The origin of the secondary plant body and the periderm
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The origin of the secondary plant body and the periderm
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SPECIMENS TECHNIQUES :3, 7, 8, 9
*Bidens pilosa TS stem.Mature Helianthus stem*Chrysanthemum TS stem. *Helianthus TS root
DEMONSTRATIONS:‑. *Bougainvillaea TS stem. Beta vulgaris TS stem. *Prunus TS woody stem. Beta TS root. Quercus - two and four-year-old stem, TS
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Chrysanthemum stemTS vascular bundle
protoxylem
metaxylem
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Chrysanthemum stem
metaxylem vessel
metaxylem tracheids
secondary xylem
vascular cambium
secondary phloem
primary phloemsieve elementcompanion cell
starch sheath
primary phloem fibres
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epidermis
outer cortex collenchymatous
primary phloem fibers
primary phloem
fascicular cambium
interfascicular cambium
Helianthus TS young stem. end of primary growth
metaxylem
protoxylem
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Helianthus: secondary growth
secondary growth is limitedto a narrow band within the vascular bundle
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Sugar beet stem
Included bundle
protoxylem
metaxylem
phloem
epidermis
outer cortex: collenchyma
starch sheath
Ground parenchyma
In the root, these included bundles form new secondary vascular tissue, and grow anomalously
phloem
metaxylem
protoxylem
The root
inner cortex: parenchyma
Secondary xylem
cambium
px
mx
cambium
.
ANOMALOUS GROWTH
included phloem
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Bougainvillaea stem
vascular cambium, producingsecondary phloem (exarch) and secondary xylem (endarch)
Bougainvillaea shows anomalous secondary growth. Note primary vascular bundles embedded withinthe stele.
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Bougainvillaea TS stem
primary vascular bundle
secondary xylem
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Sugar beet (Beta) root
multiple cambia, secondary vascular bundles and embedded primary vascular bundles. This is an anomalous structure
secondaryvascular bundle
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Oak (Quercus) stem
secondary xylem
secondary phloem
secondary phloemfibers and sclerieds
periderm
cambium
primary ray
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Oak stem, Periderm and lenticels
lenticel
secondary phloem fibres
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The cambium, Quercus stem
vascular cambium
secondary phloem
secondary xylem
companion cell
primary ray
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Sunflower (Helianthus) root
primary xylem
secondary xylemformation is notcontinuous