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
True or False:
Metaphloem development starts before organ stops growth in length
False: after
Metaphloem in woody dicots is crushed by what?
Secondary phloem
Variations in Stem Architecture:
- common in roots
- cylindrical core of xylem surrounded by phloem
Prostele: Haplostele
Variations in stem architecture:
- common in stems of whisk ferns, and roots of seed plants
- lobed core of xylem surrounded by phloem
Prostele: Actinostele
Variations in stem architecture:
- common in modern club mosses
- interconnected plate-like regions of xylem surrounded by and immersed in phloem tissue
Protostele: Plectostele
Variations in stem architecture:
- common in ferns
- has two types
Siphonosteles: Solenostele
Variations in stem architecture:
Type of Solenostele:
Phloem to the exterior of xylem
Ectophloic
Variations in stem architecture:
Type of Solenostele:
Phloem to both sides of xylem
Amphiphloic
Variations in stem architecture:
- common in stems or rhizomes of ferns
- multiple leaf gaps result in a net-like arrangement
Siphonostele: Dictyostele
Variations in stem architecture:
- stem of seed plants; eudicots
- discrete vascular bundles are arranged in a field of pith
Siphonostele: Eustele
Variations in stem architecture:
- monocots
- Subtype of eustele in which vascular bundles are apparently scattered throughout the pith
Siphonostele: Atactostele
Secondary growth patterns in eudicots:
name the three
- connection of vascular bundles through interfascicular cambium
- single ring of vascular cambium that produces concentric rings of vascular tissues
- Separation of individual bundles due to interfascicular cambium producing parenchyma that causes pith rays.
Secondary growth in monocot stems:
where do they gain significant support from?
sclerenchyma tissues and fibrous strands:
- arenchyma- filled stem
- large bundles of fibers
- heavy sclerified vascular bundles
Secondary growth in Monocot Stem:
what are the 3 mechanisms to increase diameter and strength
- primary thickening meristems
- secondary thickening meristems
- intercalary meristems
Secondary growth present in?
ALL gymnosperms
MOST basal angiosperms (herb)
MANY Eudicots (herb)
Secondary growth absent in
Ferns and monocots
Why must gymnosperms and woodydicots increase amount of vasculature?
accommodate increase in stem and root diameter and serve a large shoot and root system to increase support and transport of plant
Vascular cambium:
mitosis produces what
xylem initials: to inner side
phloem initials: to outer side
Why do initials undergo multiple mitosis rounds?
to contribute to girth and maturity of stem and root
True or False:
TRUE vascular cambium is multiple layered
False: one cell layer but has cambial zones
How do initials divide?
mostly periclinally and are bifacial (produce both inner and outer sides)
secondary phloem deriavtives to the outside
secondary xylem derivatives to the inside
What happens when Vascular cambium process continues?
older phloem to the exterior gets crushed and xylem cells to interior differentiate into woody tissue (lignification)
What CAN NOT further develop primary vasculature and why?
monocots and herbaceous eudicot; Vascular bundle is closed
What CAN further develop primary vasculature and why?
gymnosperms and woody eudicot; Vascular bundle is open and contains fascicular and interfascicular cambium
Vascular Cambium cell types:
- conducts materials up and down plant axis
- consist of xylem, phloem, and their derivatives
Axial system
Vascular cambium cell types:
- move materials in short distance from axial system outward to living portion of bark
- with phloem and xylem rays from (parenchyma and some sclerenchyma)
Radial system
Elongated and tapered parenchyma cells that produce axial system elements of secondary tissues
Fusiform initials
True or False:
One fusiform initial will always remain as cambium
True
True or False:
Phloem is produced more than xylem
False: xylem is produced more than phloem
Type of cell division:
Longitudinal cell division with a wall PERPENDICULAR to cambium surface
Anticlinal Division
Type of cell division:
Longitudinal cell division with a wall PARALLEL to circumference of cambium
Periclinal Division
Shorter cells, cuboidal, elongated along radial axis and generate cells of radial system and undergo periclinal division
Ray Initials
Initial cell arrangement:
tapered end walls that are aligned in the same plane, uncommon and has short fusiform initials and has multiseriate rays
Storied cambium
Initial cell arrangement:
irregular; ends of walls are not alligned, most common with long fusiform initials, and has uniseriate rays
Non-storied cambium
What is wood
multiyear accumulation of xylem growth, is widely used plant product in the world, and functions as support and conduit of water
Wood composition:
What are the steps of wood manufacturing
- cell division
- axial and radial enlargement
- cell wall thickening
- programmed cell death
What happens to xylem and phloem in wood?
xylem becomes one tree ring and phloem becomes crushed and incorporates into periderm
Sections of wood:
perpendicular to long axis of stem and reveals annual growth rings
Cross-section
Sections of wood:
parallel to longitudinal axis and runs through center of stem; expose side view of rays from center to exterior
Radial section
Sections of wood:
also parallel but off-center and allow visualization of end of rays
Tangential section
Wood density:
gymonsperms - lack fibers
softwood
Wood density:
angiosperm eudicot - with vessel elements and fibers
hardwood
Wood pigmentation:
outermost region, lighter color, high moisture level, stores some energy reserves
Sapwood
Wood pigmentation:
innermost region, darker color, less water and mineral reserves, not active in translocation
Heartwood
Formed when plant is under stress, it is non-conducting and prone to fungal invasion. plug for water retention
tyloses
True or False:
vascular is inactive during extreme seasonal climate
True
Always has one layer of cork cambium, cuboidal and forms phelloderm in the inner and phellem in the outer
Cork cambium/pellogen
chemically inter and water proof, prevents animals from eating it due to cell death, and temporary protection of inner organs of stem
Periderm
Type of bark:
all tissues outside the innermost cork cambium
outer bark
Type of bark:
all secondary phloem between vascular cambium and innermost cork cambium
inner bark
Stem modification:
Supporting itself by the main or lateral stems coiling around a structure or another plant
Support; Twiners
Stem modification:
Slender coiling structure derived from branch and used in climbing
Support; Tendril
Stem modification:
Slender process with curved or bent part at the tip for latching
Support; Hooks
Stem modification:
Grows upwards by attaching itself to other structures for support; adventitious roots that arise from stem
Support; Root climbers
Stem modification:
Underground stem, distinguished from root by its nodes, buds or scale-like leaves
Storage; Rhizomes
Stem modification:
thickened branch of underground stem, serving as storage organ, distinguished by bearing leaves, leave scars, and auxiliary buds
Storage; tubers
Stem modification:
underground storage organ where bud is enlcosed by fleshy scale leaves and/or leaf bases
Storage; blubs
Stem modification;
Short underground swollen storage stem
Storage; corm
Stem modification:
Pointed woody structure derived from reduced branch
Protection; thorn
Stem modification:
Sharp outgrowth from the epidermis, detachable without tearing organ
Protection; prickle
Stem modification:
vegetative shoot spreading along surface of the ground
Reproduction; runner/stolon
Stem modification:
Rooting at nodes where it may give rise to new plantlets
Reproduction; underground/stem budding
Stem modification:
Portion of stem or branch flattened and expanded to serve the functions of a leaf
Photosynthesis; Phyllocladde/Cladode
Stem modification:
laterally flattened photosynthetic blade, undeveloped or underdeveloped rachis and pinnae that serve purpose of leaf
Photosynthesis; Phyllodde
Stem modification:
Stems may be chlorophyllous and add to photosynthetic capacity of plant
Photosynthesis: Photosynthetic stem
