Primary and secondary growth

definations of the terms; growth, development, meristems, primary and secondary growth with their explanations

1. TOPICAL TOPICAL
PRESENTATIONS ON PRESENTATIONS ON
GROWTH AND GROWTH AND
DEVELOPMENTDEVELOPMENT
Feb 01, 2017.Feb 01, 2017.
@ UNIK BIOLOGY LAB
TOPIC ONE: Primary and secondary growth
in plants using Arabidopsis thaliana as a
model plant.
By Mr. Orache Francis 15BSCED1154

2. Arabidopsis thaliana plantArabidopsis thaliana plant

3. Arabidopsis thalianaArabidopsis thaliana

4. Overview Overview
Definations of the terms, growth,
development, primary growth, and
finally growth.
Meristems ( apical and lateral
meristems)
Primary growth in details.
Secondary growth in details
Annual rings

5. Defination of terms..Defination of terms..
Growth simply refers to the
permanent increase in size of an
organism.
Development is the increase in
complexity of an organism.
Primary growth is the increase in
length of a plant.
Secondary growth is the increase in
girth of a plant.

6. Meristems Meristems
Meristematic tissues are clumps of
small cells with dense cytoplasm
and proportionately large nuclei.
Meristem is a type of plant tissue
consisting of undifferentiated cells
that can continue to divide and
differentiate.

7. Meristems Meristems
Apical meristems
located at tip of stems and roots
Plant tissues that result from
primary growth are called primary
tissues.
make up primary plant body
root apical meristem protected by
root cap

8. Meristems Meristems

9. Lateral meristemsLateral meristems
Most trees, shrubs, and some herbs
have active lateral meristems.
increases girth in nonwoody plants -
secondary growth
Woody stems
cork cambium
produces cork cells
vascular cambium
produces secondary vascular tissue

10. Meristems Meristems

11. Primary and secondary growthPrimary and secondary growth
Primary growth results from cell
division at the apical meristem at
the plant tip.
Secondary growth results from cell
division at the lateral meristem,
increasing the shoot’s girth.

12. Primary growth in plantsPrimary growth in plants
Primary growth is the upward
growth of the stem and the
downward growth of the roots. It is
the type of growth that makes a
plant longer.

13. Primary growthPrimary growth
Most primary growth occurs at the
apices, or tips, of stems and roots.
Primary growth is a result of rapidly-
dividing cells in the apical
meristems at the shoot tip and root
tip.

14. Primary growthPrimary growth
 Subsequent cell elongation also
contributes to primary growth. The
growth of shoots and roots during
primary growth enables plants to
continuously seek water (roots) or
sunlight (shoots).

15. Primary growthPrimary growth
Zone of cell division
cells divide every 12 to 36 hours
toward the edges of the concave
dome
Apical meristem daughter cells
divide into protoderm, procambium,
and ground meristem tissues.
Zone of elongation
roots lengthen because cells
produced by primary meristems
grow longer than wide

16. Primary growthPrimary growth
Zone of maturation
cells differentiate into specific cell
types
root surface cells mature into
epidermal hairs, each with root hair
cortex produced by parenchyma
cells
inner boundary differentiates into
endodermis
surrounded by Casparian strips
composed of suberin

17. Primary growthPrimary growth

18. Secondary growthSecondary growth
The increase in stem thickness that
results from secondary growth is
due to the activity of the lateral
meristems, which are lacking in
herbaceous plants. Lateral
meristems include the vascular
cambium and, in woody plants, the
cork cambium .

19. Secondary growthSecondary growth
The vascular cambium is located just
outside the primary xylem and to the
interior of the primary phloem.

20. Secondary growthSecondary growth
The cells of the vascular cambium
divide and form secondary xylem
(tracheids and vessel elements) to
the inside and secondary phloem
(sieve elements and companion
cells) to the outside

21. Secondary growthSecondary growth
The thickening of the stem that
occurs in secondary growth is due
to the formation of secondary
phloem and secondary xylem by the
vascular cambium, plus the action of
cork cambium, which forms the
tough outermost layer of the stem.
The cells of the secondary xylem
contain lignin, which provides
hardiness and strength.

22. Secondary growthSecondary growth
In woody plants, cork cambium is
the outermost lateral meristem. It
produces cork cells (bark)
containing a waxy substance known
as suberin that can repel water. The
bark protects the plant against
physical damage and helps reduce
water loss.

23. Secondary growthSecondary growth
The cork cambium also produces a
layer of cells known as phelloderm,
which grows inward from the
cambium. The cork cambium, cork
cells, and phelloderm are
collectively termed the periderm.

24. Secondary growthSecondary growth
The periderm substitutes for the
epidermis in mature plants. In some
plants, the periderm has many
openings, known as lenticels, which
allow the interior cells to exchange
gases with the outside atmosphere .
This supplies oxygen to the living-
and metabolically-active cells of the
cortex, xylem, and phloem.

25. Secondary growthSecondary growth
After a long period of secondary
growth, two types of woods appear
in the stem such as, sapwood,
heartwood. Sapwood is recently
formed wood and heartwood is
earlier formed wood.

26. Secondary growthSecondary growth
In woody stems the stomata are
blocked by the presence of cork
cells
The epidermis of woody stems
breaks up to form tiny pores called
lenticels which allow gaseous
exchange.

27. Annual ringsAnnual rings
The activity of the vascular
cambium gives rise to annual growth
rings. During the spring growing
season, cells of the secondary
xylem have a large internal
diameter; their primary cell walls
are not extensively thickened.
This is known as early wood, or
spring wood.

28. Annual ringsAnnual rings
During the fall season, the
secondary xylem develops
thickened cell walls, forming late
wood, or autumn wood, which is
denser than early wood.

29. Annual ringsAnnual rings
This alternation of early and late
wood is due largely to a seasonal
decrease in the number of vessel
elements and a seasonal increase in
the number of tracheids. It results in
the formation of an annual ring,
which can be seen as a circular ring
in the cross section of the stem .

30. Annual ringsAnnual rings
An examination of the number of
annual rings and their nature (such
as their size and cell wall thickness)
can reveal the age of the tree and
the prevailing climatic conditions
during each season.

31. Topic one summaryTopic one summary
So my fellow students we’ve looked
at:
What growth and development mean
Meristems
Primary growth
Secondary growth, and finally
Annuall rings

32. Thank you for your kind Thank you for your kind
attentionattention
Your classmateYour classmate, ,
~ ~ Orache Francis~Orache Francis~
[phone] / [phone]
[email protected]
FACEBOOK: Orache Francis
Twitter: @Francis Orache

33. Before a bye-bye…….Before a bye-bye…….