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Plant Transport

Xylem, phloem, transpiration

Two Transport Systems

Xylem: Transports WATER & MINERAL IONS upward (roots → leaves). Dead, lignified cells. No active transport.

Phloem: Transports GLUCOSE & AMINO ACIDS both UP & DOWN. Living sieve tubes + companion cells. Uses active transport.

Dead, empty cells: No cytoplasm, no nucleus. No maintenance cost.

Lignified walls: Thickened with lignin. Strong, rigid. Supports plant.

Transport: Water moves UP from roots to leaves. Mineral ions (nitrates, phosphates, potassium) also travel UP.

Movement driven by transpiration pull (water evaporation from leaves creates suction)

Living cells: Sieve tubes (transport) + companion cells (provide energy, ATP).

Sieve plates: Perforated walls between sieve tubes allow sap flow.

Transport: Glucose & amino acids move UP (from leaves to growing regions) & DOWN (from leaves to roots).

Movement requires active transport (uses ATP from companion cell mitochondria)

Evaporation of water from leaf surfaces through stomata

Process: Water in leaf cells → evaporates into air spaces → diffuses out through stomata

Purpose: Transports mineral ions UP xylem, cools leaf, maintains turgor

Note: Transpiration pull — water lost from leaves → pulls more water up xylem from roots (cohesion of water molecules)

Temperature: Higher temp → faster evaporation → higher transpiration

Humidity: Low humidity → steep concentration gradient → faster water loss → high transpiration

Wind: Carries away water-saturated air → steep gradient → high transpiration

Light: High light → stomata open → gas exchange → more water loss

Long hair-like projections: Increase surface area for water absorption

Thin walls: Allow osmosis (water moves from soil into cell)

High mitochondria density: Produce ATP for active transport of mineral ions (against gradient)

Water enters by osmosis (minerals accumulated inside), mineral ions by active transport

✓ Xylem = water UP (dead); phloem = glucose UP & DOWN (living)

✓ Transpiration pull moves water up xylem (cohesion)

✓ Four factors affect transpiration: temp, humidity, wind, light

✓ Root hair: large SA, thin walls, high mitochondria

✓ Phloem uses active transport (needs ATP); xylem passive

✅ Xylem: water + minerals UP (dead cells, transpiration pull)

✅ Phloem: glucose + amino acids UP & DOWN (living, active transport)

✅ Transpiration: water evaporation from leaves through stomata

✅ Factors: temperature, humidity, wind, light affect transpiration

✅ Root hair: large SA, thin walls, mitochondria-rich

Transport: moving resources through plants! 🌳💧