stems by pooja
TRANSCRIPT
![Page 1: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/1.jpg)
Prepared by:Pooja KhanparaAPIP, Jamnagar
STEMS
![Page 2: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/2.jpg)
STEMS• Origin• Functions • External Anatomy • Internal Anatomy • Specialized
Stems
![Page 3: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/3.jpg)
Origin
First stem of a plant develops from part of a seed embryo called epicotyl, w/c is a continuation of the hypocotyl
![Page 4: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/4.jpg)
The Plant Body: StemsFUNCTIONS OF STEMS• Produces & support appendages
of plant (leaves, flowers, fruits) • transport water and solutes
between roots and leaves. • Stems in some plants are
photosynthetic.• Produce & store materials
necessary for life (e.g., water, starch, sugar).
• In some plants, stems have become adapted for specialized functions.
![Page 5: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/5.jpg)
Stems support a display of leaves.
Stems orient the leaves toward the light with minimal overlap among the leaves.
![Page 6: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/6.jpg)
The stem supports a display of flowers
![Page 7: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/7.jpg)
The stem does photosynthesis…
and stores water.
Opuntia-prickly pear
![Page 8: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/8.jpg)
This stem does photosynthesis, stores water, but also produces a defense chemical: mescaline…a hallucinogen.
Lophophora williamsii - peyote
![Page 9: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/9.jpg)
Two Types of Aerial Stems
Herbaceous Stems Woody Stems
Soft & greenLittle growth in diameterTissues chiefly primaryChiefly annualCovered by epidermisBuds mostly naked
Tough & not greenConsiderable growth in
diameterTissues chiefly secondaryChiefly perennialCovered by corky barkBuds chiefly covered by
scales
![Page 10: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/10.jpg)
Herbaceous Stem woody stem
![Page 11: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/11.jpg)
EXTERNAL ANATOMY
![Page 12: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/12.jpg)
![Page 13: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/13.jpg)
STEM APICAL MERISTEM
![Page 14: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/14.jpg)
![Page 15: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/15.jpg)
![Page 16: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/16.jpg)
![Page 17: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/17.jpg)
PRIMARY & SECONDARY GROWTH
![Page 18: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/18.jpg)
Apical DominanceApical dominance refers
to the suppression of growth by hormones produced in the apical meristem.
Lateral branch growth are inhibited near the shoot apex, but less so farther from the tip.
Apical dominance is disrupted in some plants by removing the shoot tip, causing the plant to become bushy(thick).
![Page 19: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/19.jpg)
INTERNAL STEM ANATOMY
![Page 20: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/20.jpg)
Monocotyledonous & Dicotyledonous Flowering Plants
![Page 21: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/21.jpg)
Monocot Stem – cross section
![Page 22: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/22.jpg)
Typical Stem Cross Section (Dicot Stem)
Helianthus annuus-sun flower annual
Pith
A ring of vascular bundles
Epidermis
Cortex
![Page 23: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/23.jpg)
Epidermis - window, reduce water loss
Cortex Collenchyma- extensible support
Cortex Parenchyma- photosynthesis, etc.
Fibers- rigid support
Functional Phloem- conduct sugars etc. away
from leaf to rest of plantVascular Cambium- adds 2° xylem and 2° phloem
Xylem-conduct water and minerals
up from soilPith
-water storage, defense?
![Page 24: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/24.jpg)
VIP Stem: Provide both name and function labels:
outside
to center
Epidermis: reduce evaporation, gas exchange
Cortex: photosynthesis, collenchyma support
Vascular Bundles: conduction
Pith: water storage? defense? disintegrate?
Vascular Bundle:
Phloem Fibers: support
Functional Phloem: conduct CH2O away from leaf
Vascular Cambium: add 2° Xylem and 2° Phloem
Xylem: conduct minerals up from soil
outs
ide
to c
ente
r
![Page 25: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/25.jpg)
Vitis vinifera - grape
![Page 26: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/26.jpg)
Vitis vinifera - grape
Notice how the vascular cambia of adjacent vascular bundles line up side by side.
Notice that cambium tissue differentiates between the bundles, connecting the cambia together.
Remnants of the procambium:Intrafasicular cambium Interfasicular cambium
![Page 27: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/27.jpg)
Vitis vinifera - grapeThe vascular cambium makes 2° tissues:
2° phloem2° xylem
![Page 28: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/28.jpg)
Basswood – 1 & 2 years old
![Page 29: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/29.jpg)
Three years of Secondary Growth
Tilia - basswood
SecondaryXylem
Secondary Phloemcambium
![Page 30: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/30.jpg)
A cork cambium differentiates and produces a periderm.
Epidermis
Cork Cambium
Phelloderm
cutin
suberin
Cork Cells
![Page 31: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/31.jpg)
Over time, the epidermis dies.
The cork cells build up to for a thick layer for the bark of a tree. We use this to make stoppers for wine bottles and so on.
When suberin is fully developed, the cortex cells will eventually be in the dark. So these chloroplasts will lose their function!
![Page 32: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/32.jpg)
Bark =
epidermis + periderm +
cortex + phloem + vascular
cambium
Wood =
secondary xylem only!
