1. Plant Growth and Reproduction
Chapter 9.3 and 9.4

2. Growth in Plants
Undifferentiated cells in the meristems of plants allow indeterminate growth
Determinate: growth stops when a certain size is reached
Indeterminate: when cells continue to divide indefinitely
Most differentiated cells are totipotent as well; they have the capacity to generate whole plants

3. Meristems
The tissue in most plants containing undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place.
Primary meristems: found at the tip of stems and roots (apical meristems)- elongation
Root apical meristem- control root growth
Shoot apical meristems- control stem growth
Secondary meristems: growth that increases diameter (lateral meristems)

4. Apical Meristem
Shoot Meristem
Root Meristem

5. Role of Mitosis
Cells in meristems undergo division constantly via mitosis and cytokinesis
Shoot meristem
Throws off cells needed for growth of the stem
Produces groups of cells that grow into leaves and flowers
With each division a cell remains in the meristem while others increase in size, differentiates and are pushed from the meristem region
Each apical meristem can give rise to different tissues
Protoderm= epidermis
Procambium= vascular tissue

6. Plant hormones Plant hormones control growth in the shoot apex
A hormone is a chemical message send from one region that can alter activity in another region
Auxins – a group of hormones that control growth in roots, fruits and leaves
The most abundant auxin is indole-3-acetic acid (IAA)
IAA promotes elongation of cells in stems
At high concentrations it inhibits growth

7. Axillary Buds
Axillary buds are shoots that form at the junction, or node, of the stem and the base of a leaf
As the shoot apical meristem grows and forms leaves, regions of the meristem are left behind at the node
Growth at nodes is inhibited by auxin produced by shoot apical meristem (apical dominance)
Further from a node lower auxin levels
Cytokinins produced in the root promote bud growth
The relative ration of cytokinins and auxins determine if buds will develop

8. Experiment

9. Plant Movement
Plants can adapt to their environment by changing orientation
Tropism
Movement is in a direction either toward or away from a stimulus (e.g. phototropism, gravitropism)
Nastic Movements
Movements that occur in response to environmental stimuli
the direction of the response is not dependent on the direction of the stimulus.

10. Gene Expression
Auxin influences gene expression, which can influence growth rates
Phototropism starts by the protein phototropin absorbing light, causing a conformational change
They then bind to receptors within the cell, which control transcription of genes for glycoproteins (PIN3) that transport auxin cell to cell

11. Intracellular pumps
Auxin efflux pumps can set up concentration gradients of auxin
If phototropins in the tip detect a greater intensity of light on one side of the stem compared to the other, auxin is transported laterally to the shaded side
Higher concentrations on shadier side increase growth there, so the stem curves toward the light

12. Phototropism

13. Gravitropism Also is auxin dependent
The upward growth of shoots and downward growth of roots is due to gravity
If roots are placed on their side, gravity causes organelles called statholiths to accumulate on the lower side of cells
This leads PIN3 transporter protein to move Auxin downward
High auxin levels in this case reduce root cell growth, so the tops elongate and the root bends downward
NOTE: AUXIN ACTIONS ARE OPPOSITE IN ROOTS AND SHOOTS

14. Gravitropism

15. 9.4 REPRODUCTION

16. Angiosperms Angiosperms are flowering plants, They are divided into;
Dicotyledons (dicots):
A flowering plant (angiosperms) that has a seed with two embryonic leaves or cotyledons.
Monocotyledons (monocots)
A flowering plant (angiosperms) that has a seed with one embryonic leaf or cotyledons.

17. Monocots vs. Dicots Monocots Dicots (Eudicots)
Embryo with single cotyledon
Embryo with two cotyledons
Pollen with single furrow or pore
Pollen with three furrows or pores
Flower parts in multiples of three
Flower parts in multiples of four or five
Major leaf veins parallel
Major leaf veins branched
Stem vascular bundles scattered
Stem vascular bundles in a ring
New roots are adventitious (stem)
New roots develop from radicle ( pre-existing roots)

18. Terms
Adventitious root- a root that develops from somewhere other than the root apical meristem
Cotyledon- A cotyledon is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon may become the embryonic first leaves of a seedling.
Radicle – part of root meristem

19. Root Structure

20. Stem Structure

21. Monocot or dicot?

22. Reproductive structures
Male parts:
Stamen
Anther
Filament
Female Parts:
Pistil
Stigma
Style
Ovary
Ovule
Other:
Petal
Sepal

23. Dicotyledonous Flower Parts
FUNCTION
Sepals
Protect the developing flower while in the bud
Petals
Modified leaves; often colourful to attract pollinators
Stamen
The “male” reproductive structure; made of anther and filament
Anther
Produces and releases pollen
Filament
Stalk of stamen that holds up anther
Carpel
The “female” reproductive structure; made of ovary, style, and stigma

24. Pistil
Can refer to a single carpel or a group of fused carpels
Stigma
Sticky top of carpel which pollen lands on
Style
Supports and holds up the style; gives the stigma exposure to pollen
ovary
Base of carpel in which the female sex cells develop; if fertilization occurs, it will turn into a protective fruit
Ovules
Found in the ovary; contain female sex cells, eggs
Pollen
Contain male sex cells (sperm). Pollen grain is one of the granular microspores that occur in pollen and give rise to the male gametophyte of a seed plant

25. Flowering
Flowers are reproductive structures and are produced by the shoot apical meristem
Flowering involves a change in gene expression in the shoot apex
Vegetative Phase: When a seed germinates a young plant is formed that grows roots, stems and leaves
Reproductive Phase: when meristems start to produce flowers instead of leaves

