1. Selected Plant Topics
Chapters 23 – 25

2. Specialized Tissues
in Plants
23 -1

3. Seed Plant Structure
• Three of the principal organs of
seed plants are roots, stems, and
leaves

4. Roots
• Absorb water and dissolved
nutrients
• Anchor plants in the ground
• Hold soil into place and prevent
erosion

8. Stems
• Support above ground parts of plant
• Transports nutrients

9. Leaves
• Main photosynthetic systems
• Let in oxygen and carbon dioxide

10. Vascular Tissue
• Forms a transport system that
moves water and nutrients
throughout the plant

11. Types of vascular tissue
• Xylem – brings water and
nutrients up from the roots
• Phloem – brings food down from
the leaves

15. Leaf Structures and Functions
• Mesophyll – where
photosynthesis happens
• Palisade mesophyll – closely
packed, lots of chloroplasts
• Spongy mesophyll – loose tissue
with many airspaces

17. • Stomata – pore-like openings in
the underside of the leaf
• Allow CO2 and O2 to diffuse in and
out of the leaf

18. Guard Cells
• Control the opening and closing of
the stomata by responding to
changes in water pressure

20. Transpiration
• The loss of water through its
leaves

22. Gas Exchange
• If stomata were kept open all the time,
water loss due to transpiration would so
great that few plants would be able to take
in enough water to survive.
• Plants keep their stomata open just
enough to allow photosynthesis to take
place but not so much that they lose too
much water.
• The stomata open and close in response
to changes in water pressure in the guard
cells

23. • When pressure is high – stomata
open
• When pressure is low – stomata
close
Q: What time of day do you think
stomata are open and why?
A: Daytime, cause that’s when
photosynthesis happens

24. 24 – 1 Reproduction with
Cones and Flowers

25. Life Cycle of Gymnosperms
• Reproduction in gymnosperms
takes place in cones
• Male cones produce – pollen
grains
• Female cones produce – ovules

26. Structure of Flowers
• Flowers are reproductive organs
that are composed of 4 kinds of
specialized leaves

28. Sepals
• Enclose the
bud before it
opens, leaf-
like

29. Petals
• Brightly colored, attract insects to
flower

30. Stamen
• Male reproductive
structure of flower, Anther
made of 2 parts
• Filament – long,
thin, stalk that
supports the anther
• Anther – makes Filament
pollen grains
Anther + Filament = Stamen

32. Pistil
• Female reproductive structure,
made of 3 parts

33. Stigma
• where pollen
grains land,
sticky

34. Style
• Connects stigma to ovary
Style

35. Ovary
• swollen base of
the pistil where
ovules are formed
Ovary

36. Pollination
• Most gymnosperms and some
angiosperms are wind pollinated,
whereas most angiosperms are
pollinated by animals
• Insect pollination is beneficial to
insects and other animals because it
provides them with food
• Plants also benefit because this
method of pollination is more efficient

37. Q: What kind of symbiotic
relationship is this?
A: Mutualism

38. 25 – 1 Hormones and Plant Growth
• In plants, the division, maturation,
and development of cells are
controlled by a group of chemicals
called hormones

39. Hormones
• A substance that is produced in
one part of the organism and
affects another part of the same
organism

40. Target Cell
• The portion of an
organism affected
by a particular
hormone

41. Auxins
• Discovered by Charles Darwin
and his son
• They were trying to explain
phototropism

42. Phototropism
• The tendency for plants to grow
toward light

44. • Auxins are produced in the apical
meristem and are transported
downward into the rest of the
plant
• They stimulate cell elongation

46. Gravitropism
• The response of a plant to gravity

47. Auxin Like Weed Killers
• High concentrations of auxins can
inhibit growth, so scientists have
produced many auxin like
compounds to be used as
herbicide
• Ex.) Agent Orange

49. Cytokins
• Plant hormones that stimulate cell
division, the growth of lateral buds
and cause dormant seeds to
sprout
• Cytokins often produce effects
opposite to those of auxins

50. Gibberellins
• Promote growth, particularly in
stems and fruits

51. Ethylene
• Stimulate fruits to ripen

52. 25 – 2 Plant Responses

53. tropisms
• The response of plants to external
stimuli
• Ex.) gravitropism and
photoperiodism

54. Thigmotropism
• Growth in response to touch

55. Rapid Responses
• Some plant responses do not
involve growth, they are so rapid it
would be a mistake to call them
tropisms
• Ex.) sensitive plant, venus fly trap

56. Sensitive Plant

57. Venus Fly trap

58. Photoperiodism
• The way a plant responds to periods
of light and darkness
• Short day plants – flower when days
are short
• Long day plants – flower when days
are long
• Photoperiodism in plants is
responsible for the timing of seasonal
activities of plants

59. Dormancy
• The period during which an
organism’s growth and activity
decrease or stop
• As cold weather approaches
deciduous plants turn off
photosynthetic pathways, transport
materials from leaves to roots, and
seal leaves from the rest of the plant