Plant Stem Flashcards
Function of stem:
- maximize photosynthesis
- proper orientation of shoot system
- elevate reproductive organs
Orient shoot
Function of stem:
Needed for long-distance transport of water, minerals, photosynthesis, and hormones
Conduits of vascular tissues
Where does the stem develop from?
epicotyl and sometimes hypocotyl
Stem classification
- Organization and structures; presences or absence of secondary growth
- evolutionary origin; plant groups
Plant groups
monocots
herbaceous eudicot
woody dicot
Presence or Absence of secondary growth:
Without persistent woody stem; herb with annual stems from a perennial roots
Herbaceous
Presence or Absence of secondary growth:
with woody tissues; having great girth; common to large shrubs and trees
Woody
Presence or Absence of secondary growth:
subshrub; plant with annual soots from a woody subterranean base
Suffrutex
What do you call a plant that does not possess a stem?
Acaule
ex. duckweed family
External Features:
where leaves are attached
Nodes
External Features:
regions between nodes; developed by intercalary growth
Internodes
Internode:
no organized meristem, mitotic activity occurs between nodes
Intercalary growth
External Features:
corky eruptions in bark that allow gas exchange
Lenticels
External Features:
Remnants of other structures of other structures when they are lost, damaged or abscised
Scars
External Features:
under developed or resting meristems; immature shoots with or without bud scales ~ leaf coverings
Buds
Classification of buds based on development:
give rise to branch of leaves
Vegetative bud
Classification of buds based on development:
give rise to flowers or group of flowers
Floral bud
Classification of buds based on position:
apical; at extreme tip
Terminal bud
Classification of buds based on position:
auxilliary; located at leaf axils
Lateral bud
Classification of buds based on position:
Additional to lateral buds
Accessory bud
Classification of buds based on position:
located other than nodes (internodes, leaves, roots)
Adventitious bud
Internal Features - Stem Histology:
consists of epidermis, cortex, ring of vascular tissues, and pith
Eudicot
Internal Features - Stem Histology:
Vascular bundles are intertwined with ground tissues ~ medullary bundles
Monocot
Dermal Tissues:
covers stem interior; consists of single layered epidermal cells covered with___
Epidermis
Waxy cuticle
Ground Tissues:
Layer between epidermis and vascular tissues
Cortex
Ground Tissues:
- Region of cortex consisting of one or more layers of cells lying under epidermis
- made up of pure, weak parenchyma cells that are laid early which can destroy pith during primary growth
- Functions:
___
___
Hypodermis
Functions:
Storage
Support
Ground Tissues:
- Inner cortical region containing casparian strips
- provides barrier between two regions limiting layers between stele and cortex
Endodermis
Vascular Tissues:
FIRST development of xylem, flexible, short-lived
Protoxylem
Vascular Tissues:
Development of xylem right before maturity, less flexible, long life span but still becomes useful after death
Metaxylem
Vascular Tissues:
FIRST development of phloem, flexible, short-lived
Protophloem
Vascular Tissues:
Development of phloem right before maturity, Long life span and continuously functional
Metaphloem
Phloem surrounding the xylem
Amphicribral
Xylem surrounding the phloem
Amphivasal
Phloem is to the outside or abaxial to the xylem
Collateral bundle
Primary phloem may be found on both the inner and outer sides of the xylem
Bicollateral bundle
Patterns of xylem development in stem:
Protoxylem in the middle, surrounded by Metaxylem
Centrarch
Patterns of xylem development in stem:
Same with centrarch but with multiple vascular strands
Mesarch
Patterns of xylem development in stem:
- Metaxylem is exterior/abaxial of protoxylem
- Common in angiosperm stem
Endarch
Patterns of xylem development in stem:
- Metaxylem is interior/abaxial of protoxylem
- common in angiosperm roots
Exarch
What are monocots lacking in and why?
Secondary phloem; no secondary growth
Primary phloem is____, no _____ in gymnosperms, monocots, or eudicots
axial; radial primary vasculature
True or False:
Metaphloem sieve tube elements are large than those found in protophloem
True