Plant Biology: Auxins and Water Regulation

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What role does auxin play in cell elongation?

It decreases the availability of polysaccharides in the cell wall.

It binds to receptors and enhances cell wall rigidity.

It activates the H+ pump, leading to increased acidity in the cell wall. (correct)

It increases proton pump activity, facilitating proton influx. (correct)

Which statement accurately describes the Acid Growth Hypothesis?

It suggests that auxin has no effect on the cell's proton pump activity.

The hypothesis proposes that increased acidity leads to increased wall extensibility. (correct)

Acidic conditions inhibit cell elongation by reinforcing the cell wall.

Incubation of auxin promotes cross-linking of cellulose fibers.

What effect does the binding of auxin to its receptor have on the cell's internal processes?

It enhances the cross-linking of polysaccharides in the cell wall.

It removes inhibition of phosphatase activity. (correct)

It leads to the repression of expansin production.

It suppresses proton pump activity.

How does auxin influence the direction of its effects in plant cells?

Based on the light direction affecting its distribution. Signup and view all the answers

What is the role of expansin in relation to the cell wall?

It aids in the loosening of the cell wall, enabling elongation. Signup and view all the answers

What is the primary driving force for water movement in plants?

Pressure potential Signup and view all the answers

How do guard cells respond to blue light?

By activating water uptake processes Signup and view all the answers

Which component is crucial for the signal transduction in response to light in guard cells?

A+ pump Signup and view all the answers

What happens to the water potential (YS) in plant cells when solute concentration increases?

YS decreases Signup and view all the answers

What role does transpiration play in water management for plants?

Regulates stomatal opening Signup and view all the answers

Which factor primarily determines the amount of water available to plants?

Soil moisture content Signup and view all the answers

What is the overall effect of root water uptake on plant growth?

Facilitates nutrient transport Signup and view all the answers

What signal do guard cells respond to for regulating stomatal aperture?

Light signals Signup and view all the answers

What role does the proton pump play in plant elongation?

It generates a proton gradient for the activity of auxin. Signup and view all the answers

How does auxin influence the activity of the proton pump?

Auxin increases the activity of the proton pump. Signup and view all the answers

What effect does the increased proton export have on the plant cell walls?

It activates expansins to loosen cellulose connections. Signup and view all the answers

What is the primary source of energy for the proton pump's function?

ATP produced during cellular respiration. Signup and view all the answers

What effect does generating a more negative membrane potential have?

It generates a gradient that favors proton movement. Signup and view all the answers

In what way does the apoplast differ from the symplast in plant tissue?

Apoplast allows for bulk flow of water and solutes. Signup and view all the answers

Which ions are actively co-transported with protons in plant cells?

Cations and anions are both co-transported. Signup and view all the answers

What is the functional consequence of high H+ concentration in the cytoplasm?

It allows for higher turgor pressure in cells. Signup and view all the answers

What is the primary function of auxin in plant cells?

To induce cell elongation Signup and view all the answers

How do plants primarily sense light direction?

Via phototropins Signup and view all the answers

What effect does light have on stomata?

Stomata open due to increased water pressure Signup and view all the answers

Where do PIN proteins primarily localize in plant cells during phototropism?

To the bottom of the cells Signup and view all the answers

What causes auxin to accumulate more on the shaded side of a plant?

Phototropins activation Signup and view all the answers

What defines the role of phytochrome in plant growth?

It regulates stem elongation based on light Signup and view all the answers

Which component is responsible for regulating the movement of auxin through plant cells?

Auxin co-transporters Signup and view all the answers

What triggers the opening of stomata in response to light?

Increased water potential Signup and view all the answers

What is the primary role of guard cells in plants?

Regulating water loss Signup and view all the answers

Which hormone primarily influences plant cell elongation?

Auxin Signup and view all the answers

What is the main effect of high red to far-red ratios in plants?

Canopy elongation Signup and view all the answers

What is the role of aquaporins in plant cells?

Facilitating water transport Signup and view all the answers

What happens to PIN proteins when the plant is exposed to low red to far-red light ratios?

They move to the sides Signup and view all the answers

What physiological characteristic of guard cells allows them to control stomatal opening?

Thick cell walls Signup and view all the answers

What primarily drives the movement of water from the roots to the leaves in plants?

