Biology Lecture 9: Transpiration

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Questions and Answers

What is the primary function of transpiration in plants?

To regulate internal water levels (correct)

To increase photosynthesis rates

To protect against herbivores

To absorb nutrients from the soil

How does transpiration create a negative pressure in the leaf's vascular system?

By accumulating excess water

By increasing soil moisture

By promoting root growth

By losing water through stomata (correct)

What is guttation in the context of plant physiology?

Transfer of nutrients via xylem

Loss of water through stomata

Release of water droplets from leaves (correct)

Evaporation of water from roots

Which component of the plant controls the process of transpiration?

Stomata Signup and view all the answers

What does the loss of water through transpiration primarily drive?

Water uptake from the soil Signup and view all the answers

Which of the following factors influences the rate of transpiration?

Light intensity Signup and view all the answers

What distinguishes transpiration from evaporation?

Transpiration involves living cells Signup and view all the answers

What role do guard cells play in transpiration?

Opening and closing stomata Signup and view all the answers

Which type of plant is characterized by thriving in environments with moderate water availability?

Mesophytes Signup and view all the answers

What is cuticular transpiration?

Water lost through the cuticle on leaves and stems. Signup and view all the answers

How much water can a sunflower lose via transpiration in one day?

56 kg Signup and view all the answers

What characteristic is typical of xerophytes?

They survive in arid regions with limited water. Signup and view all the answers

Which statement best describes stomatal transpiration?

It occurs through stomata to facilitate gas exchange. Signup and view all the answers

What is one advantage of transpiration for plants?

It aids in the translocation of food. Signup and view all the answers

What does the term 'stoma' refer to in botanical terms?

An aperture bounded by guard cells Signup and view all the answers

Which type of plant typically has stomata present on both the upper and lower surfaces of leaves?

Mesophytes Signup and view all the answers

What characteristic defines anomocytic stomata?

Guard cells surrounded by irregular epidermal cells Signup and view all the answers

In which type of environmental conditions do xerophytes typically thrive?

Dry environments with limited water availability Signup and view all the answers

What distinguishes the stomatal distribution of xerophytes from mesophytes?

Xerophytes have stomata only on the lower surface Signup and view all the answers

Which plant family is often associated with anomocytic stomata?

Cucurbitaceae Signup and view all the answers

What is the primary function of guard cells in stomatal structure?

Controlling gas exchange Signup and view all the answers

What is a common characteristic of lenticular transpiration?

Involves gas exchange through woody structures Signup and view all the answers

What is the primary characteristic of tetracytic guard cells?

They are surrounded by four subsidiary cells. Signup and view all the answers

In which family is the actinocytic stomatal pattern typically observed?

Commelinaceae Signup and view all the answers

Which species is known for its kidney-shaped guard cells in the context of early stomatal studies?

Commelina communis Signup and view all the answers

What distinguishes the alternate pattern of guard cells?

They are surrounded by four or more subsidiary cells. Signup and view all the answers

Which of the following statements about subsidiary cells is correct?

Their arrangement can vary among different types of guard cells. Signup and view all the answers

What happens to guard cells during stomatal opening?

They expand due to increased turgidity. Signup and view all the answers

Which of the following triggers stomatal opening?

Increased sunlight and CO₂. Signup and view all the answers

What role do K⁺ ions play in stomatal movement?

They help guard cells become turgid during opening. Signup and view all the answers

What occurs during the closing of stomata?

Starch is formed and water potential becomes less negative. Signup and view all the answers

During which time do stomata typically open?

During the day. Signup and view all the answers

What process is primarily responsible for water entering guard cells?

Decreased water potential within the guard cells. Signup and view all the answers

Where does guttation occur in plants?

At hydathodes found on leaves. Signup and view all the answers

The closure of stomata due to ABA is primarily related to which condition?

Water stress or drought conditions. Signup and view all the answers

What type of subsidiary cell arrangement is seen in diacytic stomatal structures?

Perpendicular to guard cells Signup and view all the answers

Which family is an example of a plant with anisocytic stomatal structure?

Solanaceae Signup and view all the answers

What characterizes graminaceous stomatal structures?

Dumbbell-shaped guard cells Signup and view all the answers

Which of the following reports the occurrence of anisocytic stomata in 37 families?

Metcalfe & Chalk, 1950 Signup and view all the answers

What is a distinctive feature of subsidiary cells in paracytic stomata?

They lie parallel to the guard cells Signup and view all the answers

Which of the following examples belongs to the family Acanthaceae?

Nicotiana benthamiana Signup and view all the answers

What is the primary plant type associated with the Poaceae family?

Grasses Signup and view all the answers

Which stomatal type features guard cells surrounded by three unevenly sized subsidiary cells?

Anisocytic Signup and view all the answers

Study Notes

Lecture 9: Transpiration

Transpiration is the process by which water is lost from plants (aerial parts) to the atmosphere through stomata.
Water loss is crucial for water uptake.
Water loss creates a negative pressure (tension) in the leaf's vascular system, specifically in the xylem.
This tension pulls water up from the roots, through the stem, and into the leaves.

Advantages of Transpiration

Creates suction force for water conduction.
Aids in mineral absorption through root transpiration pull.
Evaporates excess water.
Maintains plant temperature.
Helps regulate opening/closing of stomata (pores).
Enables dispersal of excess energy from sunlight.

Types of Transpiration

Cuticular transpiration: Water loss through the cuticle (waxy layer) on leaves and stems. The cuticle helps reduce water loss.
Lenticular transpiration: Water loss occurs through lenticels, which are small, spongy openings in the bark of woody stems. Lenticels reduce water loss in stems and limit gas exchange.
Stomatal transpiration: Water loss through stomata (pores in leaves typically on the underside).

Stomatal Structure, Distribution, and Movement

Stomata are apertures in the epidermis, each bounded by two guard cells.
In Greek, stoma means “mouth,” and the term is often used with reference to the stomatal pore only.
Mesophytes: Stomata are typically present on both the upper and lower leaf surfaces. There are more stomata on the lower surface (abaxial) than the upper surface (adaxial).
Xerophytes: Stomata are typically found only on the lower leaf surface (abaxial) only.
Stomatal structure includes guard cells, pore, accessory cells, and cellulose microfibrils.
Stomatal movement (opening/closing) depends on guard cell turgidity.
Opening: Triggered by sunlight and CO2, photosynthesis begins, water potential becomes more negative, water diffuses into guard cells, and guard cells become turgid, stomata open.
Closing: Starch is formed, water potential is less negative, guard cells become flaccid and contract, and stomata close.
ABA closes stomata and Cytokinin opens stomata.
K+ ions are vital in stomatal opening/closing processes.

Guttation

Guttation is the exudation of water droplets from the tips or edges of leaves.
This process occurs through specialized structures called hydathodes, which are stoma-like pores typically located at the tips or edges of leaves and positioned above the ends of leaf veins.
Guttation happens during warm, humid nights when transpiration is low and root pressure forces water out through the hydathodes.
Guttation differs from transpiration as it occurs during night, involves liquid water, and contains dissolved substances. Transpiration takes place during the day, is in vapor form, and is pure water. Transpiration is controlled by stomata whereas Guttation is uncontrolled

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Description

This quiz covers key concepts related to transpiration in plants, including the process, advantages, and types of transpiration. Understand how water loss affects plant health, nutrient absorption, and temperature regulation through various mechanisms like cuticular and lenticular transpiration.