26. Factors affecting Flowering
Temperature- limited effect and varies based on plant
Day length (length of darkness)- greatest effect
Short day plants: flower when darkness lengths increase
Long day plants: flower when there is decreased length of darkness
Light- can inhibit or activate genes controlling flowering
Long day plants; the active form of the pigment phytochrome leads to the transcription of the flowering time gene (FT)
Length of darkness is the trigger NOT length of daylight

27. PLANT TYPE
FLOWERING AND LIGHT
EXAMPLES
LONG-DAY PLANTS
Bloom when days are longest and nights the shortest (midsummer)
- Require Pfr
Radishes, spinach, lettuce
SHORT-DAY PLANTS
Bloom in spring, late summer, and autumn when days are shorter
- Inhibited by Pfr
Poinsettias, chrysanthemums, asters
DAY-NEUTRAL PLANTS
Flower without regard to day length
Roses, dandelions, tomatoes

28. Phytochrome Phytochrome is a photoreceptor and a pigment
It absorbs light
There are 2 forms of phytochrome
Pr – absorbs red light
Pfr – absorbs far-red light/darkness

29. Far-Red Light Wavelengths between 700-800nm
At the far end of the visible light spectrum
(Between red light and infrared light)

30. During the day, when there is light, red light (wavelength of 660nm) is present
Pr absorbs red light and is rapidly converted into Pfr
At the end of the day, after many hours of light, plants will have most of their phytochrome in the form of Pfr

31. During the night, when there isn’t light (therefore no red light), Pfr is slowly converted back into Pr
By morning, most of the phytochrome will be Pr again
If there is even a flash of light interrupting the darkness during the night, it will disrupt the process of Pfr turning into Pr

32. Pr Pfr _____________________________________________________________ Pfr Pr

33. Long-day plants, require Pfr to flower
Long day = short night!
At the end of a short night, there will still be lots of Pfr remaining.
The remaining Pfr at the end of a short night stimulates the plant to flower.

34. In short-day plants, the Pfr acts as an inhibitor for flowering.
So after a short night, the remaining Pfr will prevent the plant from flowering.
If it was a long night, all the phytochrome will be in the form of Pr (there will be no Pfr) so flowering CAN occur.

35. Pollination
The process in which pollen (which contains the male sex cells –sperm) is placed on the female stigma.
Can occur via a variety of vectors
Wind
water
Insects
Birds
Bats

36. Angiosperms and their pollinators have coevolved (supported by fossil evidence)
The flowers colours, patterns, odours, shapes and even the time of day it blooms are designed to attract a specific pollinator
Often, the flower provides the gift of food to the pollinator in exchange for the pollinator unintentionally transporting pollen to the stigma

37. Mutualism
Mutualism- a close relationship between two species where both species benefit
Most flowering plants use a mutualistic relationship with pollinators in sexual reproduction
Pollinators gain food (nectar), while the plants pollen is distributed to another plant.

38. Types of pollination
Self Pollination – when pollen from the anther of a plant falls on its own stigma
A form of inbreeding – thus less genetic variation
Cross Pollination – pollen lands on the stigma of a different plant.
Increases variation and offspring with different fitness

39. Fertilization
When the male and female sex cells unite to form a diploid zygote.
The female sex cells are in the ovules. The sperm from the pollen that has attached itself to the stigma must make its way to the ovules in the ovary.

40. Pollen attaches to stigma and begins to grow a pollen tube through the style
Within the growing pollen tube is the nucleus that will produce the sperm.
The pollen tube completes growing by entering an opening at the bottom of the ovary
The sperm moves from the tube to combine with the egg of ovule to form a zygote.

41. Pollen tube

42. The Seed and Seed Dispersal
Once the zygote is formed, it develops with the surrounding tissue into the seed
As the seed is developing, the ovary around the ovule matures into a fruit
Seed dispersal can be aided by water, wind, animals
Reduces competition between offspring and parent and helps spread the species

44. SEED
Is the means by which an embryo can be dispersed into to distant locations.
It is a protective structure for the embryo

46. Seed Part
Function
testa
Tough, protective outer coat
cotyledons
Seed leaves that function as nutrient storage structures
microphyle
Scar of the opening where the pollen tube entered the ovule
Embryo root and embryo shoot
Become the new plant when germination occurs

47. Pre-Germination Once seeds are formed, a maturation process follows.
The seed dehydrates until the water content of the seeds is about % of its weight.
At this point, the seed goes into a dormant period where there is low metabolism and no growth or development.
Duration is variable for different types of seed
It is an adaptation to environmental conditions

48. Germination Conditions
If conditions become favourable, the seed will be germinated.
GERMINATION – is the development of the seed into a functional plant.
There are several conditions that must be fulfilled for a seed to germinate.

49. Germination Conditions
Water- rehydrates dried seeds, swells the seeds/cracks the seed allowing hydrolytic enzymes to be activated
Oxygen- needed to perform cellular respiration for growth
Temperature- important for enzyme activity for growth. Ensures plants don’t germinate in winter (seedlings are fragile).

50. Metabolic Processes during Germination of a Starchy Seed
Seed absorbs water (which leads to many metabolic changes)
Gibberellin is released after the uptake of water
Gibberellin – plant growth hormone

51. Gibberellin triggers the release of the enzyme amylase
Amylase causes the hydrolysis of the starch into maltose
Maltose is hydrolyzed into glucose which can be used for cellular respiration or converted into cellulose to build cell walls for new cells

52. Stored proteins and lipids will also be hydrolyzed to make proteins/enzymes and phospholipids and energy metabolism.
Germination uses the food stored in cotyledons to grown until it reaches light when it starts to photosynthesize