STEM n LEAVES Flashcards
Generally expanded and flattened green structure growing out at the nodes of the stem
LEAVES
Main organ of the for photosynthesis
LEAVES
Parts of dicot leaf
- Petiole or leaf stalk
- Lamina or leaf blade
Cylindrical or flattened structure which supports and holds the leaf upright
PETIOLE OR LEAF STALK
Conducts materials to and from the leaves
PETIOLE OR LEAF STALK
Small, leaf-like outgrowths at the base of petiole is called
STIPULES
Leaves without petioles is called
SESSILE LEAVES
Thin, flattened, usually green expanded part of the leaf
LAMINA OR LEAF BLADE
Shapes of a dicot leaf
- Linear - long and slender
- Cordate - heart-shaped
- Ovate - egg-shaped
- Deltoid - triangular
- Reinform - kidney-shaped
- Cuneate - wedge-like
- Flabellate - fan-like
- Orbicular - disk-like
Apex of a dicot leaf
- Pointed
- Emarginate - notched
- Rounded - arch-like
- Caudate - tail-like
- Flattened
Margin of a dicot leaf
- Entire
- Dentate - tooted and serrated
- Lobed
- Scalloped
- Cleft
Base of a dicot leaf
- Sagitate - arrow-shaped
- Auriculate - ear lobed-shaped
- Peltate - petiole is attached at undersurface
- Rounded - arch-like
- Truncate - flattened
- Cordate - heart-shaped
Parts of monocot leaf
- Leaf sheath
- Leaf blade
- Ligules
- Auricles
The support of the leaf which may completely envelope the stem of a small flap of delicate
tissue extending upward called the ligule.
LEAF SHEATH
Thin expanded portion above the sheath
LEAF BLADE
Are membranous or hairy tissues located at the junction of the leaf blade and leaf sheath
LIGULES
Are slender extensions of the collar and are located at the junction of the leaf blade and leaf sheath.
AURICLES
Variation in leaf structure
- Leaf blade configuration
- Venation
- Phyllotaxy
The blade consists of only one
piece
SIMPLE LEAF
Another type of leaf blade configuration
Compound leaf
The blade is divided into two segments called
LEAFLETS OR PINNAE
The stalk of each leaflet is called
PETIOLULE
Two types of compound leaf
- Pinnately compound leaf
- Palmately compound leaf
The leaflets are attached to the extension of the petiole called rachis
PINNATELY COMPOUND LEAF
The leaflets are attached to the extension of the petiole called ___
RACHIS
The leaflets radiate from the upper end or tip of the leafstalk
PALMATELY COMPOUND LEAF
It is the arrangement of veins
Venation
Two types of venation
- Netted or reticulate venation
- Parallel venation
Veins branch profusely and form a network over the blade; found in dicots
Netted or reticulate venation
Veins do not form a network;
found in monocots
Parallel venation
Veins and their branches spread out in all directions from the midrib, the continuation of petiole
Pinnately netted
Several midribs arise from the tip of the petiole and spread fan-like through the blade
Palmately netted
Several midribs arise from the tip of the petiole like the ribs or spokes of an umbrella and then breaks up into smaller veins; found in leaves where petiole is more or less at the center of
the blade
Radiately netted
Three types of netted or reticulate venation
- Pinnately netted
- Palmately netted
- Radiately netted
Two types of parallel venation
- Parallel venation with veins parallel to the midrib
- Parallel venation with veins at acute or right angles to the midrib
The system of leaf arrangement on the stem
Phyllotaxy
Two types of phyllotaxy
- Whorled (verticillate)
- Fasciculate
A leaf arrangement where three or more leaves located at around the node
Whorled (verticillate)
A leaf arrangement where two or more leaves are located only on one side of the node
Fasciculate
Types of position in leaf orientation
- Dorsiventral or bifacial leaves
- Isobilateral or equifacial leaves
A position of leaf where leaves are horizontally oriented and the upper or ad-axial surface receiving direct sunlight
Dorsiventral or bifacial leaves
A position of leaves where leaves are vertically oriented and the two surfaces are receiving direct sunlight
Isobilateral or equifacial
Functions of the leaves
- Photosynthesis
- Transpiration
