Title: Chapter 6 Vegetative and Reproductive Growth and Development
1Chapter 6- Vegetative and Reproductive Growth and
Development
2- 2. Absorb water
- and mineral nutrients
- 3. Conduct water,
- dissolved materials
- and organic materials
3Shoot and Root Systems
- Some roots also serve as a means of vegetative
reproduction. - Shoot growth tends to balance root growth
4Plant Growth
- Plant growth is defined as size increase by
cell division and enlargement, including the
synthesis of new cellular material and
organization of subcellular organelles - Many different measurements
- fresh weight, dry weight, volume, and size
5Determinate VS Indeterminate Growth
- When plants form flowers at the shoot terminals
after a period of vegetative growth, and most
shoot elongation ceases the growth pattern is
determinate. - A determinate plant grows for a specific period
of time (even in the best environment), flowers,
and dies. 1
6- When plant shoots continue to elongate, and
flowers are produced on leaf axils the growth
pattern in indeterminate. - An indeterminate plant could theoretically live
forever, if it had the perfect environment and
was undisturbed. 1
7Annuals, Biennials, and Perennials
- Annuals - herbaceous plants that complete their
lifecycle seed to seed in one growing season. - Biennials -herbaceous plants that complete their
lifecycle seed to seed in two growing seasons-
not necessarily two years. - Most biennials die shortly after flowering.
- Perennials- can be either woody or herbaceous
plants that survive many years.
8Woody Perennial Shoot Growth Patterns
- Single flush/ formation of terminal resting bud-
most common in our area. - Oaks, conifers, most fruit trees
- Multiple flush/ formation of terminal resting bud
after each. - Subtropical species
- Single flush/shoot tip abortion at season end-
- elm, birch, willow, honeylocust also common in
our area. - Sustained flush/ formation of terminal resting
bud at seasons end
9Root Growth Patterns
- Generally root growth in deciduous woody
perennials - greatest in the spring,
- second peak in late summer or early fall.
- However, some species roots may grow nearly any
time of year. - Root growth in deciduous woody perennials
- coincides with high levels of accumulated
carbohydrates.
10Genetic Control of Growth
- Structural genes- genes involved in protein
synthesis - Regulatory or operator genes- involved in turning
genes on and off
11Environmental Factors Affecting Plant Growth
- Light- influences
- 1. Phototropism which is the bending of stems,
leaves and flowers toward light . - Phototropism is thought to be caused by auxin
accumulation on the dark side of stems. - http//koning.ecsu.ctstateu.edu/Plant_Physiology/p
hototropism.html - Stomate opening and closing is another function
partially controlled by light wavelength (color).
12Environmental Factors Affecting Plant Growth
- 2. Photoperiodism - responses triggered by
variation in length of light and dark periods. - Acclimation, flowering, and tuber formation may
all be photoperiodic responses. - http//koning.ecsu.ctstateu.edu/Plant_Physiology/p
hotoperiodism2.html - Acclimation- the physical and physiological plant
processes in plants which prepare them for
winter.
13Temperature
- Growing days or degree days -can be used to
determine when or if a crop will mature in a
given area. - Degree days
- calculated by taking the mean (average)
temperature in a day and subtracting 40 for cool
season crops or 50 for warm season crops
14Temperature
- Example for one day
- high- 80 low- 60 Mean 70 40 30 degree days
for cool season crops - http//www.ent.iastate.edu/ipm/icm/1998/4-6-1998/d
d.html
15Temperature
- Temperate plants -grow in a range of temperatures
from 39-122 degrees Fahrenheit - 1220 F protoplasm is destroyed
- Solarization- the conversion of light energy to
heat , can cause cell destruction
16Temperature
- At the low end of the range chemical reactions
and cellular activity nearly cease - Below freezing membrane disruption by
intracellular ice formation can cause cell death
17Water
- Plants are about 90 water by weight
- Water -a raw material for photosynthesis and
medium for many chemical reactions in plants - Water is used for plant growth cell expansion
- Water- used for plant cooling- transpiration
- What is evapotranspiration?
