CRSCI 3300 PART I

Module 1

More than 90%.

What percentage of water is present in growing plant cells?

transpiration cooling

as the water moves in the continuum, the nutrients from the soil are also absorbed by the plants and the normal plant temperature is maintained when the water vapor transpired from the leaves and considered as necessary evil

Photosynthesis, cell expansion, translocation, and transpiration cooling.

What are the four key roles of water in plants?

Passive and active uptake.

What are the two types of water uptake?

Passive doesn’t require energy (driven by water potential), active requires metabolic energy.

What is the main difference between passive and active water uptake?

Root hairs

What structure absorbs most water and nutrients?

Numerous fine root hairs

What increases the root’s surface area and penetration in soil?

Meristematic, elongation, maturation.

Name the three zones of root development.

Maturation zone.

In which zone do root hairs develop?

Apoplastic and symplastic.

What are the two main short-distance water pathways?

root hair to xylem

short distance of transport of water

root xylem to stem and leaves (fruits, seeds)

long distance transport of water

Casparian strip

What blocks the apoplastic pathway at the endodermis?

Cohesion-Tension Theory

What is the long-distance water transport theory in plants?

cohesion

binding of similar molecules

tension

the film of water in the xylem gets pulled up by the evaporative force or transpiration full known as __________

Transpiration pull and water cohesion via hydrogen bonds.

What drives water movement in the cohesion-tension theory?

Soil-Plant-Atmosphere Continuum

What is the SPAC in plant water movement?

Heat dissipation via water vapor loss from leaves.

What is transpiration cooling?

Ψw = Ψp (pressure potential) + Ψs (solute potential)

What is the equation for water potential (Ψw)?

It decreases (more negative)

What happens to water potential when solute concentration increases?

From high to low water potential

Which direction does water move?

Aquaporin

What protein facilitates active water uptake?

At night.

When does active uptake typically occur?

Accumulation of water (turgor pressure).

What causes cell enlargement in plants?

photolysis

Splitting of water using light during photosynthesis.

H⁺, O₂, and electrons.

What is released during photolysis?

NADPH and ATP

Products of the light reaction used in carbon fixation.

Less than 5%.

How much water is used for actual plant growth?

1 g of dry matter.

What does 500 g of water produce in plant dry matter (Taiz and Zeiger)?

Water movement in xylem and phloem.

What transports sugars and nutrients in plants?

Plant size, leaf surface area, growth duration.

Name three plant characteristics affecting water use.

C3 and C4

Which photosynthetic types use more water: C3/C4 or CAM like cactus

Hot, dry climates increase water use.

How does climate affect water use?

CROPWAT by FAO

What software estimates irrigation needs?

transpiration

Water loss from leaves via stomata.

gravitational water

Water that drains freely from soil

hygroscopic water

Water tightly bound to soil particles, unavailable to plants.

capillary water

Water held in micropores, available to plants.

hydrotropism

Root bending toward moisture.

ABA (abscisic acid).

What hormone is suspected to trigger hydrotropism?

Stage I: Normal
Stage II: Reduced growth
Stage III: Survival focus

three stages of soil dehydration?

Abscisic acid (ABA).

What hormone accumulates under drought?

cavitation

formation of air bubbles in xylem, reducing water transport.

Escape, Avoidance, Tolerance.

three drought adaptive mechanisms?

Drought avoidance

mechanism do cereals like rice mostly use

osmotic adjustment

Accumulation of solutes to retain water.

Deep roots, high stomatal resistance, high chlorophyll.

What traits help drought-tolerant rice?

Reproductive phase, especially spikelet fertility.

What is the most drought-sensitive stage in rice?

Water molecules

What replaces oxygen in soil during flooding?

Shifts to anaerobic (less efficient), producing ethanol and lactate.

What happens to respiration under flood stress

From 36 to 2 ATP.

How much does ATP production drop under anaerobic respiration?

N, P, K, Mg, Ca.

What nutrient deficiencies occur under flood?

Reactive Oxygen Species (ROS).

What increases under flood and causes damage?

Yellowing leaves, reduced growth, delayed flowering.

What are visible symptoms of flood stress?

aerenchyma

Air-filled tissue in roots helping O₂ transport.

adventitious roots

Roots formed above waterlogged zones to access air.

Ethylene

What hormone promotes adventitious roots?

lenticels

Stem/root pores that allow oxygen in.

Stem elongation to keep leaves above water.

What is the escape strategy in rice?

Suppression of growth to conserve energy under submergence.

What is the quiescence strategy in rice?

Bittersweet (Solanum dulcamara).

What plant is used as a model for flood tolerance studies?

Faster adventitious root formation.

What indicates flood tolerance in mungbean?

Declines due to reduced stomatal conductance and nutrient uptake.

What happens to photosynthesis under waterlogging?