Types of modified leaves
- Spine
- Motile leaves
- Succulent leaves
- Tendrils
- Supporting leaf bases “pseudotrunk”
- Insect traps
- Adventitious buds
- Attraction of pollinators
- Aeration
- Photosynthesis
No blade and needle-shaped, no mesophyll, no vascular tissue, has closely packed fibers in mesophyll
Spines
Display “thigmonasty” sensitivity to touch, for protection
Motile leaves
A tropic response to touch
Thigmotropic response
Thick and fleshy, reduced surface-volume-ratio; with water storage parenchyma; Crassulaceae, kataka taka
Succulent leaves
Sensing contact with other objects, no lamina, support; side facing the object stop growing, otherside elongate— coil
Tendrils
For support
Supporting leaf bases “pseudotrunk”
Digest insects and obtain nitrogen for their amino acid
Insect traps
Produce plantlets
Adventitious buds
Colored leaves for attraction
Attraction of pollinators
Floats – aerenchymatous leaf base for buoyancy,
support
Water hyacinth – aerenchymatous enlarged leaf base
Aeration
Two types of aeration
- Floats – aerenchymatous leaf base for buoyancy,
support - Water hyacinth – aerenchymatous enlarged leaf base
Expanded leaf-like petiole or stipule – added
photosynthesis
Photosynthesis
Economic importance of leaves
- Food source
- Fiber source
- Tea leaves
- Tobacco leaves
- Some drugs obtained from leaves
- Used as flavoring
Types of stem
- Shoot
- Twig
- Branch
- Trunk
Are plant organs which are continuations of the roots usually located above the surface of the soil
STEM
A young stem (1 year old or less) with leaves
SHOOT
A young stem (1 year old or
less) that is in the dormant winter stage (has no
leaves).
TWIG
A stem that is more than
1 year old, typically with
lateral stems radiating from it
BRANCH
A woody plant’s main stem.
TRUNK
The stem with its leaves is called a _____ and all the stems and
leaves of a plant constitutes its
_____.
Shoot, shoot system
Stems originate from the _____ and partly from the _____ of the embryo.
Epicotyl, hypocotyl
Classifications of stems (DIAGRAM)
DIAGRAM
Two types of stem classification based on toughness
- Woody stem
- Herbaceous stem
What do you call the stems that are woody only at the base
Suffrutescent stems
External structures
- Nodes
- Internodes
- Leaf scar
- Bundle scars
- Lenticels
- Buds
Swollen areas where leaves, branches and buds arise
Nodes
Portion between two nodes
Internodes
Mark left on the stem by a
fallen leaf
Leaf scar
Cut ends of the vascular bundles within each leaf scar
Bundle scars
Raised pores seen on dicot stems
Lenticels
Undeveloped structures which may grow into leaves, shoots, or
flowers
Buds
Types of buds based on location and position of the stem
- Terminal or apical bud - at the end of the stem
- Lateral or axillary bud - at the upper angle
- Accessory or supernumery buds - beside and above the axillary buds
- Adventitious buds - on other parts of the plants such as leaves, roots or internodes
Two classification of stems based on location
- Aerial stems (Epiterranean stems)
- Underground stems
What do you call the stem where the leaf stalk formed the lateral or axillary bud
Leaf axil
Two types of aerial stems
- Runners (stolon)
- Tendrils (scramblers)
Fleshy or semiwoody, elongated, horizontal stems that often lie along the soil surface
Runners (stolon)
These are thread like structure
which help the plants in
climbing
Tendrils (scramblers)
Types of underground stems
- Rhizomes
- Tubers
- Bulbs
- Corm
Underground, horizontal stem which may be swollen due
to the presence of stored food
Rhizomes
Short, swollen, terminal portions of an underground stems with the stored food
TUBERS
Very small piece of the stem
tissue surrounded by numerous
fleshy leaves
Bulbs
Globose, underground stem
with thin, papery leaves on its surface
Corm
Modified or specialized functions of stems:
- Unusual method of support
- Photosynthesis
- Uncutinized epidermis
- Reproduction
- Storage
- Protection
Stems that are found in both monocot and dicot plants
Herbaceous stems
Stems that are found only in dicot plants
Woody stems
