Transport in Plants - Transpira�onTranspira�on is loss of water vapour from the leaves

Transpira�on

* Temperature* Rela�ve humidity* Wind speed

* Number and distribu�on of stomata* Percentage of open stomata* Water status of the plant* Structure of the canopy of the tree

Transpira�on drives Ascent of Sap which depends upon physical proper�es of water: * Cohesion * Adhesion * Surface tensionImportance of Transpira�on * Pulling ac�on helps in absorp�on and transporta�on of water * Cools leaf surface * Maintains turgidity of cells * Water supply for photosynthesis

Factors Affec�ng Stomatal Movement * Amount of light * Carbon dioxide concentra�on * Water supply

* Radially arranged microfibrils aid in stomatal opening* Turgidity regulates opening and closing of stomata* During the day, guard cells perform photosynthesis and this leads to an increase in osmo�c pressure* It absorbs water from adjacent cells, and becomes turgid* Outer walls of guard cells pushed outward and inner walls pulled inward which leads to opening of the stomata* During night, stomata remain closedInteres�ng Facts: * Transpira�on pull can create pressure sufficient to li� the water over 130 m high * C4 plants can reduce water loss due to transpira�on by maintaining CO2 level even a�er closing of stomata * The number of stomata is higher in lower surface of dorsiventral dicot leaf than the upper surface whereas, the numbers are equal in isobilateral monocot leaf

Cu�cular StomatalLen�cular

xylem

Environmental Factors Plant Factors

Factors Affec�ng Transpira�on

Structure and Mechanism of Stomatal Movement