Pith =
a small percentage of tree diameter
at maturity
![Page 33: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/33.jpg)
Anatomy of a Woody Stem
![Page 34: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/34.jpg)
Sequoia sempervirens - giant sequoia
The trees pictured below have long lost their epidermis on the woody portion of the stem
![Page 35: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/35.jpg)
The study of the growth rings in wood: Dendrochronology
![Page 36: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/36.jpg)
Each year the cambium produces a layer of secondary xylem and a layer of secondary phloem.
This photo shows secondary xylem from parts of three years in Pinus strobus (white pine).
mid-summer of one year
fall of that yearwinter of that year
spring of the next year
![Page 37: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/37.jpg)
StemsStems—the axes of plants—consist of nodes (where leaves and axillary buds are produced) separated by internodes.
![Page 38: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/38.jpg)
Node - region of the stem where the leaf and bud are borne.
Internode - the part of the stem between two adjacent nodes.
Herbaceous - not woody; dying down at the end of the growing season.
Woody - hard in texture, containing secondary xylem, and persisting more than one growing season.
Acaulescent - having an inconspicuous stem.
Caulescent - having a distinct stem.
![Page 39: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/39.jpg)
Modified & Specialized Stems
![Page 40: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/40.jpg)
Bulbs• Bulbs - large buds
with a small stem at the lower end surrounded by numerous fleshy leaves that store nutrients; adventitious roots at base
• Eg. onion, tulip, hyacinth, daffodil and lily
![Page 41: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/41.jpg)
Corms• Corms - resemble
bulbs but composed entirely of stem tissue surrounded by a few papery scale like leaves, food storage organs with adventitious roots at the base of corms
• Eg. crocus and gladiolus.
![Page 42: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/42.jpg)
Rhizomes
• Rhizomes - horizontal stems that grow below the ground with adventitious roots
• Eg. irises, ferns, and grasses.
![Page 43: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/43.jpg)
Cladophylls
•Cladophylls or cladodes - leaf-like stems modified for photosynthesis
•Eg. butcher's broom, asparagus, orchids (eg. Epidendrum)
![Page 44: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/44.jpg)
Succulent Stems
• Succulent stems - stout fleshy stems that are modified for water and food storage
Eg. cacti
![Page 45: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/45.jpg)
![Page 46: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/46.jpg)
Thorns- for protection from grazing animals
• Bougainvillea
• Honey locust (modified stem)
• Black Locust (modified leaf stipules)
![Page 47: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/47.jpg)
Food Storage StemsPrickly Pear Cactus
Bamboo Shoots Kohlrabi
![Page 48: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/48.jpg)
Food Storage Stems - Sugarcane
![Page 49: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/49.jpg)
Tubers
• Tubers – swollen regions of stems that store food for subsequent growth
• The "eyes" of a potato (irish potatoes Solanum tuberosum) are the nodes of a starch-ladened stem
![Page 50: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/50.jpg)
Stolons
• Stolons or runners - horizontal stem that grow above the ground with long internodes
Eg. Bermuda grass
(Cynodon dactylon)
Spider plant (Chlorophytum)
Fern (Nephrolepis)
Bermuda grass (Cynodon dactylon).
![Page 51: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/51.jpg)
Rosette• Rosette - stem with short internodes and leaves
attached at nodes
![Page 52: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/52.jpg)
Wild Radish – Rosette & BoltWild Radish – Rosette & Bolt
YEAR ONEYEAR ONE YEAR ONEYEAR ONE
A FLOWERING ANNUALA FLOWERING ANNUAL
![Page 53: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/53.jpg)
Common Mullen – Rosette & BoltCommon Mullen – Rosette & Bolt
YEAR ONEYEAR ONE
YEAR TWOYEAR TWO
A FLOWERING BIENNIALA FLOWERING BIENNIAL
![Page 54: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/54.jpg)
Buds
Buds are short embryonic stems. In angiosperms they are found at the nodes, in the leaf axil (the angle formed by the stem and the petiole of the leaf).
Axillary bud - a bud located in the leaf axil.Terminal bud - a bud at the apex of a stem.
![Page 55: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/55.jpg)
PHYSIOLOGY OF STEMS
• Conduction of Materials by Xylem1) Root pressure – powered by transpiration of water from the leaves
2) Transpiration pull and water cohesion – water is pulled up from the roots due to adhesion of water to the xylem walls & tension generated by the water-potential gradient bet. leaves & xylem
Other contributing factors:3) Atmospheric pressure
4) Action of Living cells 5) Imbibition in cell walls of xylem 6) Capillary attraction
![Page 56: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/56.jpg)
PHYSIOLOGY OF STEMS
• Conduction of Materials by Phloem - nutrient-rich fluid in the phloem moves from areas of high
solute concentration & water pressure to areas of low solute concentration & water pressure
• Hypotheses of phloem function are:1) cytoplasmic streaming2) movement through interface3) pressure flow or mass flow
![Page 57: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/57.jpg)
Transpiration-Cohesion Hypothesis for Water Movement
![Page 58: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/58.jpg)
Sugar Loading of Phloem and Bulk Flow
![Page 59: Stems by pooja](https://reader034.vdocument.in/reader034/viewer/2022051318/5a650e987f8b9aa6218b49b9/html5/thumbnails/59.jpg)
Sugar Loading of Phloem and Bulk Flow