- http//www.ianr.unl.edu/pubs/irrigation/g992.htmW
HATIS
18Gases
- Gases-
- The most important gases for plant growth are CO2
and O2 - Carbon dioxide-the carbon source used in sugar
and carbohydrate formation - CO2 regulates the opening and closing of stomata-
- CO2 less than 300 ppm opens stomata if other
environmental factors are favorable
19Gases
- Oxygen (O2) is essential for respiration of both
plants and animals - Oxygen is given off as a final product of
photosynthesis
20Pollutant Gases
- Many gases result from the burning of fossil
fuels and manufacturing - Sulfur dioxide can cause acid rain
- Carbon dioxide can be used by plants but it is
also a greenhouse gas
21(No Transcript)
22Pollutant Gases
- Ozone, ethylene and peroxyacetal nitrates (PAN)
can cause plant injury - http//www.aces.edu/department/extcomm/publication
s/anr/anr-913/anr-913.html
23Phase Change
- Plants go through phase changes just as animals
do - Plant appearance can change dramatically as they
age - For example
- A plant may have alternate leaves as a juvenile
and opposite leaves as an adult - A plant may have lobed leaves as a juvenile and
leaves without lobes as an adult
24Phase Change
- Important physiological changes also occur as
plants mature including - The ability to be induced to flower
- Reduction or loss of ability to form adventitious
roots
25Senescence
- Senescence - an irreversible deterioration
leading to cellular breakdown and death. - Flowering and fruit production use up stored
nutrients and increases the rate of senescence - http//www.worc.ac.uk/departs/envman/courses/hort/
teach.hor/BSC/321/scen.html
26Reproduction and Development
- Fruit and seed production can occur only after a
period of maturation in most plants. - Phases following maturation include
27Reproduction and development
Induction
28Induction and Initiation
- Induction -the phase in which chemical changes
that begin the flowering process take place in
the plant in response to certain environmental
conditions. - Initiation - the transformation of the stem apex
from a vegetative axis to a flowering culm.
29Types of Induction
- Photoperiodic induction - induction by changes in
day length - Plants induced to flower by decreasing the light
period are called short day plants. - Plants induced to flower by increasing the light
period are called long day plants. - In some plants flowering is not affected by day
length day neutral plants.
30Photoperiodism
- It is actually the length of the dark period
which is critical. - If night is interrupted by a brief light period
short day plants will not flower even if the
total of the two light periods is less than the
short day requirement. - The leaf is thought to be the receptor for the
light stimulus with the signal being transferred
to the apical meristem.
31Phytochrome
- Phytochrome is the pigment in plants which is the
receptor for the light signal. - Phytochrome has two forms Pr and Pfr
32Phytochrome
- Pfr is the active form created when Pr is
exposed to red light (660 nm) - Pr is the inactive form which is created
instantaneously when Pfr is exposed to far red
light ( 730 nm). - Pr is also created slowly as Pfr breaks down
overnight in the dark.
33Pr
RED LIGHT
Pfr
FAR-RED LIGHT (instantaneous) OR DARKNESS (slow)
34Low Temperature Induction
- Low temperature induction vernalization
- Temperatures for vernalization generally fall in
the 32-50 F - (0-10 C) range.
35Low Temperature Induction
- Amount of time and the temperature required
varies with species. - Many plants including fruit trees require cold
temperatures to overcome a rest period, not
actually to induce flowering.
36Low Temperature Induction
- Bulb plants like tulips, crocuses and hyacinth
require low temperatures to promote flower
development. - http//www.territorial-seed.com/links/techsheets/t
ech_forcing.html - Olives and Kiwis do require cold temperatures for
induction.
37Flower Development
- The number of inductive cycles needed for flower
initiation can vary from one to many depending on
the species.
38Flower Development
- Induction to anthesis (flower opening) times vary
greatly between species also. - Development can be accelerated somewhat by
increasing temperature with many plants.
