chapter 9 - transport in plants

Dicots

plants that produce seeds containing 2 cotyledons, acting as food stores for the developing embryo, and forms the first leaves when the seed germinates

Vascular system

a system of transport vessels in animals or plants

Vascular bundles

the vascular system of herbaceous dicots, made up of xylem and phloem tissue

Xylem

plant transport tissue that carries water and minerals from the roots to the other parts of the plant

Parenchyma

storage and strengthening fibres

Lignin

strengthens the cell wall and is arranged in spirals for flexibility

Phloem

plant transport tissue that carries the products of photosynthesis to all cells of the plant

Sieve tube elements

The main cells of the phloem. They are elongated cells laid end-to-end with sieve plates between. They contain few organelles.

Sieve plates

The perforated end walls of sieve tube elements that allow plant assimilates to flow between cells

Companion cells

the active cells found next to sieve tube elements that supply the phloem vessels with their metabolic needs

Turgor

the pressure exerted by the cell surface membrane against the cell wall in a plant cell

Root hair cells

cells that have long hair like extensions that increase the surface area available for the absorption of water and minerals from the soil

Symplast

the continuous cytoplasm of living plant cells connected through the plasmodesmata

Symplast pathway

movement of water and solutes through the cytoplasm of the cells via plasmodesmata by diffusion

Apoplast

the cell walls and intercellular spaces of plant cells

Apoplast pathway

movement of substances through the cell walls and cell spaces by diffusion into cytoplasm by active transport

Endodermis

part of the root blocked by the casparian strip

Casparian strip

impermeable band of suberin that prevents harmful substances entering the xylem, and prevents leakage of water from xylem vessels

Root pressure

the active pumping of minerals into the xylem by root cells that produces a movement of water into the xylem by osmosis

Stomata

pores in the surface of a leaf or stem that may be opened and closed by guard cells

Guard cells

cells that can open and close the stomatal pores, controlling gaseous exchang and water loss in plants

Transpiration

the loss of water vapour from the stems and leaves of a plant due to evaporation from cell surfaces inside the leaf and diffusion down a concentration out through the stomata

Transpiration stream

the movement of water through a plant from the roots until it is lost by evaporation from the leaves

Cohesion tension theory

the best current model explaining the movement of water through a plant during transpiration

Source

regions of a plant that produce assimilates by photosynthesis or from storage materials

Sink

regions of a plant that require assimilates to supply their metabolic needs e.g. roots, fruits

Translocation

the movement of organic solutes around a plant in the phloem

Xerophytes

plants with adaptations that enable them to survive in dry habitats or habitats where water is in short supply in the environment

Hydrophytes

plants with adaptations that enable them to survive in very wet habitats or submerged at the surface of water