Plant Physiology: Root Pressure and Transpiration

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Questions and Answers

What is the primary cause of root pressure in plants?

Gravity pulling water downwards

Transpiration from leaves

Active mineral uptake and osmosis (correct)

Capillary action of the soil

In which scenario is root pressure most important for plant water transport?

During high transpiration rates

At night when transpiration is low (correct)

In dry soil conditions

When the plant is fully hydrated

How does active mineral uptake affect water potential in root cells?

It lowers the water potential, drawing water from the soil (correct)

It increases the water potential, allowing more water to enter

It has no effect on the water potential

It only impacts the upper sections of the plant

What role does root pressure play in tall plants compared to smaller plants?

It plays a minor role in both sizes but is vital for smaller plants Signup and view all the answers

What is the function of the xylem in water transport in plants?

To facilitate the upward movement of water and minerals Signup and view all the answers

Which process primarily contributes to the buildup of root pressure?

Osmosis following mineral uptake Signup and view all the answers

Which factor does NOT contribute to the Cohesion-Tension Theory of water movement in plants?

Root pressure generated by minerals Signup and view all the answers

What happens as water accumulates in the root xylem due to root pressure?

It generates positive pressure that pushes water upwards Signup and view all the answers

What is the primary role of transpiration in plants?

To pull water up from the roots Signup and view all the answers

Which structure is involved in the translocation of nutrients within plants?

Phloem tissue Signup and view all the answers

What mechanism drives the movement of sugars from the source to the sink in translocation?

Active transport and pressure difference Signup and view all the answers

What type of cells compose the phloem tissue?

Sieve tubes and companion cells Signup and view all the answers

Where does the active transport of sucrose typically occur in a plant?

In the leaves during photosynthesis Signup and view all the answers

Which statement correctly describes the concept of 'sink' in translocation?

The area where sugars are stored or used Signup and view all the answers

Which factor does NOT influence the rate of transpiration in plants?

Soil nutrient concentration Signup and view all the answers

In which direction can translocation occur within a plant?

In both directions, depending on the source and sink Signup and view all the answers

Study Notes

Root Pressure

Root pressure is the upward push of water from roots to the xylem.
It is caused by the active uptake of minerals by the roots, which lowers the water potential and draws water in by osmosis.
Root pressure is particularly important for smaller plants and maintaining hydration at night when transpiration is low.
It plays a minor role in taller plants.

Cohesion-Tension Theory

Water is pulled upwards in tall plants through the xylem due to cohesion, adhesion, and transpiration.
Cohesion: Water molecules are attracted to each other, forming a continuous column.
Adhesion: Water molecules are attracted to the xylem walls, further supporting the column.
Transpiration: The evaporation of water from leaves creates a negative pressure that pulls water up from the roots.

Transpiration

The process of water evaporation from the stomata on leaves.
Creates a tension (negative pressure) that pulls water up from the roots via the xylem.
Plays a major role in water transport in plants, especially during the day.

Translocation in Plants

The movement of sugars and amino acids through the phloem.
This process moves products of photosynthesis from source (production or storage) to sink (usage or storage).
Phloem: Composed of living sieve tubes and companion cells, which control and maintain the sieve tubes.
Source: Areas where sugars are produced (leaves) or stored (roots or tubers).
Sink: Areas where sugars are used (growing tips, flowers, fruits) or stored (roots).

Mechanism of Translocation

Sucrose is actively loaded into the phloem at the source, requiring energy (ATP).
Water follows via osmosis, increasing turgor pressure in the phloem.
This high pressure pushes the sugar solution towards areas of lower pressure (sink).
Sucrose is removed at the sink, lowering pressure and continuing the flow from source.

Bidirectional Flow

Translocation can occur in both directions, depending on the location of the source and sink.

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Description

This quiz covers key concepts in plant physiology, focusing on root pressure, cohesion-tension theory, and transpiration. Understand how these processes work together to maintain water movement in plants, especially in different environmental conditions. Test your knowledge on how smaller and taller plants manage hydration through these mechanisms.