39Pollination
- Pollination is the transfer of pollen from an
anther to a stigma. - Self-fertile plants can produce fruit and set
seed with their own pollen, self- sterile plants
can not
40Pollination
- Wind and Insects (especially bees) are the most
common pollinating agents.
41Fertilization
- Angiosperms undergo double fertilization.
- One sperm nucleus unites with the egg to form the
zygote. - One sperm nucleus unites with two polar nuclei
and forms the endosperm.
42Double fertilization
- Double fertilization is when the pollen tube
enters the ovule through the micropyle and
ruptures. One sperm nucleus fuses with the egg
forming the diploid zygote. The other sperm
nucleus fuses with the polar nuclei forming the
endosperm nucleus. Most angiosperms have two
polar nuclei so the endosperm is triploid (3n).
The tube nucleus disintegrates. The food in the
cotyledons is derived from the endosperm which,
in turn, received it from the parent sporophyte.
In many angiosperms (e.g., beans), when the seeds
are mature, the endosperm has been totally
consumed and its food transferred to the
cotyledons. In others (some dicotyledons and all
monocotyledons), the endosperm persists in the
mature seed.
43Fruit Set
- Fruit set must not be too heavy or too light if a
crop is to be profitable. - Plant hormones including auxins, gibberillins and
cytokinins can induce fruit set in different
plants. - Temperature at the time of fruit set is also
critical- too low or too high can result in crop
failure.
44Fruit Growth and Development
- Plant hormones including cytokinins,
gibberellins, ethylene and auxins are involved in
different phases of fruit development. - Auxins appear to affect fruit size increase-
strawberries - After the initial period of intense cell
division, increase in fruit size is due mainly to
cell enlargement
45Plant Growth Regulators
- A plant hormone a substance produced in minute
amounts at one site in the plant and translocated
to another site where it alters growth and
development. - Plant growth regulators include plant hormones
(natural and synthetic) and other non-nutrient
chemicals that when applied to plants influence
their growth and development.
46Plant Growth Regulators
- http//www.plant-hormones.bbsrc.ac.uk/education/ke
nf.htm
47Plant Hormones
- Auxins- the first group of plant hormones to be
discovered. - Auxins influence
- cell enlargement or elongation
- apical dominance
- root initiation
- photo- and geotropism
- abscission of plant parts
- flower initiation and development
- fruit set and growth
- cambial activity
- tuber and bulb formation
- seed germination.
48Plant Hormones
- Auxins -synthesized in the in meristems and
developing tissues and transported basipetally
(toward the roots) - Auxins are involved in apical dominance which
is the suppression of growth of lateral buds. - http//koning.ecsu.ctstateu.edu/apical/apical.html
49Plant Hormones
- IAA indoleacetic acid is a naturally occurrring
auxin. - Synthetic auxins
- IBA- indolebutyric acid,
- NAA-napthaleneacetic acid
- 2,4- dichlorophenoxyacetic acid are synthetic
auxins
50Auxins- Commercial Uses
- Adventitious root initiation- IBA and NAA are
used as dips to promote rooting of cuttings. - http//www.hortus.com/drydip.htm
- Weed control- 2,4-D is an effective and
inexpensive selective broadleaf weed killer - http//www.ianr.unl.edu/pubs/pesticides/g802.htmS
YMPT - http//www.24d.org/
- http//ace.ace.orst.edu/info/extoxnet/pips/24-D.ht
m
51Auxins- Commercial Uses
- Inhibition of stem sprouting- NAA at 10,000 ppm
is effective in preventing sprouts at the base of
ornamental trees. - Tissue culture- IAA or 2,4-D are used in tissue
culture media to initiate adventitious roots
52Suckering on a silver maple
53Gibberellins
- Gibberellins are synthesized in the shoot apex,
especially in leaf primordia. - Gibberellins (GA) can stimulate cell division and
elongation as well as enzyme secretion.
