IB Bio Leaf & Transport System

protective covering of one or more cell layers; living tissue; some cells modified in guard cells

made of cutin (waxy substance on epidermis); non-living material; reduces transpiration (water loss)

epidermis & cuticle

specialized epidermal cells that control open & close of stomata; make up stomata

consist of parenchyma cells (ground tissue) w/ many chloroplasts; usually in one layer but can be on both sides of leaf in arid climates

pores in epidermal layer of leaf; found only on bottom of leaves in shade

in = co2; out = o2, water vapor

no b/c waxy layer would block diffusion

close stomata

on top of leaves

consist of parenchyma cells loosely arranged below palisade mesophyll

has many empty chambers for co2 storage

palisade & spongy mesophyll

consist of xylem & phloem tissue (veins in leaf);

bundle sheath cells (specialized mesophyll cells) --> no exposure of vascular bundles to intercellular spaces

prevent air bubbles from entering vascular tissue b/c air bubbles stop flow of water from roots --> leaves & sugar water from leaves --> roots

cuticle, upper epidermis, cuticle, palisade mesophyll and spongy mesophyll w/ vascular bundles partially in between them, cuticle, second lower epidermis, & another cuticle

water enters cell walls & moves from one cell to another w/o ever entering cell's other living tissues; blocked by suberin contained in caspian strip

water moves from cytoplasm of one cell to next cell's cytoplasm thru plasmodesmata; when water reaches endodermis --> can only go into vascular cylinder thru this pathway (endoderm cells let water in but only some ions)

tunnel of cytoplasm connecting plant cells

diffusion of water; how water moves from soil --> inside root hairs

maintained by root by keeping certain minerals & removing water

concentration gradient forces water even higher up root

major cause of water theory; due to unequal pressure @ leaves & roots --> water pushed from roots to leaves; movement cont. until pressure is even throughout plant

na+ ions enter (active), water follows (passive)

prevents (-) pressure w/ leaves & xylem tissue

produces single polymer-like water column from roots --> leaves

1. bulk flow of water thru xylem cells occurs as water molecules evaporate from leaf surface & pulls up water column behind it

2. H bond btwn H & O of H2O --> water acts as single polymer moving together

high pressure b/c water keeps entering by osmosis but doesn't reach equilibrium b/c ions enter by active transport

low pressure b/c water evaporates thru stomata --> less water molecules

minimize water loss, intake lots of CO2

have uneven cell walls

• thick walls on inside b/c doesn't need to stretch as much

• thin walls on outside b/c needs to stretch more

• increase turgor pressure

• cell walls stretch & become kidney-shaped

• stomata open

• decrease turgor pressure

• cell walls no longer stretch

• stomata close

• prevents water from being released

• decreased CO2 concentration

• day of day = night

• increased amounts of K+ ion enter cell

• increased temp

• time of day = daytime

K+ ion enters thru active transport in guard cells --> increases concentration of solution inside of cells --> concentration gradient --> H2O diffuses from surrounding cells into guard cells --> increases turgor pressure inside --> cell walls stretch unevenly --> stomata opens

movement of carbs thru phloem from source to sink

pressure flow hypothesis

1. glucose enters sieve-tube members by active transport from leaf cells --> high pressure at top of sieve tube --> creates concentration gradient

2. water enters sieve-tube by osmosis (passive)

3. turgor pressure builds up --> water & glucose moves by bulk flow away from source to equalize pressure

4. water leaves sieve-tube by osmosis & glucose leaves by active transport into roots --> tube = area of low pressure again

5. carbs are used by sinks --> solution = hypotonic

eventually pop but water can be transported back up to leaves thru xylem

where sugar is delivered (roots)

where substances are produced or enter plant (leaves)