Transpiration rate Signup and view all the answers

Which factor influences the water potential gradient in plants?

Transpiration rate Signup and view all the answers

How does the water content in the soil affect xylem water flux?

Higher soil water content increases xylem pressure. Signup and view all the answers

What role do stomata play in water movement within a plant?

They allow water vapor to exit the leaf. Signup and view all the answers

What condition is indicated by a negative water potential in the xylem?

Strong tension from transpiration Signup and view all the answers

In which part of the plant does the majority of transpiration occur?

Leaves Signup and view all the answers

What effect does high relative humidity (RH) have on transpiration?

Decreases transpiration rate Signup and view all the answers

Which of the following components is NOT a primary factor in the xylem's water transport mechanism?

Phloem function Signup and view all the answers

What is the primary cause of the negative pressure potential in the xylem according to the cohesion-tension hypothesis?

Water evaporation from stomata Signup and view all the answers

What is the role of guard cells in stomatal function?

They prevent water loss by regulating stomatal opening. Signup and view all the answers

Which condition would stimulate the opening of stomata in guard cells?

Accumulation of solutes inside guard cells Signup and view all the answers

What triggers the production of ABA in plants?

Nighttime or water stress conditions Signup and view all the answers

How does water adhesion affect the movement of water in plants?

It helps water molecules stick to plant surfaces. Signup and view all the answers

Which process is primarily responsible for creating tension in the xylem?

Evaporation from leaves Signup and view all the answers

How does the turgor pressure in guard cells affect stomatal opening?

Higher turgor pressure opens stomata. Signup and view all the answers

What is the effect of solutes being pumped out of guard cells during stomatal closure?

Decreases turgor pressure in guard cells Signup and view all the answers

What role does surface tension play in the movement of water in plants?

It helps resist the curvature of water in the xylem. Signup and view all the answers

Which component is NOT directly involved in gas exchange in leaves?

Phloem Signup and view all the answers

Study Notes

Plant Growth and Mass Balance

Plants use photosynthesis to create biomass and cellular respiration releases energy from storing materials.
Plant cells actively transport auxin, through co-transporters. This dictates the amount of auxin in each cell.
Auxin movement is significant in plant cell elongation. Auxin travels through PIN proteins to effect changes in elongation.

Plant Elongation

Water uptake plays a key role in plant cell elongation.
Plants sense light directionally, using phototropins which are membrane-bound proteins.
Phototropin (PHOT) proteins in plants absorb blue light. They become phosphorylated on one side of the cell (dependent on light direction), generating a signal to move auxin away from light.

Shade Avoidance Response

Phytochrome is a photoreceptor involved in shade avoidance. There are two forms: Pr and Pfr.
Pr absorbs red light, causing conversion to Pfr.
Pfr moves to the nucleus, to signal genes to change expression.
Changes in the phytochrome conformation alter the shape, triggering downstream responses.
The balance between red and far-red light influences gene expression relevant to growth and development.

Acid Growth Hypothesis

Auxin increases proton pump activity in the cell membrane.
Proton pumps transport hydrogen ions (H+) into the cell wall.
The acidic environment weakens cell wall connections allowing for expansion and growth.
Hydrogen ions increase the extensibility of the cell wall, enabling plant cell elongation.

Water Potential

Water potential (Ψ) reflects the tendency of water to move from one region to another. It is a measure of water's free energy.
Water potential is affected by solute potential (Ψs) and pressure potential (Ψp).
Solute potential is a measure of the effect on water potential by solutes dissolved in water. Adding solutes lowers the water potential.
Pressure potential is a measure of the effect of pressure on water potential. Applying pressure increases water potential.
Water moves from a region of high water potential to one of low water potential. This is crucial for water uptake.

Stomata

Stomata are pores in leaves that regulate gas exchange (CO2 intake, water loss).
Guard cells control the opening and closing of stomata.
Blue light triggers guard cell opening by increasing potassium (K+) ions and hydrogen ions.
Water movement into guard cells increases turgor pressure, opening the pores.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the crucial roles of auxins in plant cell elongation and the water management processes in plants. This quiz covers topics like the Acid Growth Hypothesis, guard cell responses, and the effects of transpiration on plant growth. Test your understanding of how these factors contribute to plant biology.