Chapter 11: Growth and Development

What is growth in plants an increase of?

Irreversible increase in mass due to division and enlargement of cells

Determinate growth

Plant grows, stops growing and dies in one season

Indeterminate growth

Plant or parts of plant grow and continue to be active for several to many years

How do cells develop in differentiation?

Different forms adapted to specific functions

Development

Coordination of growth and differentiation of a single cell into tissues and organs

What two factors determine when growth and development occur?

Genes and environment

What is the function of nutrients?

To furnish elements and energy for plant growth and maintenance

Where is nutrients obtained from?

Air and soil

Vitamins

Organic molecules that participate in catalyzed reactions

What do vitamins usually function as?

Electron acceptors or donor

Where are vitamins synthesized?

In cell membranes and cytoplasm

What is the amount of vitamins required for normal growth and development?

Small amounts

Hormones

Production dictated by genes

What regions are hormones mostly produced in?

Actively growing regions

How are hormones produced and active in compared to vitamins and enzymes?

In smaller amounts

What does responses from plant growth results form?

Signal transduction pathway

What occurs to the molecule in the signal transduction pathway?

Signaling molecule binds to receptor releasing messenger molecule

How does a product of enzyme in the signal transduction pathway react?

Responds to environment cues and catalyzes reactions

What is the function of the five classes of plant hormones?

Regulating most plant development

How do plant hormones act?

By chemically binding to specific receptors

What type of hormone association initiates the effect of the chemical bind?

Hormone-receptor association

What does the chemical binding of hormones trigger series of?

Biochemical events, including turning genes on and off

Biochemical events

Signal transduction

What are the major types of hormones?

Auxins, gibberellins, cytokinins, abscisic acid, ethylene

What occurred when Fritz Went placed the agar block directly in top of the coleoptile?

It grew straight up

What occurred when Fritz Went placed the agar block off center of the coleoptile?

The tip bent away from the side

What can bioassays be used to measure?

Hormone concentrations

What are today’s hormone concentrations measured by?

Gas chromatography

What is an example of bioassay involving agar blocks and coleoptile shoot tips?

Specific number of coleoptile shoot tips are placed in agar, which are placed on a decapitated plant

How can the concentration of auxin be determined by?

The degree of bending

Where does auxin production mainly occur?

In apical meristems, buds, young leaves and actively growing parts of plants

What type of structure are auxins similar to?

Amino acid, tryptophan

What do plant responses vary according to?

Concentration, location, and other factors

Monocots are less sensitive than:

Dicots

Shoots are less sensitive than:

Roots

The effects of auxin involve triggering the production of:

Other hormones and growth regulators

What does the product of hormone or growth regulators from auxins cause to increase?

Dictyosomes to increase the rates of secretion

What is the effect of an increased secretion rate of dictyosomes from Auxins?

Some phases controlled by respiration and many developmental aspects of growth are influenced

What does the effect of Auxin promote in cells?

Cell enlargement, cell decision in the cambium, and differentiation of cell types

What does the effect of Auxin promote in the stem and roots?

Stem growth and initiation of roots

What does Auxin delay in fruit?

Fruit, leaf abscission, fruit ripening

What does Auxin inhibit?

Lateral branching

What does the movement of auxins from cells require?

Energy expenditure

Where does the movement of auxins originate from?

Cells

How is the movement of auxins described as?

Polar, away from the source

Where does the movement of auxin typically move through?

Parenchyma cells surrounding vascular

What kind of acids do natural occurring growth regulators include?

Indoleacetic acid (IAA), Phenylacetic acid (PAA), 4-chloroindoleacetic acid (4-chloroIAA), Indolebutyric acid (IBA)

What kind of acids do natural occurring growth regulators include?

Naphthalene acetic acid (NAA), 2,4-dichlorophenoxy acetic acid (2,4-D)

What does the use of auxins promote stimulate in plants if concentration is correct?

