Plant Structure and Systems Flashcards
What is the shoot system?
adapted to the need for acquiring resources from above the ground, in the atmosphere
made up from the
leaves: broad surface to maximize photosynthesis and gas exchange
stems: elevate leaves to assist with photosynthesis and reproduction
depends on water/minerals acquired from the root system
What is the root system?
adapted to the need to acquire nutrients from below the ground, in the soil
made up from the
tap root: central root that anchors the plant, providing support
lateral roots: branched roots that absorb both water/nutrients
depends on the sugars made in the shoot system
What are the three primary organs in the shoot and root systems?
Roots
Stems
Leaves (including flowers)
What are the three tissue types?
Dermal
Ground
Vascular
What is the dermal tissue?
outer protectie layer
epidermis: in non-woody plants
periderm: in wooded plants
What is the vascular tissue?
conduct fluid movement
xylem: water/dissolved minerals move up
phloem: sugars move down (or to the fruits)
What is the ground tissue?
all other functions
photosynthesis
storage
physical support
What does the xylem do?
conveys water and dissolved mineral upward from roots into the shoots, for photosynthesis
made of dead cells
fortified with lignin
What does the phloem do?
moves photosynthetic sugar from stem and leaves to roots and other growth sites
made of living cells
What are tracheids?
exist in all vascular plants while vessel elements are in most angiosperms
part of the xylem
What are pits?
part of tracheids (of xylem) that allow bulk movement of fluid through cells vertically and laterally
What are perforation plates?
part of tracheids (of xylem) in vessel elements to assist fluid movement
What are sieve-tube elements?
special cells that have lost nucleus, ribosomes, vacuoles, and cytoskeleton to assist in nutrient movement
What are companion cells?
neighbor cell with nucleus and ribosomes to make the proteins for sieve-tube element.
What did the vascular system allow for?
the development of true roots, stems, and leaves
movement of nutrients over greater distances
structural support for heavier organisms
What are the primary roles of the root system?
anchoring (support)
absorbing water/minerals
storing organic nutrients
What do primary roots develop into?
taproot system: one main vertical root that gives rise to lateral roots, which branch outward for absorption
fibrous root system: monocots and seedless vascular plants lose the primary root and develop network of lateral roots from the stem
What are root hairs?
they conduct most of the absorption
finger like extensions that grow from elongating roots
increase surface area of branching roots
most absorption occurs through cells of the root hairs
most mycorrhizal interactions occur here
What modifications have roots undergone?
prop roots: support tall, top-heavy plants
storage roots: taproot has evolved to store tons of sugar
air roots: some is above the ground, to acquire oxygen
buttress roots: shallow root systems
How does vascular bundles differ in monocots and eudicots?
monocots: vascular bundles are more dispersed
eudicots: central star-like stele of vascular tissue
What is the primary role of the stem?
to bear the buds and leaves of the root system, in order to position them such that they can maximize photosynthesis
raise reproductive structures to help pollination/seed dispersal
What do stems consist of?
alternating systems of nodes
What is a node?
points where the leaves are attached, by growing from buds
What is the apical bud?
terminal bud: located at the shoot tip, and elongates the main, central stem
What is the axillary bud?
buds that can form lateral stalks, which attach to leaves, thorns, flowers or even entirely new branches
What modifications have stems undergone?
rhizomes: horizontal stem just below the surface which gives rise to shoots
bulbs: underground shoots that give rise to enlarged storage leaves
stolons: horizontal shoots along soil surface, allows asexual reproduction
tubers: enlarged ends of rhizomes or stolon stems used for food storage
What is the primary role of leaves?
to conduct the process of photosynthesis
What are the secondary roles of leaves?
to conduct: gas exchange heat dissipation herbivore defense cone, flower, fruit development
How does the vascular tissue form assist photosynthesis?
vascular tissue of the leaf connects with the vascular tissue of the stem to move materials both need and produced by photosynthesis
called veins in the leaves, which also act as structural support
How does the dermal tissue form assist photosynthesis?
the epidermis reduces water loss by forming tight layer that makes the cuticle
the waxy cuticle also protects against pathogens from entering
ground tissue in a leaf is called mesophyll
What is the purpose of stomata?
allow CO2 exchange between the air and the photosynthetic cells
pores are flanked by guard cells which regulate opening and closing
How does the ground tissue form assist photosynthesis?
called the mesophyll has two layers:
palisade mesophyll: photosynthetic cells that are tightly packed
spongy mesophyll: photosynthetic cells that are arranged loosely, such that gas exchange can occur within the leaf
What the three morphologies of leaves?
simple
compound
doubly compound
What is a simple leaf?
single, broad, undivided blade (can be lobed)
What is a compound leaf?
many “leaflets” come from petiole; no axillary bud at base
What is a doubly compound leaf?
the “leaflets” are divided again into smaller leaflets
What are the three heavily modified forms of leaves?
tendrils: provide support
spines and thorns: protection
storage leaves: house both water and food
What are parenchyma cells?
when mature:
they have thin flexible primary walls
generally lack secondary walls
have a large central vacuole
perform the most metabolic functions
retain the ability to divide and differentiate
Examples: phloem cells, photosynthetic cells, some storage tissues
What are collenchyma cells?
grouped in strands and help support young parts of the plant shoot
they have thicker and uneven cell walls
these cells provide flexible support without restraining growth
often serve as mechanical support (especially for young or growing parts of the plant)
What are sclerenchyma cells?
highly specialized for mechanical rigidity
thick secondary walls, often strengthened with lignin for rigidity
usually elongated when mature; resistant to bending, cannot grow
often dead at maturity (no active biochem need for function)
examples: xylem cells, fibers, and sclerids
