Plant Science Exam 3

What is an autotroph?

A self-feeder, uses CO2 as main source of carbon

What is photosynthesis?

The process of converting light energy to chemical energy in the form of reduced carbon compounds

What is the equation for photosynthesis?

6CO2 + 6H2O + light (protons) ——→ C6H12O6 + 6O2

Light Dependent Reaction

Light reaction, creates energy (ATP)

In a light dependent reaction, chlorophyll absorbs solar energy which…

excites electrons in the reaction center (electron transport chain)

In a light dependent reaction, chlorophyll absorbs solar energy, H2O gives…

H+ and O2

What is the third step in a light reaction?

The final electron acceptor, NADPH

What is the fourth step in a light dependent reaction?

H+ gradient, get ATP

What is the second process in photosynthesis?

Calvin Cycle (Light independent reaction)

What is produced from the calvin cycle?

Sugars (glucose)

In photosynthesis, reduced carbon compounds are shuffled around to…

generate the compound required for a specific purpose

Phosphorylated compounds are often involved in…

metabolism because phophorylated versions of the sugars are more reactive than the non-phosphorylated forms.

What are some factors affecting the rate of photosynthesis?

Light quality (wavelength)

Light intensity

CO2 concentration

Temperature

Water availability

Plant development and source sink relationships

Plant photosynthetic mechanism

How can light quality (wavelength) affect the rate of photosynthesis?

• different pigments (chlorophyll a, b, and carotenoids)

• absorption mostly from red and blue portions of the spectrum

• artificial light

How can light intensity affect the rate of photosynthesis?

Affects plant growth by influencing rate of photosynthetic activity.

How does CO2 concentration affect the rate of photosynthesis?

Increasing CO2 concentration increases rate of photosynthesis

How does temperature affect rate of photosynthesis?

The general rule is that if light is not limiting, photosynthetic rate will double for each 10 degrees C or (18 degrees F) increase in temp for many plant species up to a point

• at very high temps, stomates close to conserve water, so a reduced photosynthetic rate

How does water availability affect the rate of photosynthesis?

Drought leads to closing of stomates; drop in photosynthesis

Water is needed in light reaction of photosynthesis

How does plant development and source-sink relationships affect photosynthesis?

Growth of the plant affects rate of photosynthesis, both in single leaves and in the total leaf canopy

What does source refer to?

A mature leaf- carbs synthesized is in excess of what leaf needs; excess transported to other parts of plant (sinks)

What does sink refer to?

A juvenile leaf- needs carbs for growth

Explain the C3 photosynthetic mechanism

this is about 90% of plant species; sufficient rainfall; moderate light inteity and temp

• rice, wheat, potatoes

CO2 that enters leaf is used to generate 3-carbon phosphoglycerate (PGA)

Explain the C4 photosynthetic mechanism

These plants needs warmer and drier conditions

• corn, sorghum, sugarcane

CO2 attached to a 3-carbon organic acid making a 4-carbon organic acid

Explain the CAM photosynthetic mechanism

Crassulacean Acid Metabolism - warmer and drier conditions like a desert

• some orchids, jade, pineapple

Happens at night, stomates can open without too much water loss

What is the equation for respiration?

C6H12O6 + 6O2 + 36ADP + 36PO4^3- ——→ 6CO2 + 6H2O + 36 ATP

What are the three steps of respiration?

Gylcosis, Krebs Cycle, Electron transport

What happens during glycosis?

6C glucose to 3C pyruvate (PA)

• happens in the cytoplasm

What happens during the Krebs cycle (citric acid cycle)?

complete oxidation of PA to CO2

• occurs in the mitochondria

What happens in the electron transport system?

series of cyclic reactions

• occurs in the cristae (inner walls of mitochondria)

What is the light compensation point?

Light intensity at which photosynthesis and respiration rates are equal

What are the inputs of Fermentation?

pyruvate

What are the outputs of fermentation?

ethanol (plants) or lactic acid (animals), CO2, NAD+

Growth and development in plants leads to change in…

the structure and function of cells, tissues, and/or organs

Growth and development =

change

What is growth?

Growth is an irreversible increase in volume (size) or weight

Where does primary growth occur?

The apical meristem

Where does secondary growth occur?

The cambium layers

What is development?

The progress through the life cycle

What is differentiation?

The change in the structure of cells so that these cells can perform particular fuctions

How does the interaction between genes and the environment affect growth and development?

While a plant’s genes may be expressed a certain way, this expression may be influenced by the conditions surrounding the plant.

How does the genetic make-up affect growth and development?

It affects the way it looks and everything that occurs in the plant throughout its life cycle

How does the environment affect growth and development?

It has an impact on almost everything that is going on in that plant

What are factors that affect growth and development?

Genetic make-up

Environment

Interaction between genes and the environment

What are some environmental factors?

Light, temp, water, gases

What are transcription factors?

Special proteins that regulate gene activity;

turns some genes on and other genes off, depending on signals sent to the nucleus

What are signals?

