Quiz 3: Stems Flashcards
what are 4 characteristics of stems
- generally above ground
- must have buds (apical and or axillary )
- support for leaves, flowers ect
- conduits of vascular system
differences between vascular arrangement between monocot and dicot
- monocot: distributed through stem
- dicot: ring structure
what is a node? what are 3 different types of leaf distributions
- segment of the stem at which leaves and axillary buds are attached
1. alternate: 1 leaf/ node
2. opposite: 2 leaves / node
3. whorled: 3 or more leaves/ node
what is internode?
segment of stem between 2 nodes
what is petiole
‘stem’ - attaches the leaf blade to the actual stem
apical vs axillary
- apical at end of stem
- axillary where leaf meets the node of the stem
what are 6 factors that influence internode length
- fertility of soil
- season (time of year) - daylength
- vigour
- stress
- competition
- light levels
what is etiolation
- tissue that doesn’t have chlorophyll ( appears white)
apical bud
-bud at tip of stem
apical meristem
-region of actively dividing cells at tip of a growing root or stem
axil
angle between the upper surface of a leaf and the stem to which its attached
axillary bud
bud located at axil at the base of a leaf
axillary bud primordium
immature axillary bud
describe apical dominance
apical bud creates hormones that control growth of plant further down
- if removed = promoted growth further down/ branching
- further down a tree is the less influence the apical bud has ( pyramidal shape)
what is coppicing
- cut plant/ shrub close to ground in fall to get new, more shoots next season
what are 5 external features of stem that can help in plant ID?
- lenticels: small gas exchange opening in cork of a woody stem
- leaf scar: scar left on stem after leaf has fallen
- bud scales: terminal bud scales mark each years growth
- bundle scar: where vascular bundle enter leaf
- pith: spongy, central cylinder of tissue found inside stem
Secondary growth:
a) occurs in which plants
b) describe where occurs in trees and shrubs
a) gymnosperms and dicots, not usually monocots- palm tree exception
b) trees- one or few trunks to support tall leafy growth
shrubs- many woody stems that branch closer to the ground
advantages and disadvantages of woody growth
pros
1. exploitation of niche- reaching for sunlight
2. protection of tissue- vascular system protected from predators
3. support- branching over wide areas
4. longevity- up to 1000s of years
cons
5. costly- energy and time
6. flexibility- brittle susc. to wind damage
what does xylem mean in greek
wood
purpose of xylem, describe structure
a) - transport of water upwards from roots
- pipeline of cells arranged from end to end
b) -cells die at maturity leaving a hollow tunnel
- cells walls are thick with cellulose and lignin - support and strength
what are 2 types of xylem
- tracheids
2. vessel elements
describe tracheids xylem
- long narrow cells with end walls and pits for water to move between
- provides strength
- found in primitive plants ( gymnosperms)
- cannot move water a lot of water quickly
describe vessel elements xylem
- short, wide cells without end walls and are stacked on top of each other
- move more water than tracheids
what plants utilize which xylem type
- angiosperms have tracheids and vessel elements
- gymnosperms only tracheid
what does phloem mean in greek
tree bark
what is main purpose of phloem
- transport dissolved sugars ( sap) fro source (where made) to sink ( where stored) –> bi- directional
what are 2 types of cells found in phloem
- seive tube members
2. companion cells
describe seive tube members
- stacked into tube forms ( seive tubes) with porous seive plates between the cells for movement of sugars
describe companion cells
- along each seive tube member and help
in loading sugar into the seive tube
-direct actions of seive tube member cells
-living at functional maturity
describe vascular bundles in monocots
- scattered throughout the ground tissue
- bundles located close to rind of stem are smaller and closer together
- contain no cambium –> no secondary thickening occurs
what are 3 components of monocot vascular bundles
- sclerenchyma sheath
- xylem
- phloem
- sclerenchyma sheath - mono vasc bundles
- thick walled, fibres surround vascular bundle
- protects vascular bundle and gives support
- xylem - mono vasc bundles
-large vessels found in an irregular intracelleular space ( lysigenous cavity)
what in lysigenous cavity
- where xylem is located
- surrounded by thin walled parenchyma cells –> lignified so strengthen the stem
describe vascular bundles of dicots
- situated inside of pericycle of plant in unique
- mature vasc bundle contains xylem, phloem and cambium
where is cambium located, where is it found,
- between xylem and phloem
- responsible for secondary thickening
when does secondary growth occur
- occurs if vasc. cambium continues to produce cells
- dif bundles linkup to form a (almost) circle
- ring makes up new cells, xylem in inside, phloem on outside
- where cambia don’t quite meet, pith/ cortex form beg. of medullary rays
- after a few rounds , vasc bundles forms neat ring
where is oldest xylem and phloem found in relation to tree?
- xylem at centre of trunk
- phloem just under bark
what is dendrochronology
study of tree internal rings to determine age
describe spring xylem
- slower growth, less water
describe summer xylem
-rapid growth, large amounts of water moving through
describe 5 types of modified stems
- bulb
- corm
- tuber
- rhizome
- stolon
describe bulb
a) what is it
b) what is it comprised of
c) tunicated vs non tunicated
a) - short flattened stem bearing fleshy, food storage leaves
b) compressed stemor basal plate and modified scales
c) outermost scale dried out and papery, serving as protection for fleshy scales beneath ex tulip bulbs , bulbs that lack papery coverign non tunicated ex lilly
what are function of modified scales
- on bulbs, serves as primary storage tissue
what is corm
- solid modified stem consisting of a swollen base of a stem axis enclosed in dry, scale like leaves
-fibrous and contractile roots
-mod. stem with basal plate, but primary storage tissue is the stem tissue itself rather than leaf tissue
= solid bulbs
ex gladiolus
describe tuber
thickened underground stem, stem tissue sreves as its primary storage tissue
- unlike corm, no basal plate
- meristems called ‘eyes’ on potato
- caladium is most common type
describe rhizome
- stem primary storage tissue
-grows horiz. through soil = underground horiz stems
ex lillies, iris, turf
describe stolon
- horiz stem growing above ground that may form roots and vertical shoots at its tips / nodes
- also in turf grass
