lecture 13, Vasculature Flashcards
what two things make up the vascular system?
xylem and phloem
the body plan is composed of….(example from a generic angiosperm)
an apical-basal pattern, a radial pattern, and three tissue systems (epidermis, ground tissue, and vascular tissue)
what is the meristem?
a section of the plant where constant cell division occurs - a continuing source of new cells
what does the apical meristem give rise to?
protoderm, ground meristem, and procambium (the primary meristems)
what do the primary meristems give rise to?
primary tissues:
protoderm –> epidermis
ground meristem –> ground tissue
procambium –> primary xylem and primary phloem (vascular tissue system)
what is xylem and what is it responsible for?
water conducting cells, responsible for conduction of minerals and water, support, and food storage
primary xylem comes from…
procambium
secondary xylem comes from…
vascular cambium
what kind of growth do most plants exhibit?
primary growth
what plants exhibit secondary growth
gymnosperms and other woody plants
eg) conifers
what two lateral meristems are responsible for secondary growth
vascular cambium and cork cambium
what are the cell types in secondary xylem?
tracheids and vessel elements - both have secondary cell walls and lack protoplasts at maturity
what are the supporting tissues in secondary xylem?
fibers and parenchyma
how are tracheids made up?
made up into structures called pits. pits are thin modified primary cell walls. prevents air bubbles from forming
how are vessel elements made up?
made up of perforation plates, areas lacking primary and secondary cell wall. they are ladder-like scalariform or a single large opening
how does differentiation of a vessel element occur?
secondary cell wall thickens, primary cell wall at ends and disintegrates, cell undergoes apoptosis or programmed cell death
why are there both tracheids and vessel elements?
vessel elements are more vulnerable to air embolisms, a gas that has entered the vasculature and is obstructing water movement
what are fiber cells?
sclerenchyma cells which line the tracheary elements. contain no protoplast and are dead at maturity
how does water flow up the xylem?
via the cohesion/adhesion theory, water potential, and transpiration which is the driver of water flow
what is phloem necessary for?
sugars, amino acids, lipids, micronutrients, hormones, proteins, RNA, and signaling molecules
what are the 2 kinds of phloem?
protophloem and metaphloem
what are the 2 components of the phloem?
sieve elements (sieve cells and sieve tube-elements) and companion cells (assoicated with fibers and parenchyma)
what are sieve elements? what are the two types?
the principal conducting cells of phloem. they are a cluster of pores that join to adjacent cells.
sieve cells and
sieve tube elements (only in angiosperms)
what is the structure of sieve tube elements?
long vessels, sieve plates conspicuous at ends.
Contain a P-protein that forms a plug by the sieve plate. The “plug” is created to modulate traffic.
what is the P-protein?
known as Forisome, occur in some legumes and undergo rapid, reversible, calcium-controlled changes from condensed resting stage. in the dispersed state, they plug the sieve-plate pore, act as gate-keepers
what are companion cells?
specialized parenchyma cells, living i.e. has a nucleus.
Tightly associated with sieve-tube elements and deliver materials (molecules, proteins, ATP, etc.)
what does the mother of sieve-tube elements do?
forms sieve-tube element and companion cells. After division, P-protein bodies arise in cytoplasm
recap: xylem contains …. and phloem contains …. (what do they do?)
xylem contains:
tracheary elements (tracheids and vessele elements), fibers, and parenchyma
-tracheary elements: conduction of water and minerals
-fibers: support; sometimes storage
-parenchyma: storage
phloem contains:
sieve elements, sclerenchyma (fibers and sclereids), and parenchyma
-sieve elements: long-distance transport of food
-sclerenchyma: support; sometimes storage
-parenchyma: storage
