UEC Senior 1 Biology 独中高一生物

1. 4.1.2 Plant tissues

2. Pre-reading Quiz
• Which of the following is not a type of plant tissue?
A. Epithelial tissue
B. Epidermis tissue
C. Shoot meristem tissue
D. Vascular cambium tissue

3. Why do we study plant
tissue?
• Plants have impressive diversity,
specialized structure, and biochemical
attributes.
• The histology of plant structure allows
us to understand how plants acclimate
适应 to the environment and what are
the factors that determine variations in
plant form follow.
• Types and organizations of tissues can
provide insight into speciation and the
phylogeny of plant groups.

4. Common themes in the
structure of plants
• Physical forces do impose limits on cell
sizes and shapes, hence there are only a
limited type of tissue though they may
looked different.
• Plant needs tissues to support as they
grow stems, branches with leaves or erect
reproductive structures with flowers.
• Most plants require tissues for transport,
to move water and nutrients from one
plant part to another.
Xylem cell types.

5. Types of plant tissue
• Plant tissues can be divided into
five main types based on their
morphological structure and
physiological functions:
• meristematic tissue
• protective tissue
• parenchyma tissue
• mechanical tissue
• conductive tissue

6. 4.1.2.1
Meristematic
tissue

7. Meristematic tissue 分生组织
• Tissue that contains undifferentiated meristematic
cells分生细胞.
• Meristematic cells can divide rapidly through mitosis
有丝分裂 and they are indeterminate cells that are
not specialized yet.
• Meristem cells are small, thin-walled, closely
arranged, have relatively large nucleus, dense
cytoplasm and generally no vacuoles.
• Meristem are found in zones of the plant where
growth can take place.
Root meristem of onion.

8. Types of meristem
Based on the
location of
meristematic tissues
in plants, it can be
divided into:
• Primary (apical)
meristem 初生分
生组织/顶端分生
组织
• Secondary (lateral)
meristem 次生分
生组织

9. Primary and secondary growth
The increase in the
length of the shoot and
the roots
The increase in the
thickness or the girth of
the plant
Primary Growth
Secondary Growth

10. Primary (apical) meristem
• It is located at the tip of the roots and the shoots of plants.
• The root apical meristems give rise to future roots.
• The shoot apical meristems give rise to flower, fruit, leaf and stem.

11. Secondary (lateral) meristem
• It is located at the lateral side of roots and
stems and occurs as cylinders in older parts
of stem.
• It causes lateral growth (increase in
diameter)
• It includes the vascular cambium 维管束形
成层 and cork cambium 木栓形成层.
• Vascular cambium produces secondary
xylem 次生木质部 and secondary phloem
次生韧皮部.
• Cork cambium forms new layers of
protective tissue (periderm) on top of the
thicken surfaces of roots and shoots.
• Not all plants undergoes secondary growth.

12. What will happen?
SAM

13. Quiz
• Primary growth in plants is initiated by the
A) apical meristems
B) vascular cambium
C) lateral meristems
D) ground tissue
E) dermal tissue

14. Conclusion

15. 4.1.2.2 Protective tissue

16. Protective tissue
• It covers the outermost surface of plant
body for protection.
• Its cells are closely arranged, flattened
and irregular in shape, lack of
chloroplast and with thick cell wall.
• Its function is to reduce the loss of
water through transpiration, to prevent
invasion of diseases caused by
pathogens and mechanical injury etc.
• Examples: epidermal tissue, periderm
(form by the cork cambium) and cork.
Root hair is an extension of root
epidermal cells.
Periderm (yellow) of a stem
under light microscope (10x).
保护组织

17. Epidermal tissue
Top: The epidermal tissue on the abaxial side of the leaf:
epidermal cells, guard cells, subsidiary cells, and epidermal
hairs (trichomes 毛茸).
Left: Root hair as an extension of root epidermal cell/
• Greek ἐπιδερμίς, meaning “over-skin”
• A single layer of cells that covers the
leaves, flowers, roots and stems.
• Functions:
• Forms a boundary between the plant and
the external environment.
• Protects against water loss
• Regulates gas exchange
• Secretes metabolic compounds
• Absorbs water and mineral nutrients (roots)
trichomes
Guard cells around
stroma & pavement cells
表皮

18. Periderm and cork
• Periderm 周皮 includes cork 木栓
层, the cork cambium木栓形成层
(and the phelloderm 栓内层).
• Periderm is only found in plants
with secondary growth.
• Cork is an external, secondary
tissue that is impermeable to
water and gases.
• Function of cork:
• protects the stem against water loss
• Protects the invasion of insects into
the stem
• prevents infections by bacteria and
fungal spores

19. Quiz
• Which of the following is not a kind of epidermal cell or part of an
epidermal cell?
A) trichome
B) root hair
C) guard cell
D) cork

20. Conclusion
• Protective tissue covers the outermost surface of plant body for
protection.
• Its cells are closely arranged, flattened and irregular in shape, lack of
chloroplast and with thick cell wall.
• Its functions are to reduce the loss of water through transpiration, to
prevent invasion of diseases caused by pathogens and mechanical
injury etc.
• Epidermal tissue is found in all parts of the plant cells.
• Periderm, differentiated from the cork cambium, replace epidermal
tissue in plants with secondary growth.

