Plant Anatomy: Phloem Fibers and Vascular Bundles

Study Notes

Made up of sclerenchymatous cells, generally absent in primary phloem but found in secondary phloem
Cell wall is thick, and at maturity, they lose their protoplasm and become dead
Function as strengthening and supporting cells

Consist of xylem and phloem, which together constitute vascular bundles
Three types of vascular bundles:
- Collateral vascular bundles: have xylem and phloem arranged adjacent to each other, found in dicotyledonous stems and monocotyledonous leaves and stems
- Radial vascular bundles: have xylem and phloem arranged in an alternate manner along different radii, found in roots
- Concentric vascular bundles: have xylem and phloem jointly situated along the same radius, found in stems and leaves

Living cells, only living component found in xylem tissue
Thin-walled, made up of cellulose, and store food materials such as starch or fat

Complex tissue composed of several cell types, including sieve tubes, sieve cells, companion cells, phloem fibers, and phloem parenchyma
Functions to conduct dissolved food materials (primarily sugars) produced by photosynthesis throughout the plant

Can be segregated into sieve tubes or sieve cells
Sieve tubes are more specialized, consisting of long, tube-like structures arranged longitudinally and laid end to end, forming sieve tubes
Sieve cells are less specialized

Important component of the "plumbing" and storage systems of a plant
Chief conducting tissue throughout all organs for water and minerals absorbed by the roots
Two types of xylem tissue: primary xylem and secondary xylem
Primary xylem develops earlier and is first formed from procambium of apical meristem, while secondary xylem develops from vascular cambium
Primary xylem consists of protoxylem and metaxylem, with protoxylem containing few tracheary elements (tracheids or vessel)