B3.2 Transport (Plant)

xylem

vascular tissue that transports water and nutrients up from the roots

lignin

compelx polymer that provides rigidity to help the plant stand upright by embedding in the cell wall of xylem tubes

phloem

vascular tissue that transports carbohydrates, usually from the leaves to other parts of the plant

epidermis

prevents water loss and provides protection from microorganisms

cortex

unspecialised cell layer that sometimes stores food reserves

vascular bundle

contains multiple vessels of both xylem and phloem

sieve tube elements

form long tubes with sieve plates; lack a nucleus to reduce resistance flow

root pressure

positive pressure potential that can push water upwards against gravity

companion cells

provide ATP and proteins to maintain sieve tubes; connected by plasmodesmata

tracheids

elongated, lignified, dead xylem cells in vascular plants