Botany Class 2

sieve cells

long, slender connecting cells in phloem
sieve tube elements are cells in angiosperms, sieve cell in gymnosperm
assoicated with specialized parenchyma cells called albuminous cells
usually not derived from the same cell by mitosis, but perform similar role as companion cell

sieve tube elements

found in phloem
aligned end to end into sieve tubes
associated with specialized parenchyma cells (nucleated companion cells)
derived from the same cell by mitosis and have numerous plasmodesmatal connections
both function together in phloem transport

sieve tube elements and companion cells

P-proteins staunch wounds
continuous wall called a sieve plate

Medullary rays

"pith rays"
composed primarily of parenchyma and transport for nutrients
for occlusion of xylem vessels
for deposition of terpenes in formation of heartwood

Vascular bundle:Eudicot

In secondary growth, the vascular cambium forms between the primary xylem and primary phloem and produces new xylem to the inside and new phloem to the outide

Protoxylem

the part of the primary xylem that differentiates early, while adjacent cells are still elongating

Phloem

Living vascular tissue that carries sugar and organic substances throughout a plant
produced in primary and secondary growth

Protophloem

The part of the primary phloem that differentiates early, while adjacent cells are still elongating during primary growth
often stretched and destroyed as part of expansion and elongation
analogous to protoxylem

Protophloem vs. protoxylem

both elongate, dead at maturity, heavily lignified, provide support but also conduct water and mineral nutrients inside the stem

companion cells

the active cells found next to sieve tube elements that supply the phloem vessels with all of their metabolic needs

where is protoxylem

Pectin

a soluble gelatinous polysaccharide that is present in ripe fruits and is extracted for use as a setting agent in jams and jellies

primary wall

alive during maturity

secondary wall

if lignified, dead a maturity
if not lignified, marenchyma, alive at maturity

Xylem froms and function

tracheary elements, tracheids, and
vessel elements- conduct/transport water and minerals
fibers- support and sometimes storage
parenchyma- storage

vessel elements

A short, wide, water conducting cell found in the xylem of most angiosperms and a few nonflowering vascular plants. Dead at maturity, vessel elements are aligned end to form micropipes called vessels.

Phloem form and function

sieve elements- long distance transport of food
Sieve and albuminous cells, sieve-tibe elements- materials and signaling molecules
Scelerenchyma, fibers, sclereids- support, sometimes storage
parenchyma-storage

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