The document provides a comprehensive overview of plant biology, covering characteristics, structures, reproduction methods, and processes such as photosynthesis. It discusses both flowering and non-flowering plants, detailing their anatomy including the shoot and root systems, the functions of various plant parts, and the mechanisms of reproduction through structures like cones and flowers. Additionally, it elaborates on photosynthesis as a vital biological process that converts light into organic compounds, emphasizing its importance in supporting life on Earth.

1. Unit two
plants

2. contents
2.1. Characteristics of plants
2.2. Non- flowering and flowering plants
2.3. Structure and function of plant parts
2.4. Reproduction in plant
2.4.1. Non-flowering
2.4.2. Flowering
2.4.3. Pollination

3. contents
2.5. Seeds (monocots, dicots)
2.6. Seed Dispersal and Germination
2.7. Photosynthesis
2.8. Transport in plants
2.9. Response in plants
2.10. Medicinal plants
2.11.Renowned Botanists in
Ethiopia

4. 2.1. Characteristics of plants

5. Characteristics of plants
 Plants are living things
 Like all living organisms plants can perform all the seven
characteristics of life.
 Plants are multicellular.
 Plants are made up of many cells with specialised function.
 Each cells are dependent in function with one another.
 Plants are autotrophic (self–feeding).
 Plant can make their own food from inorganic molcules in the
presence of sun light and chlorophyll.
 Plants are sessile
 plants can not move from place to place by themselves.
 Plants practice asexual and sexual reproduction patterns.
 They reproduce by both sexually and asexually

6. 2.3. Structure and function
of
plant parts

7. • the external structure of a typical angiosperm
has two major systems.
• The shoot system: This is the plant part
usually found above the ground and includes
the organs such as stem, branches, leaves,
buds, flowers and fruits.
• The root system: This is the part of the plant
that usually grows downward into the ground.
• It includes the primary or tap root, lateral or
branch roots, root hairs and root cap.

9. • The external structure
of a typical leaf consists
of the petiole (leaf
stalk), lamina (blade –
broadestpart), midrib,
margin, base and tips

10. A. Outer layer this is also known as the epidermis,
 a single layer of tightly packed cells that covers the upper and lower
surface of the leaf.
 The upper epidermis is usually covered by a waxy cuticle, The lower
epidermis usually contains beans shaped guard cells that leave ope n
spaces known as stomata (singular stoma).
B. Middle layer
 This is known as the mesophyll (“middle leaf”) layer. It lies between the
upper and lower epidermis.
 It includes tissues that are directly or indirectly involved in
photosynthesis.
 There are two regions in the mesophyll layer

11. The internal structure of a stem
• The epidermis is the outermost layer of the stem
• the cells are compactly arranged, which
in turn protect the underlying tissues from mechanical injury and prevent the
entry of harmful organisms
• Hypodermis lies below the epidermis. It is mainly composed of collencyma cells
that are specially thickened at the corners due to the deposition of thick cellulose
• Cortex consists of few layers of thin-walled, large, round, or oval
cells, having intercellular space and serving for storage of food.
Endodermis is the innermost layer of the cortex that separates the
cortex from the vascular bundles.
the endodermis serves as a
food reserve and may be termed as a starch sheath
Pith – occupies the central portion of the stem, composed of thin walled cells,
which are rounded or polygonal, with or without intercellular space. It stores food
and helps in the internal translocation
of water.

