Roots have to transportwater to the plant. Water acts as a solvent and reactant in cell metabolism

NECESSITY FOR TRANSPORT OF

SUBSTANCES IN PLANTS

Roots absorbed mineral salts and transported themto all parts of the plant.

Roots transport mineral ionsthat • required for chlorophyllsynthesis• for healthy plant growth• for development

Transport organic food materials from photosynthesis for :• energy requirement• growing regions• storage organ & other parts

VASCULAR TISSUE

consist of

Xylem Phloem

• transport water & mineral ions fromroots to the upper parts of plants.• give mechanical transport (xylem vessel)

• transport organic food substancesby the leaves during photosynthesis

consist

-Vessel : long, hollow, continuous tubes : strengthened by lignin deposited

in various patterns. : consist of dead cells : no protoplasm to obstruct the flow

of water.-Tracheids : less efficient in conducting water.

: don’t have open ends to form a continuous hollow tube.

-Parenchyma : consisting of roughly spherical, frequently with air spaces between them.

consist

-Sieve tube : a cylindrical tube consisting of elongated living sieve tube cells. : little cytoplasm, no nucleus : sieve plate with pores separating the sieve tube cell : allows the flow of dissolved food substances

-Companion : only found in flowering plantcells : adjacent and closely

associated with the sieve tube cells : has a nucleus, dense cytoplasm & many mitochondria : transport manufactured food(sucrose & amino acids) from the leaf cells

into the sieve tubes.

* In flowering plants

*

*#

*

# conifers and ferns

TRANSPORT OFSUBSTANCES IN PLANTS

TRANSLOCATION

• two directional transport, upwards or downwards of soluble food material by the phloem, from leaves to other parts.

• Importance :

- the survival of a plant ( sugars and amino acids are transported to growing regions for growth and development) - for metabolism of cells when the excess is stored in organs eg: …

TRANSPIRATION

• the loss of water in the form of water vapour from a plant to the atmosphere.• mostly lost through the stomata of leaves, small amount through the cuticle & lenticels in woody stems. (replaced?)

• Importance : - helps in the absorption & transport of… - water is used for photosynthesis & mineral salts for cell activities. - keep cells turgid to give support to leaves and young stems - keeps the plants cool in hot weather.

PATHWAY OF WATER FROM THE SOIL TO THE LEAVES

A) ROOT PRESSURE-Surrounding water soil is hypotonic to sap cell of root hair,Therefore water diffuse

into root hair by osmosis.The sap cell become hypotonic adjacent cell, then water moves again to the next

cell.Concentration gradient existed & & create a force call root pressure.

B) TRANSPIRATION PULLDuring the day, water evaporate from mesophyill cell into intercellularSpace in the leaves.From here water vapour diffuses to surrounding air through stomata callTranspiration & pull up water from the soil, the force is call transpiratianal

pull.

C) CAPILLARY ACTIONIs combine force of cohesion & adhesion which enable water move up

along the xylem vessel.Cohesion is the attraction of one molecule to other molecule of water.Adhesion is the attraction of water to the wall of xylem vessel.Therefore, xylem vessel forms a continuous column of water from root toStem & to the leaves.