roots through osmosis – a process where weak solution (water in soil) moves into stronger solution (cell sap in the roots)
• Some of the water is used by the leaves while most of it is released through the leaves Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transport of Water and Food in a Plant
• In the stem, phloem is situated on the outer side of the xylem
• In the root, phloem alternates with the xylem
• Phloem carries dissolved food (sugar) from the leaves to all parts of the plant
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transport of Water and Food in a Plant
• Excess food is changed into starch & stored
• In the leaves, xylem and phloem are found in the veins
• The cambium makes new xylem & phloem for the plant.
Prepared by Ms Sue Soh Ya Lee
2.3 : Transport System in Plants Transport of Water and Food in a Plant
Prepared by Ms Sue Soh Ya Lee