12. 2.3.3 The internal structure of a root
• Peliferous layer is the outermost layer made up of single-layer cells.
The cuticle is absent. . It consists the single-celled root hairs
• Cortex is a multi-layered large zone made of thin-walled oval or
rounded loosely arranged cells with intercellular spaces. It stores
food and water.
Endodermis is the innermost layer of the cortex, made of barrelshaped
closely packed cells. The layer helps the movement of water
and dissolved nutrients from the cortex into the xylem.
Pericycle is a single layer inner to endodermis. It is the site of origin
of lateral roots.
Vascular bundles consist of xylem and phloem with meristematic
(cambium) or actively dividing cells between them
Pith is present in young roots while absent in old roots

13. 2.4. Reproduction
in
plant

14. 2.4.Reproductio
n in plants

15. 2.4.1 reproduction in non flowering
plants
• Gymnosperms are a seed plant that produces
naked seeds(not enclosed by any protective
covering)
• Most have needlelike or scale like leaves
• Most have deep growing root systems
• Cones – reproductive structure for a gymnosperm
• In this lesson, you will learn the life cycle of
gymnosperm, using the pine tree as a typical
representative of conifers as well as
gymnosperms in general.

16. Types of cones
• Most gymnosperms produce two types of cones
Male cones
 smaller than female
cones
 produce pollen that later
become sperm
Female cones
 Larger than male
 Contain one ovule at the
base of each scale
 Ovule – structure that
contains egg cell

17. 2.4.2Reproduction in Flowering
Plants

18. Pollination
• Transfer of pollen from a
male reproductive structure
to a female reproductive
structure
– Wind often carries the pollen
• Pollen collects in the sticky
substance produced by each
ovule
• Scales of ovule close and
trap pollen
• Seed develops on scale

19. Flower
• Sexual reproductive structure
• Produces egg and sperm
• Fertilization takes place inside the flower

21. What is a flower?
• A flower is the reproductive part of a
flowering plant.
• They are modified leaves.
– Some have attractive colors and fragrances
– This is to attract pollinators

22. Complete Flower
• Has all 4 parts:
– Sepals – protects the developing bud
– Petals – attracts pollinators
– Stamens – male reproductive structure
– Pistil – female reproductive structure

23. Incomplete Flowers
• They do not have all of the principle parts
– Some flowers do not have a sepal and petals. For
example: the flower in wheat and oats.
– In some cases the female and male flower parts
are separate on plants.
– Both are needed to produce a seed

24. Perfect vs Imperfect
• Perfect flower: It has the stamen and the pistil
in the same flower
• An imperfect flower has the male sex organs
or the female sex organs, but not both on the
same flower

25. Monoecious vs Dioecious
• Plants may have both male and female
imperfect flowers on them.
• They are called monoecious plants
– Corn is a monoecious plant.
– Others include: Squash, melons and pumpkins
• Dioecious is when some plants have male
flowers and others have female flowers.
– Strawberries are dioecious
– Also, gourds and bradford pears

26. Pistil
*Stigma –top of the pistil,
Sticky surface for pollen to
stick to
*Style – connects the stigma
to the ovary
*Ovary –contains ovules
( eggs)
Stamen
*Anther – produces sperm
nuclei by meiosis. Sperm
nuclei are enclosed by
pollen grains.
*Filament – holds the anther
up
Female
reproductive
organ
Male
reproductive
organ

27. Pollination
• Transfer of mature pollen grains from the
anther to the stigma
• Pollination requires pollinating agents
such as insects or wind.
• There is a strong relationship between
the nature of the flower and the
pollinating agents.
-wind
-insects

28. Types of polenation
• The transfer can be
• Self Pollination;- between stamen and
pistil on one flower or between flowers
on one plant or
• cross-pollination between two flowers
on different plants .

30. What is a seed?
• Seeds are containers of new life.
– Seeds are formed in the ovaries of flowers, which
become fruit.
– Seeds ensure continuing life as well as provide
food and other products

31. Kinds of Seeds
• Monocot
– Monocots are plants that have a seed with one seed
leaf known as a cotyledon.
• The embryo in the seed will have one leaf.
• As the embryo grows, the leaves develop with parallel
venation.
– Corn, wheat, rice, all grasses
• Dicot
– Dicots are plants that have a seed with two
cotyledons.
• The embryo in the seed has two leaves.
• Leaves of a dicot have net venation.
– Tomatoes, beans, petunias, trees

32. Parts of a seed - Dicot
• Outside
– Seed coat
– Hilum
– Micropyle
• Inside
– Cotyledons
– Radicle
– Hypocotyl
– Epicotyl
– Plumule

33. SEED GERMINATION

36. DEFINITION
• Sum of events that begin with hydration of seeds
and culminate in emergence of the embryonic axis.
• In simple terms it is known as the breaking of
dormancy.