Root production on almost any plant organ

What is auxin that is sprayed used to promote?

Uniform flowering and fruit set

What is auxin spray used to prevent in plants?

Abscission layers from forming

What type of auxins can kill weeds?

(Some) Synthetic auxins

Gibberellins

A substance that caused “foolish seeding” disease in stems, including rice

When was Gibberellins (GA) first discovered?

In 1962

How does Gibberellins (GA) affect infected stems?

Usually growth twice as long, which weakens stems and later dies

What is the movement of Gibberellins? (GA)

Nonpolar

What type of plants grow faster than the other with an application of GA?

Most monocots and few dicots

What is gibberllins involved in the same regulatory process as?

As auxins

What can gibberellins used to stimulate?

Flowering

What can the use of gibberellins be used to break?

Dormancy of buds and seeds

How is the use of gibberellins able to affect the temperature and what it is necessary for?

Lower the temperature threshold necessary for growth

How is gibberellin used for germination?

To eliminate the cold requirement

How does the use of gibberellins affect the speed of conversion of foliage?

Speeds up conversion of juvenile foliage to adult foliage

What occurs when the use of gibberellins is blocked in plants?

Stunted growth of plants

What does the use of gibberellins promote?

Thicker, stronger flower stalks

Cytokinins

Stimulants to cell division

How is the speed of the transition to mitosis from the G2 phase affected if auxins is present in cytokinins?

Cytokinins speed up the transition

What do the different types of cytokinins vary in?

Molecular structure and origin

What are cytokinins similar in composition to?

Adenine

Where is cytokinins synthesized in?

Root types and germinating seeds

How do cytokinins aid in cells?

Enlargement of cells

How do cytokinins aid in regard to tissues?

Differentiation of tissues

How do cytokinins aid in chloroplasts?

The development of chloroplasts

How do cytokinins aid in leaves?

Delays the aging in leaves

What kind of effect does Ascisic acid (ABA) have on stimulate effects of other hormones?

An Inhibitory effect

Where is Abscisic Acid (ABA) synthesized in?

Plastids from carotenoid pigments

What is the movement of ABA? Polar or non-polar?

Nonpolar

Where is ABA commonly found in?

Fleshy fruits

What does ABA prevents seeds from doing in fleshy fruits?

Prevents seeds from germinating while still on plant

What does ABA help leaves respond to?

Excessive water loss

How does ABA interfere with potassium ions in guard cells and how does it affect the stomata?

Interferes with transport or retention, causing stomata to close

What is ethylene produced by?

Fruits, flowers, seeds, leaves, and roots

What is ethylene produced from?

Produced form amino acid methionine

What does Ethylene fruit production cease in absence of?

Oxygen

What does ethylene cause in leafs?

Leaf abscission

Where are Oligosaccharins released from?

Cells walls by enzymes

What does Oligosaccharin influence in plants?

Cell differentiation, reproduction, and growth

What type of concentrations are effects produced by in Oligosaccharins in comparison to auxins?

At concentrations 100x less than auxins

What do Brassinosteroids bind to?

Receptors on cell surfaces

What do Brassinosteroids affect?

Apical dominance, gravitropism, seed germination

Apical dominance

Suppression of growth of lateral (axillary) buds

What is apical dominance believe to be brought about by?

An auxin-like inhibitor in terminal bud

What type of trees is apical dominance strong in?

Trees with conical shapes

What are examples of trees with conical shapes?

Pines, spruces, firs

What type of trees is apical dominance weak in?

In trees that branch more often

What do trees that branch more often include?

Elms, ashes, willows

What occurs when cytokinins is applied in appropriate concentrations to axillary buds?

Growth, even in presence of terminal bud

What is Senescence a break down of?

Breakdown of cell components and membranes, eventually leading to death of cell

How does Senesence cause leaves of deciduous trees and shrubs to drop?

Through abscission

How are new organs produced in plants during the senescence process?

From recycled nutrients of leaves