21. 4.1.2.3 Parenchyma tissue

22. Supporting tissue or
Packing tissue
• Parenchyma is the least specialised cell
types found in all organs of a plant.
• Greek word para meaning "beside",
chyma meaning "in filling
• Its cells are large, with relatively thin
primary cell walls and a large central
vacuole.
• The cells are loosely packed together
with large intercellular air spaces to allow
exchange of gases.
• Parenchyma cells can be found in the
ground tissue of pith and epidermal in
stems and roots, leaves, flowers and
many fruits and seeds.
薄壁組織

23. Functions of parenchyma tissue
• Wound repair and the potential for
renewed meristematic activity
• Photosynthesis (mesophyll
cells/chlorenchyma cells = parenchyma
cells with chloroplasts)
• The exchange of gases (guard cells)
• Storage of starch, protein, fats, oils and
water in roots, tubers (e.g. potatoes), seed
endosperm (e.g. cereals) and cotyledons
(e.g. pulses and peanuts)
• Secretion (e.g. the parenchyma cells lining
the inside of resin ducts)
• Aeration that provides buoyancy and helps
aquatic plants in floating (aerenchyma)

24. 4.1.2.4 Mechanical tissues

25. Mechanical tissues
• Mechanical tissue is the tissue to support the plant body.
厚角組織 厚壁組織

26. Collenchyma tissue
• Collenchyma tissue consists of living
elongated cells with irregularly
thickened walls.
• Collenchyma cells have only a thick
primary cell wall made up of cellulose
and pectin, with thickenings at the
corners of the cells.
• They provide structural support,
particularly in growing shoots and
leaves, and may be the main
supportive tissue for some herbaceous
plants.
厚角組織

27. Sclerenchyma tissue
• Sclerenchyma cells are the principal
supporting cells in plant tissues that have
ceased elongation.
• Sclerenchyma has thick secondary cell walls
which are completely lignified 木质化.
• The cell wall is impermeable to water, solutes
and gases, although pits are present in the cell
walls.
• When the cells are maturing, lignin 木质素 is
deposited gradually on the walls.
• At maturity, they contain no living protoplast,
i.e. they are dead at maturity.
• Sclerenchyma can be divided into fibres and
sclereids.
Lignin in sclerenchyma can be stained red with
safranin or phloroglucinol-hydrochloric acid.
厚壁組織

28. Fibre
• Fibers or bast are generally long,
slender, usually occurring in strands or
bundles.
• Fibres are mainly found in the roots
and the stems of plants.
• For example in stems of flax 亚麻,
hemp 麻 and jute 黄麻.
纖維細胞
Flax, hemp, and jute

29. Sclereids
• Sclereids are often found in the fruits
and the seeds of plants (though they
may be found in leaves as well).
• These are relatively short and generally
have a shape of a star.
• Sclereids protect other cells.
• For example, sclereids can be found as
white and hard granules in the pericarp
of pear, cores of apples.
石细胞

30. Quiz
A
B
C

31. Summary

32. Quiz
• Plants grow throughout their entire lives because of ______ that
continues to divide.
A) vascular tissue
B) dermal tissue
C) meristem tissue
D) ground tissue

33. Quiz
• Which of the following cells protect the inner body parts and prevent
the plant from drying out?
A) epidermal cells
B) parenchymal cell
C) sclerenchymal cell
D) sieve-tube cell
E) tracheid cell

34. Quiz
• Which of the following cells are relatively unspecialized and
correspond best to the generalized plant cell?
A) epidermal cells
B) parenchymal cell
C) sclerenchymal cell
D) sieve-tube cell
E) tracheid cell

35. 4.1.2.5
Vascular tissue

36. Conductive tissue
• Conductive tissue is also known
as the vascular tissue.
• It is a compound tissue which is
composed of several types of
cells.
• It can be divided into xylem and
phloem.
Cross-section of a leaf.
输导组织
维管组织
木质部韧皮部

37. Xylem
• derived from the Greek word ξύλον (xylon)
"wood"
• Xylem transports water and inorganic salts from
the roots to other parts of the plants.
• The movement of water is unidirectional.
• Xylem consists of three different types of cells:
xylem parenchyma cells and xylem fiber cells, and
the tracheary elements (TE).
• The TE are completely dead at maturity, and act
like pipes.
• The TE have a thick, strengthened cellulose cell
wall with a hollow lumen.
• There are two types of tracheary elements: vessel
elements and tracheids.
• Tracheids are longer.
• Vessel elements are shorter, and are connected
together into long tubes that are called vessels.
• Parenchyma cells store water, mineral nutrients
and carbohydrates, and respond to wounding.
• Fibers provide structural support.

38. Phloem
• derived from the Greek word φλοιός
(phloios) "bark".
• Phloem transport organic nutrients made
during photosynthesis (photosynthate) to all
parts of the plant where needed.
• The movement of photosynthate can be
bidirectional, but mostly are from source
tissues (eg. mesophyll cells) to sink tissues
(eg. non-photosynthetic cells).
• Phloem is composed of several cell types
including sclerenchyma, parenchyma, sieve
elements.
• Sieve element conducts the photosynthate.
• Parenchyma cells carried out metabolic
functions helps transfer materials between
phloem and other tissues.
• Sclerenchyma such as fibres and sclereids
provide structural support.

40. Quiz
• Xylem and phloem belong to the ______ tissue system.
A) dermal
B) ground
C) vascular

41. Quiz
• Which of the following cells are hollow and nonliving at maturity?
A) epidermal cell
B) parenchymal cell
C) tracheid
D) sieve-tube cell
E) companion cell