stem Flashcards
continuations of the
roots usually located above the surface of the
soil
STEMS
Originate from the epicotyl and partly from the
hypocotyl of the embryo
STEMS
New plant growth
SHOOT
Above ground parts of the plant
SHOOT SYSTEM
CLASSIFICATION OF STEMS BASED ON
TOUGHNESS
HERBACEOUS STEMS
WOODY STEMS
SUFFRUTESCENT STEMS
*Non-woody, soft and green in color
* More common in Monocot and but also found
in some dicot plants
* Example is bell pepper (Capsicum annuum)
HERBACEOUS STEMS
- Hard and rigid because of the secondary
growth or cork formation - Dicot plants
WOODY STEMS
Woody only at the base
* Example is eggplant (Solanum melongena)
SUFFRUTESCENT STEMS
— Very little or absent and thus is generally soft
— Short-lived
— Very little growth in diameter
— Smooth, thin epidermis
— Green
— stomata is Present
HERBACEOUS STEMS
— woody tissue is Present, thus are hard and thick
— Long-lived
— Increases in diameter (mainly due to production of wood & cork)
— Rough cork
— Green when young, brown when old
— stomata is Absent, but with
lenticels
WOODY STEMS
pores of outer plant tissue that provide direct exchange of gases between internal plant
tissues and atmosphere
LENTICELS
above the surface of soil
AERIAL STEMS
- are horizontally oriented stems that grow along
the soil surfaces - example is strawberry (Fragaria ananassa)
RUNNERS OR STOLONS
- coil around objects and help support the plant
- Ampalaya (Momordica charantia)
- Grapes (Vitis vinifera)
- Melon (Cucumis melo)
- Squash (Cucurbita maxima)
TENDRILS OR SCRAMBLERS
CLASSIFICATION BASED ON LOCATION
AERIAL STEMS
UNDERGROUND OR SUBTERRANEAN
STEMS
- Beneath the surface of the soil
UNDERGROUND OR SUBTERRANEAN
STEMS
- underground, horizontal stem which maybe
swollen due to presence of stored food - ginger (Zingiber officinale)
- asparagus (Asparagus officinalis)
- turmeric (Curcuma longa)
- bamboo (Bambusa bambos)
RHIZOMES
- short, swollen, terminal portions of an
underground stems with stored food - specialized for storage
- potato (Solanum tuberosum)
TUBERS
- very small piece of stem tissue bearing
numerous fleshy leaves - onion and garlic
o tunic or tunica – papery layer of bulbs
BULBS
- globose underground stems with thin, papery
leaves on its surface - gladiolus (Gladiolus hybrids)
- gabi (Colocasia esculenta)
CORMS
EXTERNAL STRUCTURES OF STEMS
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
- at the end of the stem
TERMINAL OR APICAL BUD
- at the upper angle formed by the leaf stalk and
the stem called the leaf axil
LATERAL OR AXILLARY BUDY
- beside and above the axillary bud
ACCESSORY OR SUPERNUMERARY BUD
- on other parts of the plant such as leaves,
roots, or internodes
ADVENTITIOUS BUD
- the apical meristem shows three distinct
regions of meristematic activity
INTERNAL STRUCTURE OF THE STEMS
- develops into epidermis
GROUND MERISTEM - develops into cortex
PROTODERM
- develops into primary vascular tissues (xylem
and phloem)
PROCAMBIUM
- One cell layer derived from the protoderm
composed of cells with thick walls and covered
by a layer of cutin
EPIDERMIS
- A middle region composed of an outer zone of
collenchyma, an inner zone of parenchyma
and a layer of endodermis consisting of thick
walled cells
CORTEX
- An inner region composed of primary vascular tissue made up of primary xylem and primary phloem
*Xylem and phloem are arranged in cylinders
STELE OR VASCULAR CYLINDER
Inner portion
xylem
Outer portion
phloem
Each vascular bundle is called
fascicles
the whole circle.
Vascular cylinder
Each fascicle is surrounded by the _____
bundle
sheath composed is of
sclerenchyma and
collenchyma
The middle portion
pith
cambium outside
fascile
Interfascicular cambium
cambium inside fascile
Fascicular cambium
scattered bundles of
xylem and phloem, they are numerous at the
periphery of the stem
Vascular tissues
on the inner side of
the bundle and
xylem
on the outer side of the
bundle
phloem
-Vascular tissues are scattered bundles of
xylem and phloem, they are numerous at the
periphery of the stem
- Xylem and phloem NEVER form continuous
cylinders of tissues - xylem on the inner side of
the bundle and phloem on the outer side of the
bundle
-Cambium - ABSENT
Greater part of stem consists of parenchyma
tissue
* Vascular bundles are usually surrounded by
sclerenchyma and collenchyma cells for
support
HERBACEOUS MONOCOT STEM
Greater part of stem consists of __________
parenchyma
tissue
usually surrounded by
sclerenchyma and collenchyma cells for
support
Vascular bundles
- Derived from the vascular cambium
SECONDARY VASCULAR TISSUES
- Consisting of phellem (cork), phellogen (cork cambium), and phelloderm (secondary parenchyma)
PERIDERM
originates from the epidermis or
a layer of cells in the cortex which will give rise
to the inner phelloderm and outer phellem
Cork cambium
TWO DISTINCT REGIONS OF AN OLD WOODY STEM
BARK
WOOD
All tissues external to the vascular cambium
BARK
- Composed of the xylem
- Inside the vascular cambium
WOOD
- lighter, outer region which represents the
newly formed xylem for the conduction of water
and inorganic salts - alive
SAPWOOD
- darker, inner region and no longer able to
conduct materials because its tracheary
elements have been clogged with waste
products - dead
- old xylem
HEARTWOOD
- Provides mechanical support for leaves and
other plant organs - Conducts water, mineral salts and
manufactured food - Produces new living tissues
FUNCTIONS OF THE STEM
center of tissues; mass of parenchyma cells
Pith
holes in the vessels, tracheids
Pit
