Plant Organs Stems Flashcards
stem functions
• support
• conduct
• produce new living tissues
protective outer layer
covered by water conserving cuticle
epidermis
• xylem conducts water and dissolved minerals
• phloem conducts dissolved carbohydrates (sucrose)
vascular tissues
• cortex and pith
• ground tissue
storage tissues
have vascular bundles arranged in a circle (in cross section)
have a distinct cortex and pith
herbaceous eudicot stems
have scattered vascular bundles
have ground tissue instead of distinct cortex and pith
monocot stems
unlike roots, stems have
nodes & internodes, leaves and buds
unlike stems, roots have
root caps and root hairs
area on a stem where one or more leaves is attached
node
stem area between 2 successive nodes
internode
undeveloped shoot that contains an embryonic meristem
bud
a tip of stem
terminal bud
on side of stem
axillary bud
lateral meristem that produces secondary xylem (wood) to the inside and secondary phloem (inner bark) to the outside
Primary growth: Eudicot
vascular cambium
occurs in woody eudicots and conifers
produced by vascular cambium
not initially a solid cylinder of cells becomes continuous when production of secondary tissues begins
secondary growth: eudicot
certain parenchyma cells between bundles
retain ability to divide
connect to vascular cambium cells in each vascular bundle
form a complete ring of vascular cambium
secondary growth: eudicot
lateral meristem that produces cork parenchyma to the inside and cork cells to the outside
cork cambium
types of woody stem
• trees
• shrubs
contains conspicuous trunks
trees
produced branches from or near the ground
shrubs
variation of bark: bark is deeply fissured
bur oak (Quercus macrocarpa)
variation of bark: has a rough, shaggy bark
Shagbark hickory (Carya Ovata)
variation of bark: scaly
Norway Pine (Pinus resinosa)
variation of bark: has a peeling bark
Paper Birch (Betula papyrifera)
as stem thickens from secondary growth the epidermis including the stomata that allowed gas exchange for the herbaceous stem, dies. Stomata are replaced by _______
lenticels
completing their life cycle in one growing season
annuals
lower part of the stem often modified for food storage persist after the first growing season and bears buds from which an erect stem arises during the second growing season
biennial
short stem may produce new shoots for many years
perennial
functional secondary xylem
younger, lighter colored wood closest to the bark
sapwood
• older wood in the center of the trunk
• typically brownish red
• no longer functions in conduction
• denser than sapwood
• provides structural support for trees
• more resistant to decay
heartwood
can accurately determine the age of a wood sample by using a computer to match its ring to master chronnology
tree-ring dating
week stemmed plants that depend on other plants for support
plant with long, thin, often climbing stem
vine
types of modified stems
• rhizome
• tuber
• bulb
• corm
• stolon
horizontal underground stem that often serves as a storage organ and a means of sexual reproduction
rhizome
example: iris
the thickened end of a rhizome that is fleshy and enlarged for food storage
tuber
example: white potato
rounded, fleshy underground bud that consists of a short stem with fleshy leaves
bulb
example: onion
a short thickened underground stem specialized for food storage and asexual reproduction
corm
example: crocus
an aerial horizontal stem with long internodes; often forms buds that develop into separate plants
stolon
example: strawberry
significance of stem
• food & cooking materials
• medicine
• construction material
• condiments
• furnitures, toys, aesthetics
• scents and perfumes
• hair dyes
• paper
• clothing
• art materials
temporary or permanent clearance of large expenses of forests for agriculture or other uses
deforestation
