- Absorption of water refers to the process by which plant roots take in water from the soil.
- Roots, particularly the root hairs, are crucial for water absorption.
- Absorption occurs through diffusion, where water moves from regions of higher concentration in the soil to lower concentration in the root cells.
- Thin-walled extensions of root epidermal cells that significantly increase the surface area for absorption.
- Root hairs absorb water along with mineral solutes purely through diffusion.
- The experiment with a twig in coloured water highlights the movement of water through vascular bundles, specifically the xylem.
- Understanding the mechanism of long-distance transport in plants is crucial for comprehending nutrient and water distribution.
- Diffusion is insufficient for long-distance transport due to its slow pace.
- Over short distances, diffusion is effective, but for extensive movements, additional mechanisms are required.
- The movement of a molecule across a typical plant cell takes about 2.5 seconds for a distance of 50 µm. Calculate the time required for a 1 m distance by diffusion alone.
- Water, minerals, and food are transported by mass or bulk flow systems.
- Mass flow involves substances moving en masse due to pressure differences, unlike diffusion where substances move independently.
- Bulk movement of substances through plant vascular tissues is termed translocation.
- Xylem and phloem are highly specialized vascular tissues associated with translocation.
- Xylem primarily translocates water, mineral salts, some organic nitrogen, and hormones from roots to aerial plant parts.
- Xylem ensures efficient upward movement of substances against gravity.
- Ascent of sap refers to the upward movement of water through the plant, particularly from the roots to the aerial parts.
- Phloem translocates a variety of organic and inorganic solutes, predominantly from leaves to other plant parts.
- Two-Way Transport: Phloem facilitates bidirectional movement, supporting the overall nutrient distribution.
- Vascular Tissue Specialization:
- Roots, Stems, and Leaves: Cross-sections reveal the specialized vascular system in higher plants.
- Xylem and Phloem: These tissues play distinct roles in nutrient and water transport.