Detailed Notes on Water Movement and Transport in Fungi and Plants

Water can freely move in and out of cells based on their needs.
Non-carbon minerals and digestive enzymes play a key role in breaking down materials and facilitating uptake of monomers.

Fungi perform external digestion by secreting enzymes (proteases, cellulases, amylases) into the environment.
- These enzymes break down complex molecules into simpler monomers that can be absorbed.
Enzymes are synthesized in the endoplasmic reticulum (ER) and undergo processing in the Golgi apparatus before being secreted via vesicles.
This endomembrane system is efficient for producing and excreting large quantities of enzymes, making fungi useful in industrial applications.

Fungi transport nutrients, such as sugars, across their mycelium using turgor pressure generated from osmotic gradients.
Turgor pressure increases when solute concentration increases, causing water to enter cells (volume and pressure increase).
Septal pores between cells in a filamentous fungus allow for shared cytoplasmic contents, facilitating the transport of nutrients from source to sink.
Turgor pressure can effectively push materials through the fungal structure, enabling resource distribution for growth and energy utilization.

In a source region (e.g., where sugars are abundant), water enters cells, increasing turgor pressure.
In the sink regions (e.g., areas requiring glucose), pressure is lower (due to sugar utilization and reduced solute concentration).
This pressure gradient and concentration difference promote bulk flow of sugars from sources to sinks within the mycelium.

Plants also utilize turgor pressure to move resources (water and nutrients) throughout the plant body, especially between roots and shoots.

Plants consist of four major organs: roots, stems, leaves, and flowers, each containing three types of tissue: vascular, ground, and dermal.
Roots absorb water and non-carbon minerals from the soil, with root hairs increasing surface area for absorption.
The endodermis, containing a Casparian strip, regulates the entry of water and ions, ensuring selective absorption into the plant body.

Vascular tissue is essential for transporting water (via xylem) and sugars (via phloem) throughout the plant.
Xylem: Conducts water and minerals from roots to shoots; operates through cohesion and adhesion properties of water.
- Transpiration creates a negative pressure gradient that pulls water upwards.
Phloem: Moves sugars from source (e.g., leaves) to sink (growing regions or storage organs).
- Uses osmotic pressure to facilitate the movement of sugar and accompanying water, resulting in increased turgor pressure and bulk flow.

In leaves, water absorbed by roots is used in photosynthesis. During the day, stomata open to facilitate CO₂ entry for photosynthesis, leading to water loss due to evaporation.
As water evaporates from leaves, it establishes a pull that continues to draw water from the roots up through the xylem, maintaining a continuous flow.

Phloem cells require assistance from companion cells for metabolic functions because they lack certain organelles.
The sieve plates allow the free movement of sugars across phloem cells—maintaining a high concentration of sugar in source areas and lower concentrations in sink areas facilitates sugar movement through osmotic pressure and concentration gradients.