Plant hormones, some inorganic ions, coenzymes, and other metabolites;

also, environmental factors such as light and temp at certain developmental stages

The environmental factor light includes:

Intensity

Quality

Duration

What is the angle of incidence (AOI)?

the angle a beam of sunlight makes with the earth’s surface

What does AOI affect?

Light intensity and

Amount of light entering or absorbed by a leaf

What is light quality defined as?

Relative quantity of light of different wavelengths contained in a beam of light

• most plant process- 380 nm to 800 nm

  • photosynthesis- 440 nm (blue) and 650 nm (red)

What absorbs light of a specific wave length?

Pigment systems in leaves

What is photomorphogenesis?

a combination of processes that controls shape or form of the plant

Most photomorphogenic responses are regulated by the …

Phtochrome pigement system

The phytochrome pigment system absorbs red light and far-red light, but maximum absorption is at

660 nm and 730 nm

just something to think ab

R:FR is important because it affects the amount of red and far red light absorbed by plant, if less is absorbed plants tend to be tall and spindle, more likely to fall over

What is phototrophism?

The movement of plant parts in response to light

What is phototropin?

A blue light photoreceptor responsible for phototropism

What is another name for solar tracking?

Heliotropism

What is solar tracking (heliotropism)?

A type of phototropism - its when leaf or flower angles adjust to maximize or minimize the plant part’s exposure to sunlight.

• soybean closing, sunflowers following

What is photoperiodism?

The photomorphogenic response to variations in day length

What is critical day length?

The duration of light that determines when a photoperiodic plant will show a response (CDL)

What plant process is controlled by photoperiod?

Flowering

What is autumn syndrome?

series of processes in woody plants growing in temperate climates at the end of summer in preparation for winter; includes acquisition of freeze tolerance, bud dormancy, and leaf fall in deciduous trees

What are strategies for survival?

Under unfavorable conditions, such as cold winters or hot, dry summers, many herbaceous perennials form underground tubers: a short-day response starting at the end of summer in potato, yam, dahlia, and tuberous begonia

What is vegetative reproduction?

To take advantage of the growing season, processes relating to vegetative reproduction are often induced by the long days of late spring or early summer

The farther away you are from the equator…

the fewer the number of available growing days to a mature crop

What is the chilling requirement?

Duration required for complete loss of dormancy

What is vernalization?

Any cold temp treatment that induces or promotes flowering

What is stratification?

The practice of exposing imbibed seeds to cool (35-50 F) temps to break dormancy

What are the stages of development?

• Germination and early seedling growth

• vegetative growth and development

• phase change

• reproductive growth and development

• aging and senescence

What practices can you apply to provide the conditions that will encourage proper growth and devlopment of crops?

Fertilization

Light exposure

Temperature

Plant at the right time

Vegetative growth refers to what?

The growth of roots, shoots, and leaves.

Early vigorous vegetative growth is important.

True

What are determinate plants?

Plants that grow vegetatively for a period of time, then shoot elongation stops when flower buds form at the shoot terminals.

What are indeterminate plants?

They grow continuously until senescence or until some environmental influence stops it

What is a phase change?

A transition stage from juvenility to maturity

What is self-induced flowering?

Majority of agricultural plants form flowers when they reach a certain morphological maturity based on how much heat the plant has received.

What is Growing degree days (GDD)?

measure of heat accumulation; this can be used to predict or control the time of flowering

What is the GDD equation

GDD = high temp + low temp / 2 - 50

What are other factors that bring about the formation of flowers?

Photoperiod and low temperature

What is bypass growth?

axillary buds below the aborted floral apex will grow vegetatively until conditions are favorable again

No pollination is necessary in

floral crops

Pollination is required in…

crops where the fruits or seeds are harvested

What is incompatibility?

When the pollen will not germinate on the stigma or the pollen tube will no elongate

Why does double fertilization occur in angiosperms?

There is also the union of the 2 polar nuclei and a sperm nucleus to form the endosperm.

What is parthenocarpy?

When fruit forms without pollination or fertilization- the fruit will not have seeds

What is fruit development?

The coordinated maturation of all tissues and organs involved in the formation of the fruit

Why would there be thinning of fruit?

To remove excessive fruit

What is the climacteric?

A stage of fruit ripening where there is a burst in respiration and the fruit releases high levels of ethylene

What is senescence?

The terminal, irreversible deterioration in living organisms, leading to to death

Where can senescence be observed?

The whole plant or there is organ senescence

What is deheading?

The removal of old flowers that prolongs flowering.

What are plant hormones?

Natural substances produced by the plant that control plant activities

-may be chemically synthesized and have the same effects as the natural hormones

What are plant growth regulators?

Natural and synthetic plant hormones and other chemical not in plants that influence growth and development

What are groups of natural plant hormones?

Auxins

Gibberellins

Cytokinins

Ethylene

Abscisic acid

What is auxin?

A growth hormone

• basipetal- apex to the base

What is cytokinin?

Regulator of cell division

• upward (from roots)

What is gibberellic acid?

regulator of plant height

• downward & upward

What is ethylene?

A ripening hormone

Only hormone that is a gas

• diffuses throughout plant

What is abscisic acid?

A stress hormone