Water Transport in Plants

Getting water to the leaves The leaves need the water to perform photosynthesis without water no photosynthesis. Without photosynthesis the plant will die. The leaves need the water to perform photosynthesis without water no photosynthesis. Without photosynthesis the plant will die. But the leaves can be hundreds of meters from the root where most of the water uptake occurs But the leaves can be hundreds of meters from the root where most of the water uptake occurs

Back to water properties Remember…….

Cohesion Cohesion = water molecules are attracted to other water molecules Cohesion = water molecules are attracted to other water molecules Due to Hydrogen Bonds – polarity of water molecule Due to Hydrogen Bonds – polarity of water molecule Could be broken by a surfactant - soap Could be broken by a surfactant - soap

Adhesion Water molecules attracted to other substances Water molecules attracted to other substances –Example glass

Root Pressure Dew occurs when the roots continue to take in mineral and the rate of transpiration is low Dew occurs when the roots continue to take in mineral and the rate of transpiration is low –When is transpiration low?

Root Pressure Pressure is created by the xylem Pressure is created by the xylem –Dissolved minerals are present in the root cells (get there from active transport) increases the solute concentration inside the cell, thus water enters through osmosis creating pressure forcing the fluid up the xylem –Thus, water is forced from the high pressure in the roots to the low pressure in the leaves. –Can only push water a maximum of a few meters

Transpiration What the plants over a few meters tall use to transport the water to the leaves What the plants over a few meters tall use to transport the water to the leaves Pulls the water up the stem Pulls the water up the stem Adhesion and cohesion help transpiration (which occur at the stomata and lenticels) sucks the water up the xylem Adhesion and cohesion help transpiration (which occur at the stomata and lenticels) sucks the water up the xylem

Transpiration As water is lost in the leaves and stem it must be replaced transpiration allows that to happen As water is lost in the leaves and stem it must be replaced transpiration allows that to happen Depends on temperature Depends on temperature –High temp = lots of transpiration water can raise 75cm per minute –Low temperature = transpiration rate slower

Sugar Transport Phloem moves the sugar from the leaves to the rest of the plant Phloem moves the sugar from the leaves to the rest of the plant Movement from source to sink Movement from source to sink Glucose moved by active transport into the phloem (via the companion cells) water enters by osmosis Glucose moved by active transport into the phloem (via the companion cells) water enters by osmosis Animation Animation Animation

Sugar Transport Increase water pressure pushes the water and sugar though the phloem to the rest of the plant -- pressure flow theory Increase water pressure pushes the water and sugar though the phloem to the rest of the plant -- pressure flow theory Sugars transported actively into the cells Sugars transported actively into the cells Water also leaves the cell Water also leaves the cell

Animation Links Transpiration Transpiration Transpiration