L3: Cell Wall, Growth, Plant Body Flashcards
Cellulose microfibrils made by _____________ in the plasma membrane
cellulose synthase enzymes
What are cellulose microfibrils trajectories determined by?
microtubules
How is cell enlargement achieved?
Increase in cell volume, increase protein synthesis, cell wall loosens to allow extension
Where does the secondary cell wall form?
formed internal to primary wall, external to the plasma membrane (not all plants form it)
primary cell wall
deposited during cell expansion
one layer with middle lamella with no lignin that is thin and flexible
hydrophilic
secondary cell wall
deposited after cell expansion completes
can be multiple layers with lignin present that is thick and rigid
more hydrophobic
what does alternating microfibril orientation in the secondary cell wall do
provides structural fortification; resists physical stresses from multiple directions
what does lignin do in the secondary cell wall?
provides mechanical strength and hydrophobicity; fortifies walls by filling space between cellulose microfibril bundles
lignin
amorphous, hydrophobic organic polymer that can be found in secondary plant cell walls
primary pit field
area of reduced primary cell wall, often penetrated by numerous plasmodesmata
pit
interruptions in a secondary cell wall
pit membrane
primary cell wall and middle lamella
transforming plasmodesmata into pits
when 2nd cell wall is deposited, it is not laid down over primary pit fields. Primary pit fields become pits, maintaining cell-cell continuity
pit examples
sclereids from pear fruit
in xylem vessel elements
must sense surroundings to _____ and _______
adapt growth, form defense
