The origin of the secondary plant body and the periderm

SPECIMENS

TECHNIQUES :3, 7, 8, 9 .

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.

.

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DEMONSTRATIONS: * *

*Bidens pilosa TS

stem.

Mature Helianthus stem

*Chrysanthemum TS *Helianthus TS root

stem.

Bougainvillaea TS

Beta vulgaris TS

Prunus TS

Beta TS Quercus root

stem

stem

woody stem

- two and four-year-old stem, TS

Chrysanthemum

TS vascular bundle stem metaxylem protoxylem

Chrysanthemum

stem

starch sheath primary phloem fibres primary phloem sieve element companion cell secondary phloem vascular cambium secondary xylem metaxylem vessel metaxylem tracheids

Helianthus

TS young stem. end of primary growth epidermis outer cortex collenchymatous primary phloem fibers primary phloem fascicular cambium metaxylem protoxylem interfascicular cambium

Helianthus:

secondary growth secondary growth is limited to a narrow band within the vascular bundle

Sugar beet stem

epidermis outer cortex: collenchyma inner cortex: parenchyma starch sheath phloem Secondary xylem metaxylem

The root

protoxylem .

px mx cambium In the root, these included bundles form new secondary vascular tissue, and grow anomalously Included bundle

ANOMALOUS GROWTH

cambium included phloem phloem metaxylem protoxylem Ground parenchyma

Bougainvillaea

stem

vascular cambium, producing secondary phloem (exarch) and secondary xylem (endarch) Bougainvillaea shows anomalous secondary growth. Note primary vascular bundles embedded within the stele.

Bougainvillaea

TS

stem

primary vascular bundle secondary xylem

Sugar beet

(Beta)

root

multiple cambia, secondary vascular bundles and embedded primary vascular bundles. This is an anomalous structure secondary vascular bundle

Oak (

Quercus

) stem

periderm secondary phloem fibers and sclerieds secondary phloem cambium primary ray secondary xylem

Oak stem, Periderm

and

lenticels

lenticel secondary phloem fibres

The cambium,

Quercus

stem

primary ray companion cell secondary phloem vascular cambium secondary xylem

Sunflower (

Helianthus

) root

secondary xylem formation is not continuous primary xylem