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