Plant Physiology: Xylem and Root Hairs
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Questions and Answers

What is the primary function of xylem in plants?

  • Storage of food
  • Transport of nutrients
  • Transport of water and dissolved mineral ions (correct)
  • Photosynthesis

Xylem cells are living cells that contain cell contents.

False (B)

What adaptation do xylem cells have that allows them to support plants?

Thickened outer walls with lignin

Root hair cells absorb water and minerals from the soil through ______.

<p>osmosis</p> Signup and view all the answers

Match the following functions with their corresponding structures:

<p>Xylem = Transports water and minerals Root Hair Cells = Absorbs water and minerals from soil Lignin = Strengthens xylem tubes Osmosis = Movement of water into root cells</p> Signup and view all the answers

What is the significance of root hairs in plants?

<p>They increase the surface area for absorption (B)</p> Signup and view all the answers

The process of mineral ion absorption by root hair cells occurs through osmosis.

<p>False (B)</p> Signup and view all the answers

What drives water entry into root hair cells?

<p>Higher water potential in the soil compared to the cell cytoplasm</p> Signup and view all the answers

What process causes water to pass into root hair cells?

<p>Osmosis (A)</p> Signup and view all the answers

Water moves through root cortex cells before entering the xylem.

<p>True (A)</p> Signup and view all the answers

What is the name of the vessels that carry water up to the leaves in plants?

<p>xylem</p> Signup and view all the answers

The pathway of water is: root hair cell → root cortex cells → ______ → leaf mesophyll cells.

<p>xylem</p> Signup and view all the answers

Match the following components with their roles:

<p>Root hair cells = Absorb water Xylem = Transport water Mesophyll cells = Perform photosynthesis Cortex cells = Facilitate water movement</p> Signup and view all the answers

What can be used to investigate water movement in plants?

<p>Food coloring (D)</p> Signup and view all the answers

A cross-section of the celery shows that all areas of the stalk are stained when dyed water is used.

<p>False (B)</p> Signup and view all the answers

What happens to the leaves of a celery plant in dyed water after a few hours?

<p>They turn the same color as the dyed water.</p> Signup and view all the answers

Which of the following factors affects the rate of transpiration?

<p>Temperature (A), Wind Speed (C)</p> Signup and view all the answers

High humidity decreases the rate of transpiration.

<p>True (A)</p> Signup and view all the answers

What happens to a plant when it wilts?

<p>The plant cells become deficient in water, leading to collapsed cell walls and inability to support itself.</p> Signup and view all the answers

When a plant wilts, it is because __________ water evaporates from its leaves than is available in the soil.

<p>more</p> Signup and view all the answers

Match the factors affecting transpiration with their effects:

<p>High Temperature = Increases transpiration rate High Wind Speed = Increases transpiration rate Low Humidity = Increases transpiration rate High Humidity = Decreases transpiration rate</p> Signup and view all the answers

What is the purpose of using heat in the process described?

<p>To cool the plant down by converting water into vapour (C)</p> Signup and view all the answers

Dry leaves will affect the transpiration rate results.

<p>True (A)</p> Signup and view all the answers

What should be done to the air bubble before recording the end location?

<p>The bubble should be reset by opening the tap below the reservoir.</p> Signup and view all the answers

Transpiration occurs faster when the ______ increases.

<p>wind speed</p> Signup and view all the answers

Match the following environmental factors with their effect on transpiration:

<p>Temperature = Increases transpiration rate Wind Speed = Increases evaporation Humidity = Decreases transpiration rate Light Intensity = Increases transpiration if sufficient</p> Signup and view all the answers

What is the first step in setting up the experiment for measuring transpiration?

<p>Cut a shoot underwater (C)</p> Signup and view all the answers

Changing multiple environmental factors at once is recommended during the experiment.

<p>False (B)</p> Signup and view all the answers

What should you do after allowing the plant to adapt to a new environment?

<p>Record the starting location of the air bubble.</p> Signup and view all the answers

What happens to the rate of transpiration as temperature increases?

<p>It increases (D)</p> Signup and view all the answers

Wind speed has no effect on the rate of transpiration.

<p>False (B)</p> Signup and view all the answers

What creates a continuous column of water in the transpiration stream?

<p>Cohesion</p> Signup and view all the answers

Transpiration produces a tension or ‘pull’ on the water in the xylem vessels that is created by the _____ of the leaves.

<p>evaporation</p> Signup and view all the answers

What role do stomata play in transpiration?

<p>They are the sites of gas exchange (D)</p> Signup and view all the answers

The many interconnecting air spaces between mesophyll cells help to create a large surface area for evaporation.

<p>True (A)</p> Signup and view all the answers

What is the primary pathway for water movement from roots to leaves in a plant?

<p>Xylem vessels</p> Signup and view all the answers

What is the main substance transported by phloem?

<p>Sugars and amino acids (B)</p> Signup and view all the answers

Phloem vessels are made of dead cells.

