Plant Biology: Water Transport, Transpiration & Stomatal Regulation

What is the primary function of roots in water absorption?

Roots absorb water, but most is lost through transpiration in shoots.

What percentage of water absorbed by roots is typically lost through transpiration?

~95%

What is transpiration?

The process where water evaporates from the leaf air spaces through stomata into the atmosphere.

How does water potential affect water movement in plants?

Water moves from regions of high water potential to regions of low water potential.

What is the transpiration-cohesion-tension model?

It describes how water is pulled up through plants due to transpiration, cohesion, and tension.

What are the two types of xylem cells involved in water movement?

Tracheids and vessel elements.

What are tracheids?

Long and thin xylem cells that overlap and allow slow water flow.

What are vessel elements?

Shorter and wider xylem cells that allow faster water movement.

What role do stomata play in plant water regulation?

Stomata open for CO2 intake and close to prevent excessive water loss.

How do environmental factors influence stomatal behavior?

Water availability, humidity, temperature, and light intensity affect stomatal opening and closing.

What happens to stomata when water is scarce?

Stomata close due to increased production of abscisic acid.

What is the effect of high humidity on transpiration?

High humidity reduces transpiration rates.

How does light intensity affect stomatal behavior?

Light usually causes stomata to open in the morning and close in the afternoon.

What adaptations do plants have to reduce transpiration?

Leaf position changes, stomatal cycling, thicker cuticles, and sunken stomata.

What is the role of potassium ions in guard cells?

Increased potassium draws water in, causing guard cells to swell and open stomata.

What is the significance of the cuticle in plants?

The cuticle retains water, helping to reduce water loss.

What is the maximum height water can theoretically move in trees?

~150 meters.

What happens to transpiration when water loss exceeds uptake?

Transpiration leads to a loss of water pressure, causing stomata to close.

What is the relationship between transpiration and photosynthesis?

Transpiration is necessary for photosynthesis, but excessive loss can halt it.

How do trichomes help in reducing transpiration?

Trichomes reflect light and help keep leaf temperature down.

What is the role of leaf abscission in water conservation?

Dropping leaves reduces transpiration when water is limited.