This document discusses the movement of water at the tissue and organ level in plants. It describes how water is absorbed by roots through root hairs and mycorrhizal fungi, then passed through the root cortex to the stele via the apoplast or symplast pathways. The symplast involves movement through plasmodesmata connecting cell cytosols, while the apoplast involves movement through cell walls. Water then moves up through the xylem tracheids and vessel elements to the stem.

1. Movement of Water at the
Tissue/Organ Level
From Cell to Cell, Through the Root
to the Stem
Apoplast
Symplast

2. Water Absorption by Roots
• Surface is increased by:
– Root hairs
– Mycorrhizae - 90% of terrestrial plants
• Fungus attached to roots
– Hyphae form a mycelium
– Hyphae grow into the root , between plant’s cells

3. Apoplast Symplast
• Water and minerals are passed from the root
epidermis through the cortex to the stele via apoplast
or symplast

5. Water Movement Through Tissues
• Symplast – pathway through the cytosol of
adjacent cells via plasmodesmata
• Apoplast – water movement through the cell walls
• Transmembrane - slow

6. Symplast Pathway
• Central vacuole – stores water/minerals
– Tonoplast - membrane
• Proton pumps in the
tonoplast, pump H+ into the
vacuole
• Other active transport moves
soil minerals into the vacuole
(K+)
• Makes the cytosol hyposmotic
(increases Ψs )

7. Apoplast Pathway
• Materials flowing along the apoplastic route are
blocked by the waxy (suberin) Casparian strip at
the endoderm
• Must enter endodermal
cells to move into the xylem
– Enables endodermal cells
to extract (active transport)
minerals from soil

8. Movement Through Tissues
• Water passes through the cortex to the stele
(xylem – tracheids/vessel elements)