<p>False (B)</p> Signup and view all the answers

What is the process called when sucrose and amino acids are moved through the phloem?

<p>Translocation</p> Signup and view all the answers

During winter, the phloem may transport dissolved sucrose and amino acids from the __________ to other parts of the plant.

<p>storage organs</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Source = Where products of photosynthesis are produced Sink = Where products of photosynthesis are stored or used Sieve plates = Holes in phloem cell walls for transport Translocation = Movement of nutrients through phloem</p> Signup and view all the answers

Which part of the plant typically becomes the source during the summer?

<p>Leaves (A)</p> Signup and view all the answers

Phloem transport only occurs in one direction.

<p>False (B)</p> Signup and view all the answers

Name the two main substances that are primarily transported through the phloem.

<p>Sugars and amino acids</p> Signup and view all the answers

Flashcards

What is the function of xylem?

Xylem is a specialized plant tissue that transports water and dissolved minerals throughout the plant.

How are xylem cells connected?

Xylem cells are joined end-to-end, forming long, continuous tubes with no cross walls. This allows water to flow freely without interruption.

What is the state of xylem cells?

Xylem cells are dead, lacking cell contents. This allows water to pass through easily without obstruction.

What strengthens xylem cells?

The outer walls of xylem cells are strengthened with lignin, providing support to the plant. Lignin acts as a rigid scaffold, preventing the tubes from collapsing.

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What are root hairs?

Root hairs are microscopic extensions of root cells. They increase the surface area of the root, aiding in the absorption of water and mineral ions.

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How do root hairs absorb water?

Root hairs absorb water from the soil through a process called osmosis. This happens because the soil water has a higher water potential than the root hair cell.

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How do root hairs absorb mineral ions?

Root hairs absorb mineral ions from the soil through active transport. This requires energy because ions are moving against their concentration gradient.

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Why is the large surface area of root hairs important?

The large surface area of root hairs allows roots to rapidly absorb water and mineral ions from the soil, ensuring efficient supply to the rest of the plant.

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Transpiration

The process by which water evaporates from the leaves of plants, causing a loss of water vapor to the atmosphere.

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Xylem

The movement of water from the roots to the leaves of a plant.

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Transpiration Rate

The rate at which water is lost from a plant through transpiration.

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Temperature

The amount of heat energy present in a substance.

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Wind Speed

The movement of air.

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Light Intensity

The amount of light that falls on a surface.

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Investigating Transpiration Rate

An experiment designed to measure how a specific factor affects the transpiration rate of a plant.

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Cutting a Shoot Underwater

A technique used to prevent air from entering the xylem of a plant during an experiment.

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Water Pathway in Plants

The process by which water moves into root hair cells from the soil, then through the root cortex and eventually into the xylem vessels.

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Osmosis

The movement of water molecules from an area of high concentration to an area of low concentration through a semi-permeable membrane.

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Root Hair Cells

Specialized cells in the roots that increase the surface area for water absorption.

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Root Cortex

The layer of cells in the root that surrounds the vascular tissue.

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Mesophyll Cells

The cells that make up the main body of leaves and carry out photosynthesis.

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Investigating Water Movement

A method used to investigate the pathway of water through a plant by immersing a plant in a solution with a coloured dye.

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Xylem Vessels

Specialized tubes found in the stem of plants that carry the coloured dye from a solution to the leaves, proving the path water takes.

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Temperature and Transpiration

As temperature increases, the rate of transpiration increases.

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Wind Speed and Transpiration

As wind speed increases, the rate of transpiration increases.

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Transpiration Pull

The force that draws water up the xylem vessels due to the evaporation of water from leaves.

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Cohesion

The attraction between water molecules, causing them to stick together.

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Transpiration Stream

The continuous column of water moving up the xylem from roots to leaves.

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Stomata

The small openings on the underside of leaves that allow for gas exchange and water vapor release.

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Spongy Mesophyll

The cells responsible for gas exchange and water vapor release in leaves.

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Temperature Effect on Transpiration

High temperature increases the rate of transpiration because the water molecules have more energy to evaporate.

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Wind Speed Effect on Transpiration

High wind speed increases the rate of transpiration because it removes water vapor from the air around the leaves, allowing more evaporation to occur.

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Humidity Effect on Transpiration

High humidity decreases the rate of transpiration because there is more water vapor in the air, making it harder for the leaves to lose water.

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Wilting

A condition where plant cells lose water and become flaccid, causing the plant to droop and lose its structural support.

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What is translocation?

Transport of soluble products of photosynthesis (sugars and amino acids) from areas of production to areas of storage or use within a plant.

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Describe the structure of phloem tubes.

Phloem tubes are made up of living cells arranged end-to-end, with holes in the end cell walls called sieve plates. These holes allow for easy flow of substances.

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What determines the direction of translocation?

The direction of translocation can vary depending on the plant's stage of development and the time of year. However, the movement is always from the source (where the substances are made) to the sink (where they are stored or used).

