Ground Tissue -forms the bulk of the plant. -are hollow, nonliving support cells with secondary walls. -thin-walled and capable of photosynthesis when they contain chloroplasts. -have thicker walls for flexible support (celery strands).
Plant Ground Tissues SCLERENCHYMA • Thick cell wall • Strength and support • Thin cell wall • Storage & photosynthesis • Uneven cell wall • Flexible support PARENCHYMA COLLENCHYMA
Two Kinds of Plant Vascular Tissue - Vessel Elements- pitted cell wall. Water pipeline - Tracheids - pitted - Carries H2O, dissolved nutrients. • Xylem • Phloem - Upward movement. - Dead at maturity. - Carries products of photosynthsis. • Sieve tube -perforated end walls • - transport sugar • - Companion Cells- swirl cytoplasm to push sugar up or down - Up and downward movement. - Alive at maturity Sieve-tube Companion cells Vessels Tracheids
Vascular Tissue • Two types of vascular (transport) tissue: • Xylem transports water and minerals from roots to leaves and contains two types of conducting cells: tracheids and vessel elements. • Phloem transports organic nutrients from leaves to roots and has sieve-tube elements with companion cells, sieve plates.
Xylem structure Leaves Xylem transports water and minerals from roots to leaves Contains two types of conducting cells: tracheids and vessel elements. Water Roots
Tracheids lie along side other tracheids, over-lapping extensively, so that water can flow out of the pits of one cell into an adjacent cell. This allows long range transfer of water and solutes, although (since the cells are dead) the flow has to be passive, pulled by an external force. Water Flow (passive flow) The driving force for this flow is hydrostatic pressure, coming partly from root pressure (pushing up wards) but mainly from the suction pressure created by water being evaporated from leaves. Passive water flow in plants is upwards.
Softwoods (conifers) – tracheids only Hardwoods – note the larger bore of the vessel elements
In Angiosperms - Vessel elements, idealised Vessel element, here with a open end (simple perforation plate). A perforated (scalariform) perforation plate Tracheids
Leaves Organic nutrients Roots Phloem structure Transports organic nutrients from leaves to roots Has sieve-tube elements with companion cells cells at sieve plates.