BFG Ch 4: inside roots and leaves Flashcards
Arrangement of roots
outside is epidermis
cortex occupies a large portion of the organs volume (more than in the stem)
Loose packing of cortex cells allows for oxygen and water movement; starch grains found here
Vascular tissue in the center (primary xylem in X shape and primary phloem)-
Where is the vascular cambium in roots?
single row of cells between the primary xylem and primary phloem
What surrounds the vascular tissues of roots?
single layer of cells called the endodermis
water and mierals are directed as they make their way to the phloem through the endodermis
What are pericycle cells
Immediately inside the endodermis (between endo and the vascular tissue)
place from which branch roots arise
this location offers protection to the site of branch formation in case a root is damaged.
Transition from root to stem
the central vascular tissues of the root divide up into the peripheral bundles seen in herbaceous stems.
Pith is inserted between bundles aboveground
Describe secondary growth in roots
thicken the same way as trunks
vascular cambium lays down wood (secondary xylem) and inner bark (secondary phloem)
cork cambium produces cork onthe outside
presence of cork greatly reduces water uptake from soil in older roots
Where does most water absorption occur?
root hair zone
Describe the cellular organization of a leaf (sandwich)
epidermis palisade cells of mesophyll spongy cells of mesophyll (veins going through mesophyll) lower epidermis cuticle
mesophyll in leaf sandwich (2 parts)
elongated palisade cells in the upper epidermis; catch the first light entering the leaf
spongy cells; loosely packed to allow gas excahnge with some chloroplasts to capture some light that passes through the palisade layer
How far away are mesophyll cells from veins?
usually only a few cells at most.
Leaf veins
contian a few xylem and phloem
supply mesophyll with water and remove newly made foods such as sugar
Cuticle layer of leaf
on the outer surface of both upper and lower epidermis
provides a barrier against dessucation
Other than a cuticle, how can a leaf protect itself against water loss?
silver-gray epidermal hairs help reduce evaporation from tiny pores in leaf surface
act as a deterrent to insect browsers
reflect a portion of sunlight (same as cuticle) to safeguard against sun in the desert
stomata
located on lower epidermis, gas exchange and water vapor escape
don’t want to get plugged with dust or fungal spores
leaves standing in an upright position tend to have equal numbers of stomata on both sides.
Stomata at night
most of the time they close to conserve water loss because they don’t need CO2 anyway
