B4 - Phloem and Bark

identify the functions of phloem and what it transports and it’s direction.

transport tissue. cells are alive. transports photosynthate and nutrients. goes both up and down to growing points.

phloem structure

stucture is long, continuous root to tip. external to xylem.

phloem functions

it functions as a continuous highway for most materials. the external position means its not buried when xylem grows.

sugar source

part that makes or releases more stored sugar than it uses.

sugar sink

part that uses or stores more sugar than it makes.

how is photosynthate transported throughout plant

1) Sugar actively transported from source to phloem

2) H2O flows passively from the xylem into the phloem

3) H2O and sugar passively transported toward sink

4) Sugar actively transported into sink

understand the role of phloem in food chains

phloem feeding insects.

direct defense

plants produce physical barriers against insect herbivores, or compounds that exert repellent, antinutritive, or toxic effects

indirect defense

plants attract or nourish other organisms to reduce energy pressure.

outer bark

along stems and roots, all except tips

vascular cambium

secondary phloem and xylem are developed by vascular cambium.

cork cambium

develops outer bark

inner bark

layer of inner cells that transport nutrients from leaves to the rest of the tree

outer bark

protective layer of dead cells that protect the tree from defense.

identify three functions of outer bark for the plant

physical protection, photosynthesis, channel rain flow, not supporting parasites