Transport in Plants

Transport in Plants

• Plants have two types of transport vessels: xylem and phloem.
• Xylem transports water and minerals from roots to stems and leaves.
• Phloem transports food materials (mainly sucrose and amino acids) from photosynthesizing leaves to non-photosynthesizing regions in the roots and stem.
• Xylem and phloem are arranged in vascular bundles throughout the plant's root, stem, and leaves.

Xylem Tissue

• Xylem cells are arranged end-to-end, with no cross-walls, forming a tube.
• Xylem cells are dead, lacking internal contents, which allows water to move freely.
• The outer walls of xylem cells are thickened with lignin, strengthening the tubes and supporting the plant.

Root Hair Cells

• Root hairs are single-celled extensions of epidermis cells in the root.
• They grow between soil particles and absorb water and minerals.
• Water enters root hair cells by osmosis because soil water has a higher water potential than the cytoplasm of the root hair cell.
• The large surface area of root hairs increases the rate of water absorption.

Pathway Taken by Water

• Water moves from the root hair cells into the root cortex cells.
• Water moves through the root cortex and then into the xylem vessels.
• Osmosis causes water to move through these structures.

Investigating Water Movement

• The pathway can be investigated by placing a plant (like celery) in dyed water.
• After a few hours, the celery's leaves will turn the same color as the dyed water.
• This shows that water is transported through the plant via the xylem.

Transpiration

• Transpiration is the loss of water vapour from plant leaves.
• It occurs through stomata (small pores on the surface of leaves).
• Transpiration helps transport water and minerals to the leaves, and cools the leaves.
• Water loss from transpiration is replaced by water drawn up from the roots.

Transpiration Rate

• Factors that affect transpiration rate include temperature, wind speed, and humidity.
• Increased temperature, higher wind speed, and lower humidity increase transpiration rate.

Transpiration: Extended

• Water travels from the roots to the leaves via the xylem.
• Xylem vessels are made of dead cells with lignin to withstand pressure and provide structural support.
• The water rises due to the cohesive forces between water molecules (Cohesion-Tension Theory).
• This continuous column of water moves from the roots to the leaves. Water loss through transpiration is replaced through the roots by osmosis.

Translocation

• Translocation is the transport of sugars (mainly sucrose) and amino acids through the phloem.
• Phloem tissue is made of living cells that are joined end-to-end.
• Sieve plates (pores in cell walls) connect the cells, allowing sugars and amino acids to move freely.
• Sugars are transported from sources (like leaves) to sinks (like roots, stems, or fruits) where they are stored or used.

Investigating Transpiration Rate

• Students can investigate the effect of temperature, wind speed, and light intensity on transpiration rates by altering these conditions and observing the results.

Explore the fascinating mechanisms of how plants transport water, nutrients, and food through xylem and phloem. This quiz covers the structure and function of xylem tissue and root hair cells, essential for plant growth and health. Test your knowledge on these vital components of plant biology.