Chapter 8) Transport in plants

Transport in plants

movement of water, mineral ions and sugars through a plant

Xylem

tissue that transports water and mineral ions from roots to leaves and provides support

Phloem

tissue that transports sugars (sucrose) and amino acids around the plant

Transpiration

loss of water vapour from leaves through stomata by evaporation and diffusion

Transpiration stream

continuous flow of water from roots to leaves through xylem

Water uptake

absorption of water by root hair cells by osmosis

Mineral ion uptake

absorption of mineral ions by active transport

Root hair cell

specialised cell with large surface area for absorption of water and mineral ions

Osmosis

movement of water through a partially permeable membrane from high water concentration to low water concentration

Active transport

movement of substances against a concentration gradient using energy (ATP)

Cohesion

attraction between water molecules

Adhesion

attraction between water molecules and xylem walls

Capillarity

movement of water in narrow tubes due to cohesion and adhesion

Transpiration pull

upward pull of water caused by evaporation at the leaves

Evaporation

liquid water turning into water vapour

Diffusion

movement of particles from high to low concentration

Stomata

pores in leaves where gas exchange and transpiration occur

Guard cells

cells that control opening and closing of stomata

Turgid

guard cells swollen with water, stomata open

Flaccid

guard cells lacking water, stomata closed

Factors affecting transpiration

light intensity, temperature, humidity, wind speed

Light intensity

increases transpiration as stomata open

Temperature

increases rate of evaporation and diffusion

Humidity

higher humidity reduces transpiration

Wind speed

increases transpiration by removing water vapour

Potometer

apparatus used to measure rate of water uptake (estimate of transpiration rate)

Translocation

movement of sucrose and amino acids in phloem

Source

part of plant where sugars are made (e.g. leaves)

Sink

part of plant where sugars are used or stored (e.g. roots, fruits)

Bidirectional flow

movement in phloem can go in both directions

Support

xylem walls are thickened with lignin to provide strength

Lignin

substance that strengthens xylem vessels