L11 - cell walls 2

secondary cell walls can have various configurations depending on -

secondary cell walls can have various configurations depending on -

cell type

cross section of sclereid fiber cells allow for -

support

lignin is a - polymer built from -

• cells secrete monolignol glucosides into -

• glucoside removed by -

• monolignol polymerization occurs

phenolic, monolignols, cell wall space, glucosidase

as lignin forms, it displaces - and forms a - network

• covalently linked to - and other -

water, hydrophobic, cellulose, polysaccharides

lignin is -, preventing collapse when there is - in xylem

strong, tension

lignin is resistant to enzyme and microbe -

degradation

monolignols polymerize into structurally - lignin polymers within the -

variable, cell wall

casparian strips are formed by - polymerization lignin, which is organized by -

localized, membrane-bound enzymes

top arrow? bottom arrow?

exodermis, endodermis

what are two consequences of lignification that are essential for water transport?

makes cells

1. waterproof

2. rigid

wall expansion can be - or -

highly localized, evenly distributed

highly localized wall expansion can be found with -

tip growth

highly localized wall expansion can occur in - (four things)

cotton fibers, pollen tubes, wood fibers, and root hairs

evenly distributed wall expansion can be found with -

diffuse growth

microfibril orientation directs -

cell expansion

new cells tend to be -, meaning - diameter in all direction

isodiametric, same

anisotropic orientation are when - are oriented in a - direction

microfibrils, particular

when microfibrils are in anisotropic orientation the microfibrils will only allow expansion - to their orientation

perpendicular

the multinet growth hypothesis: only the most - layer is well organized and the most recently formed layer has the strongest influence on -

recently formed, direction of cell expansion

Three lines of evidence that cortical microtubules guide the deposition of cellulose microfibrils

1. microtubules and microfibrils are often coaligned during cell wall synthesis

2. microtubules mark sites of CesA localization and microfibril formation

3. disruption of microtubules disrupt microfibril orientation

all in the inner most cell wall

expansin enzymes play a key role in - (two things)

cell expansion and stress relaxation

stress relaxation of cell wall drives - and -

water uptake, cell elongation

model of expansin activity

1. expansins will slide along -

2. expansins recognize attached - under -

3. expansin removes part of the -

4. results in partial -, which allows cellulose microfibrils to slip -

cellulose microfibrils, glycans, tension stress, attachment, stress relaxation, further apart