plant phys midterm 1

all quizzes combined

What happens to a leaf cell’s turgor pressure as water potential becomes more negative during midday water stress?

Turgor decreases, leading to wilting

Which of the following describes osmotic adjustment?

Accumulating solutes to make Ψs more negative, maintaining water uptake

Why is osmotic adjustment important for growth and stomatal function?

It maintains turgor so stomata can remain partially open, allowing photosynthesis and cell expansion

What is a xylem embolism?

A conduit filled with air, blocking water transport

What is air seeding in xylem?

Air bubble pulled across pit membranes from an embolized conduit into a water-filled one

Which statement best represents the safety–efficiency trade-off?

Wide vessels in angiosperms transport water efficiently but are more vulnerable to embolism; tracheids in gymnosperms are narrower, less efficient, but safer.

Osmotic adjustment lowers osmotic potential (Ψs), allowing plants to maintain turgor and avoid wilting under drought stress.

True

Once a xylem conduit embolizes, water can bypass it through connections with neighboring conduits, but severe embolism spread can lead to plant death.

True

Which structures are found only in plant cells (not animal cells)?

Cell wall, chloroplast, vacuole

What molecule strengthens the secondary cell wall and allowed plants to grow tall on land?

Lignin

What is the main function of the middle lamella?

Cement that glues adjacent cells together

Which of the following best describes the function of chloroplasts?

Sites of photosynthesis

What is the main role of aquaporins in plant cells?

Allow rapid water transport across membranes

What do plasmodesmata allow plant cells to do?

Communicate and transport molecules between neighboring cells

Plant need to loose water to acquire CO₂ from the atmosphere for photosynthesis.

True

Around ___of water used by plants is lost to the atmosphere.

98%

Which feature distinguishes plant growth from animal development?

Plant growth depends strongly on environmental conditions

What are the three main phases of plant development?

Embryogenesis, vegetative, reproductive

Primary growth in plants is associated with:

Increase in height/length via apical meristems

Secondary growth in plants results in:

Thickening of stems and roots by lateral meristems

Lettuce bolting in the Salinas Valley is triggered primarily by:

Elevated temperatures and long days

What is the role of shoot apical meristems in plant growth?

They drive elongation and organ formation at stem tips

The shoot apical meristem (SAM) contains a central zone (slow division) and a peripheral zone (faster division for organ formation).

True

Blue light always promotes stem elongation in plants.

False

What is the primary role of transpiration in leaf temperature regulation?

Cooling of the leaf via evaporative water loss

Which instrument is commonly used to measure leaf water potential in the field?

Scholander pressure chamber (pressure bomb)

During the day, which gradient drives water movement through the plant?

Gradient of decreasing water potential from soil → roots → leaves → atmosphere

According to the cohesion-tension theory, what maintains continuous water columns in the xylem?

Cohesion among water molecules and adhesion to xylem walls

What happens to stomata as plants approach critical xylem tension values that risk cavitation?

They close partially to reduce transpiration

Root water uptake requires root water potential to be:

More negative than soil water potential

High temperature and low relative humidity increase atmospheric demand for water, thereby increasing transpiration rates.

True

Cavitation in xylem is a normal, routine process in well-watered plants.

False