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Explain how translocation changes throughout the year.

During winter, when leaves are absent, sucrose and amino acids may be transported from storage organs to other parts of the plant to support respiration. During the spring, storage organs serve as the source and growing areas become the sinks. In summer, leaves become the source as they produce sugars, and the roots become the sinks for storage.

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Compare and contrast xylem and phloem.

Phloem transports dissolved food, primarily sucrose and amino acids, while xylem transports water and dissolved minerals. The phloem consists of living cells while xylem consists of dead cells. Phloem has sieve plates that allow substances to flow freely, while xylem has no cell walls. Phloem transports in multiple directions, while xylem transports upwards.

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What is the main sugar transported in the phloem?

Sucrose is the primary sugar transported in the phloem. It is a disaccharide made of glucose and fructose, which are readily used by plant cells.

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What drives translocation in the phloem?

The transport of substances in the phloem is driven by a pressure gradient. The source has a higher hydrostatic pressure due to the loading of sugars, causing the flow towards the sink with lower pressure.

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How are sugars loaded into the phloem?

Active transport is involved in loading sugars into the phloem at the source. This process requires energy to move sugars against their concentration gradient, ensuring efficient transport.

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Study Notes

Transport in Plants

  • Xylem and Phloem: Plants contain two types of transport vessels: xylem and phloem.
  • Xylem Vessels: Transport water and minerals from the roots to the stem and leaves.
  • Phloem Vessels: Transport food materials (primarily sucrose and amino acids) made during photosynthesis from leaves to non-photosynthesizing parts of the plant. These are in vascular bundles throughout the plant.
  • Vascular Bundles: These bundles group the xylem and phloem together, which are arranged throughout the root, stem and leaves.

Xylem Function

  • Function: Transport tissue for water and dissolved mineral ions.
  • Adaptations:
    • Cells are joined end-to-end, with no cross walls, forming a long continuous tube.
    • The cells are essentially dead, without contents, allowing for efficient water transport.
    • Outer walls are thickened with lignin, providing strength and support to the plant.

Root Hair Cells

  • Structure: Extensions of epidermal cells in the root. Increase the surface area for absorption.
  • Function: Absorption of water and mineral ions from the soil primarily by osmosis. Active transport also plays a role.

Pathway Taken by Water

  • Process: Water moves from the soil, through the root hair cells, through the cortex cells, to the xylem vessels, and then to the leaves. This movement is primarily driven by osmosis.
  • Pathway: root hair cell → root cortex cells → xylem → leaf mesophyll cells

Investigating Water Movement

  • Method: A plant (like celery) is placed in a dyed water solution.
  • Observation: After a few hours, the leaves and stem will take on the color of the dye. This shows the pathway of water transport, indicating that xylem vessels transport the water through the plant. Specific dissection of celery cross-sections using a scalpel will easily isolate the xylem vessels.

Transpiration

  • Definition: Evaporation of water from plant leaves, followed by diffusion of water vapor through the stomata, which are typically on the underside of plant leaves to reduce water loss.
  • Xylem Adaptation: Xylem vessels are adapted in structure that facilitates upward movement of water against gravity. The hollow structure, lack of cell contents and reinforcing lignin support the column of water. Lignin reinforces walls to keep them stable and hollow for efficient water movement.
  • Mechanism: Cohesion and adhesion give water molecules the tendency to stick together and resist downward movement. Transpiration creates a tension, or pull, on water in the xylem, drawing water up the plant.

Explaining the effects of temperature, wind speed, and humidity

  • Temperature: Higher temperatures lead to faster transpiration rates due to increased evaporation.
  • Wind Speed: Higher wind speeds increase transpiration because they remove water vapor from around the leaf, increasing the concentration gradient for water loss.
  • Humidity: Higher humidity decreases transpiration because the air is already saturated with water vapor, lowering the concentration gradient.

Transpiration Stream (Extended)

  • Mechanism: Water molecules are drawn up the xylem by the transpiration pull. The cohesion of water molecules and adhesion of water (to the xylem cell walls) is crucial in this process, creating a continuous column against gravity.

Translocation (Extended)

  • Substance Transported (Sugars): Sugars (mainly sucrose) and amino acids manufactured during photosynthesis are carried around the plant in phloem. This movement is called translocation.
  • Direction: The direction can change in different stages of the plant's life cycle. It is generally from the source (where glucose is produced), to the sink (where it is stored or used).
  • Xylem vs Phloem: Xylem moves water in one direction, whereas translocation can work in all directions in the phloem.

Wilting

  • Cause: If water loss from leaves exceeds water uptake by the roots, the plant wilts due to reduced turgor pressure in the cells.

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Related Documents

Cambridge CIE IGCSE Biology PDF Transport in Plants

Description

This quiz explores the functions and adaptations of xylem and root hair cells in plants. It covers water and mineral absorption processes, as well as the significance of these structures in supporting plant life. Test your knowledge on how water moves through various plant parts!

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