54Gibberellins
- GA may also be involved in flower initiation,sex
expression, fruit growth maturation and ripening. - GA stimulates enzymes in the aleurone layer which
hydrolyze stored materials for the embryo to
utilize in germinating seeds - http//www.plant-hormones.bbsrc.ac.uk/education/ke
nf.htm
55Agricultural Uses for GA
- Increasing the fruit size of seedless grapes-
20-40 ppm GA is sprayed on grapes at fruit set
stage to increase berry size. - Stimulating seed germination and seedling growth-
soaking seeds in solutions of 20- 10,000 ppm GA
has been shown to increase seedling emergence and
growth in many plants.
56Agricultural Uses for GA
- Promoting male flowers in cucumbers- GA applied
to leaves stimulates male flower development
needed for pollen for breeders. - Overcoming cold requirement for some plants- for
azalea and cyclamen GA can be substituted for
cold treatments to stimulate flower development.
57Cytokinins
- Roots supply cytokinins to shoots.
- Cytokinins promote cell division.
- Cytokinins are also involved in cell enlargement,
tissue differentiation, dormancy, flowering,
fruiting, and retardation of leaf senescence. - Benzyladenine (BA) is a synthetic cytokinin that
is used to promote shoot growth in tissue
culture.
58Ethylene
- Ethylene is gas which diffuses readily throughout
the plant. - Ethylene is produced in actively growing
meristems, ripening and senescing fruit,
senescing leaves, germinating seeds and certain
plant tissues when they are injured. - Ethephon is chemical that releases ethylene when
it is applied to a plant.
59Ethylene Uses
- Fruit ripening- used on bananas, tomatoes and
honeydew melons. - Flower initiation- used commercially on various
ornamental bromliads. - freephotos4u.com/garden/bromliad.html
- Growth retardant- the product Proxy is used to
slow the growth rate of turfgrass to reduce the
need for mowing.
60Ethylene Uses
- Changing sex expression-
- can dramatically increase the percentage of
female flowers in cucumbers and pumpkins for
better yields.
61Ethylene Uses
- Degreening citrus- ethylene treatment breaks down
the chlorophyll in the rinds to make fruit
attractive for market. - Harvest aid- ethylene can make fruit and nuts
separate more easily from the tree.
62Ethylene for causing fruit drop
63Harmful Effects of Ethylene
- Leaf abscission and flower senescence- Can be
caused by ethylene, keep cut flowers away from
ripe fruit. - Flower bud abortion- if tulips or other bulb
crops are exposed to ethylene from a rotting
bulb, they will probably abort their flower bud
and not bloom. - Accelerated fruit ripening- one bad apple spoils
the barrel
64Abscisic Acid (ABA)
- ABA is involved in fruit and leaf abscission,
onset of dormancy in seeds and early stages of
vegetative and flower bud rest in woody
perennials. - No commercial use for ABA to date.
- http//www.sidwell.edu/sidwell.resources/bio/Virtu
alLB/plant/hormone.html
65Other Inhibitors
- Most commercially used growth inhibitors work by
inhibiting GA slowing cell division and/ or cell
elongation. - Reduced internode length results in more compact
plants. - Growth retardants are used extensively in flower
production and in turfgrass management.
66Commercial Growth Retardants
- Diaminozide- trade names Alar, B-Nine
- -Alar was used to enhance fruit size and
appearance, now outlawed by EPA - -B-Nine still used extensively for bedding
plants and mums. - Chlormequat- trade names CCC, Cycocel
- -Used for height control of geraniums,
Ponsettia, azalea and some bedding plants. - -Also used to prevent lodging in wheat.
67Commercial Growth Retardants
- Ancymidol- trade name A-Rest
- -Used for height control of potted bulbous
plants and mums. - Paclobutrozol- trade names Bozii, Scotts TGR
- -Used for bedding plant production and turfgrass
growth regulation.
68Presentation adapted from
- Hartmann, et al 1988. Plant Science, Second
Edition, Englewood Cliffs, N.J. Prentice- Hall. - Other References
- 1.http//www.gardenwithinsight.com/help100/0000039
3.htm