37. PHOTOSYNTHESIS
Life’s grand device

38.  Introduction
 Properties of light and
pigments
 Chloroplast structure and
function
 Light reactions
 “Dark” or Carbon reactions
 Summary and conclusions
Photosynthesis

39. Definition:-PHOTOSYNTHESIS
• From the Greek
PHOTO = light and SYNTHESIS = a whole made of parts
put together.
PHOTOSYNTHESIS is the process whereby plans, algae,
some bacteria, use the energy of the sun to synthesize
organic compounds (sugars) from inorganic compounds
(CO2 and water). Or
A plant biochemical process that involves making of
organic food and from inorganic molecules(CO2 andH2O)
in the presence of sun light and chlorophyll.

40. WHY IS PHOTOSYNTHESIS SO
IMPORTANT?
• PHOTOSYNTHESIS is one of the most important
biological process on earth!
• Provides the oxygen we breathe
• Consumes much of the CO2
• Food
• Energy
• Fibers and materials

41. GENERAL FORMULA FOR
PHOTOSYNTHESIS
light
6 CO2 + 12 H2O ---------> C6H12O6 + 6 O2 + 6 H2O
pigments, enzymes
• Oxygen on earth allowed for the evolution of aerobic
respiration and higher life-forms.
• Respiration: extracting energy from compounds (sugars)
C6H12O6 + O2  6 CO2 + ATP

42. GENERAL FORMULA FOR
PHOTOSYNTHESIS
light
6 CO2 + 12 H2O ---------> C6H12O6 + 6 O2 + 6 H2O
pigments, enzymes
• Oxygen on earth allowed for the evolution of aerobic
respiration and higher life-forms.
• Respiration: extracting energy from compounds (sugars)
C6H12O6 + O2  6 CO2 + ATP

43. II. PROPERTIES OF LIGHT
Virtually all life depends on it!
• Light moves in waves, in energy units
called PHOTONS
• Energy of a PHOTON inversely proportional
to its wavelength
• Visible light (between UV and IR) occurs in
a spectrum of colors

44. Visible light contains just the right amount of
energy for biological reactions

45. Light is absorbed by pigments
• The primary pigment for photosynthesis is
chlorophyll a
• It absorbs blue and red light, not green (green
light is reflected back!)
Absorption spectrum
of chlorophyll a

46. • Absorption spectrum of chlorophyll a:
BLUE & RED
• Action spectrum of photosynthesis closely
matches absorption spectrum of
chlorophyll a, but not perfectly (due to
accessory pigments)

47. Accessory pigments like chlorophyll b and
carotenoids (beta-carotene, lycopene):
• absorb light at different wavelengths,
(extending the absorption range)
• help transfer some energy to chlorophyll a
• protect cell from harmful byproducts

48. Chlorophyll a is the primary
photosynthetic pigment that drives
photosynthesis.
Accessory pigments absorb at
different wavelengths,
extending the range of light
useful for photosynthesis.

49. Where does photosynthesis occur?

50. Chloroplast structure
• Football shaped
• Double membrane
• Stroma
• Thylakoid
membrane
• Grana (stacks)
• Lumen
(inside thylakoid)
stroma
Grana
thylakoids
lumen

51. Inside a Chloroplast
• Remember: Structure correlates to function!

52. Overview of photosynthesis:
Note: The Light and “Dark” or Carbon
reactions happen at different sites in the
chloroplast
LIGHT
REACTIONS
(Thylakoids)
“DARK” or CARBON
REACTIONS
(Stroma)
light
ATP
NADPH
(ENERGY)
H2O
O2
(OXYGEN GAS)
CO2
C6H12O6
(GLUCOSE)

53. 2.8.
Transport
in
plants