Plant Circulation and Transport

Vascular Tissues

plant tissues that are responsible for absorbing and transporting materials throughout the plant.

Xylem

a plant tissue that moves water and minerals from the roots to the rest of the plant. It also helps support the plant’s structure.

Phloem

a plant tissue that moves sugars and other nutrients from the roots to the stems and leaves. It also helps support the plant’s structure.

Xylem and Phloem Rays

special extensions of the vascular bundles that transport water or food laterally.

Primary Xylem or Primary Phloem

type of xylem or phloem that is formed early in development from apical meristems; involved primarily in transportation of water or nutrients.

Secondary Xylem or Secondary Phloem

type of xylem or phloem that is formed later in development from vascular cambia; involved primarily in structural support (but does perform some transportation of water or nutrients).

Tracheids and Vessel Elements

specialized cells of xylem that are involved in actual transportation of water and minerals.

Parenchyma Cells

type of cell found in xylem and phloem that is involved in storage of water or nutrients.

Xylem Fibers or Phloem Fibers

cells found in xylem or phloem that are involved in providing structural support.

Root Pressure

a mechanism involved in moving water upward in a plant; it involves pushing water up through the roots.

Cohesion-Tension Model

a mechanism involved in moving water upward in a plant; it involves the process of transpiration.

Transpiration

the evaporation of water from plant parts that are exposed to air; the process uses the energy from this evaporation to pull a water column upward in plant xylem.

Sieve-Tube Members

one of the cell types found in phloem; they perform the actual transportation of nutrients.

Companion Cells

one of the cell types in phloem; they lie adjacent to sieve tube members and nourish them.

Sieve Plates

the end portions of the cell walls of sieve tube members; they contain numerous pores through which nutrients must pass in order to be transported from one sieve

Sieve Tube

a long row or column of sieve tube members that are stacked sieve plate to sieve plate.

Phloem Sap

all of the materials in phloem mixed together; it is this sap that is actually transported in the phloem.

Sources

those areas of a plant where sugars and other organic substances are synthesized or stored.

Sinks

all other plant tissues that need and use the organic substances stored or synthesized at sources.

Translocation

process by which phloem sap moves from one sieve tube member to the next; it is accomplished through the fluid pressure

Fluid Pressure Flow Mechanism

Phloem sap moves from where it's made (sources) to where it's used or stored (sinks) because of water pressure differences in the plant's phloem tubes. Water from nearby xylem cells helps push the sap along by flowing in and out of the phloem.

Phloem loading

the active transport and accumulation of nutrients into the phloem sieve tubes at sources; it increases the pressure at the source end of the phloem sieve tubes.

Phloem Unloading

At the sink end of a plant, materials leave the phloem tubes. This lowers the sugar concentration and pressure inside the tube, helping the flow continue from source to sink.