BIOLOGY - PLANT TRANSPORT INTRODUCTION

Plants producing glucose from sunlight

Plants supplying energy

Required energy to move and transport substances

If water potential inside the cell is low (higher salt concentration) water will move in by osmosis. If water potential inside the cell is high (low salt concentration) water will move out by osmosis

In low external water potential, water moves out of the cell. Plants can survive this for short periods as they can shrink the cell membrane away from the cell wall. The cell is said to be plasmolysed.

Movement of water molecules and dissolved mineral ions. Xylem vessels and a passive process.

Movement of sugars (sucrose) and amino acids. Phloem vessel - sieve and companion cells and an active process

Extension of root epidermal cells to increase surface area - the more surface area there is, the more absorption there will be. Water and ions are absorbed mainly through root hair cells

Thin cellulose cell wall on root hair extension so distance for transport is short. Large numbers of root hairs each with a long and thin extension into soil to increase the surface area for absorption. Large number of ATP to produce ATP for active transport of ions.

Absorbed passively into cell wall which acts as a sponge and can move into the cell cytoplasm through osmosis

Passively with water into the cell wall and by active transport into the cell cytoplasm

Presence of root hairs for the uptake of water and mineral ions. Epidermal cells protect roots as they grow through the soil

Can act as a storage organ. Intercellular spaces allow movement of water and ions

Waterproof layer that forces water and ions into the cytoplasm of the endodermal cells and controls transport into the xylem.

Has a role in controlling transport into the xylem. Site of lateral root growth

Transports water and ions from the roots to the stem and leaves. Provides support for the plant

Transports products of photosynthesis to the roots from the leaves

Meristematic tissue that can undergo mitosis to produce more xylem and phloem

Apoplastic, symplastic and vacuolar

Water that has soaked into the cellulose cell wall can move from cell to cell by diffusion through the cell walls. Cell walls act as a sponge. This is a passive movement and water moves by cohesion. This is fastest route of transport across the cortex - there is less resistance as there are no membranes to cross and the cellulose cell wall is fully permeable to water

Endodermis is home to the casparian strip, which is impermeable layer of suberin, and as a result all water in the apoplast pathway is forced into symplast pathways

Water can move into the cytoplasm of the root hair cells by osmosis. Movement of water can then take place passively through the cytoplasm and between cells through the plasmodesmata

Water can also move between the cytoplasm and the large central vacuole -movement between cells is via plasmodesmata. The vacuolar route is the slowest route for transport across the cortex. Each time water has to cross membranes, there is resistance to movement and the speed of transport decreases

Concentration of available ions in soil is usually lower than inside plant cells, lowering the water potential in the roots so that water enters epidermal cells by osmosis

Salts are actively pumped into vascular tissue from the endodermal cells. Water potential of xylem is more negative and water enters the xylem by osmosis. Water potential gradient set up creates a force known as root pressure