Stern's Introductory to Plant Biology Chapter 11

Growth

irreversible increase in mass due to the division and enlargement of cell

Determinate growth

they grow rapidly at first, then for a while they show little, if any, increase in volume, and eventually, they stop growing completely

Indeterminate growth

they continue to be active in growing for several to many years

Differentiation

the cells develop different forms adapted to specific functions, such as conduction, support, or secretion of special substances

Development

the coordination of growth and differentiation of a single cell into multicellular tissues and organs

Genes

the basic units of heredity, control the synthesis and development of enzymes

Enzymes

proteins that catalyze every metabolic step within cells

Internal environment

nutrients, vitamins, hormones

External environment

water, minerals, gases, light, temperature

Nutrients

substances that furnish the elements and energy for the organic molecules that are building blocks by which an organism develops

Vitamins

play an important role in reactions catalyzed by enzymes; required in relatively small amounts for the normal growth and development of all organism

Coenzymes

organic molecules of varied structure that participate in catalyzed reactions, mostly by functioning as an electron acceptor or donor

Vitamin A in animals

carotene pigments found in chloroplasts act as precursors

Hormones

produced mostly in actively growing regions of plants, are organic substances that differ from enzymes in structure

Growth regulators

emphasize the commercial importance of hormones

Plant hormones

regulate plant development

Signal transduction

include changes in the complement of enzymes produced in a tissue or changes in transport across membranes

Auxins, gibberellins, cytokinins, abscisic acid, ethylene

major known types of plant hormones

Coleoptiles

tubular, closed sheaths protecting the emerging shoots of germinating seeds of the Grass Family - Poaceae

Agar

a substance obtained from marine algae; flat portions of a gelatinlike growth medium

Auxins

promote cell enlargement and stem growth, cell division in the cambium, initiation of roots, and differentiation of cell types

Gas chromatography

hormone concentrations are more determined by vaporizing a sample and moving it through a tube of liquid or powdered material

Indoleacetic acid (IAA)

the only active auxin

Phenylacetic acid (PAA)

more abundant but less active than IAA

4-chloroindoleacetic acid (4-chloroIAA)

found in germinating seeds of legumes

Indolebutyric acid (IBA)

occurs in the leaves of corn and various dicots

Herbicides

plant killers

Gibberellins

not only dramatically increase stem growth, but also are involved in nearly all of the same regulatory processes in plant development as auxins

Gibberellins

Gibberella fujikuroi

Gibberellins

moves through xylem and phloem and, unlike that of auxin, the movement is not polar

Acetyl coenzyme A

functions as a precursor in the synthesis of GA

Gibberellins

now used to increase seed production in conifers and to increase the rate of malting in breweries by enhancing starch digestion

Cytokinins

stimulants to cell division; prolong the life of vegetables in storage; play a role in many of the growth phenomena also brought about by auxins and gibberellins

Abscisic acid (ABA)

growth-inhibiting hormone; movement throughout plants is nonpolar

Dormins

substances that are produced in dormant buds that block the effect of auxins

Ethylene

produced by gas lamps in the laboratory, had produced the abnormal growth; produced from the amino acid methionine

Ethylene

its commercial uses is to ripen harvested green fruits, such as bananas, mangoes, and honeydew melons, and to cause citrus fruits to color up before marketing

Thigmomorphogenesis

responses under control of genes that are activated by touch

Calmodulin

play a vital role in several plant growth responses, constitutes up to 2% of a plasma membrane and is activated when it binds to calcium

Climacteric

accompanying major increase in respiration

Oligosaccharins

released from cell walls by enzymes, influence cell differentiation, reproduction, and growth in plants and therefore must be considered hormones

Brassinosteroids

have a gibberellin-like effect on plant stem elongation, known from legumes and a few other plants

Yams

source of DHEA - a hormone whose production by humans tends to decrease with age- also the source of batasins

Batasins

promote dormancy in bulbils, which are produced from axillary buds in lilies and few other plants

Apical dominance

suppression of the growth of the lateral buds (also called axillary buds), each of which can form a branch with its own terminal bud

Senescence

the breakdown of cell components and membranes that eventually leads to the death of the cell

Nutations

referred to as spiraling movements

Nodding movements

facilitates the progress of the growing plant tip through the soil

Twinning movement

occur when cells in the stems of climbing plants, such as morning glory, elongate to differing extents, causing visible spiraling in growth

Contractile roots

bulbs of a number of dicots and monocots that pull them deeper into the gorund

Nastic movements

alternate in bending down and then up as the cells in the upper and lower parts of the leaf alternate in enlarging faster than those in the opposite parts

Nastic movements

may involve differential growth or turgor changes in special cells

Epinasty

the permanent downward bending of an organ, often the petiole of a leaf, in response to either an unequal flow of auxin through the petiole or to ethylene

Nastic movements

include sleep movements and contact movements in the changes in turgor pressure

Tropism

growth of a plant toward or away from a stimulus

Initial perception phase

the organ receives a greater stimulus on one side

Transduction

occurs, during which one or more hormones become unevenly distributed across the organ

Asymmetric growth

occurs as a result of greater cell elongation on one side

Positive phototropism

growth movement toward light

Negative phototropism

similar bending away from light

Gravitropism

growth responses to the stimulus of gravity

Clinostat

uses a motor and a wheel to rotate a potted plant slowly about a horizontal axis

Statoliths

gravity sensors

Thigmotropism

a plant or plant part response to contact with a solid object

Hydrotropisms

roots grow upward for considerable distances in response to water leaks

True tropisms

responses to water and several other stimuli

Chemotropism

chemicals

Thermotropism

temperature

Traumotropism

wounding

Electrotropism

electricity

Skototropism

darkness

Aerotropism

oxygen

Geomagnetotropism

greater concentrations of roots tend to occur on the north and south sides of wheat seedlings, and it has been suggested that magnetic forces may be involved

Chemotropism

germinating pollen grains produce a long tube that follows a diffusion gradient of a chemical released within a flower

Thermotropic

grow horizontally when cold temperatures prevail and return to erect growth when temperatures become warmer

Turgor movements

result from changes in internal water pressure and are often, but not always, initiated by contact with objects outside of the plant

Pulvini

special swellings located at the bases of leaves

Circadian rhythms

the folding and unfolding usually takes place in regular daily cycles, with folding most frequently taking place at dusk and unfolding occurring in the morning

Dinoflagellates

species of certain warmer marine-water algae glow in the dark through bioluminescence

Bioluminescence

a process by which chemical energy is converted to light energy

Solar tracking

Leaves often twist on their petioles in response to illumination and become perpendicularly oriented to light source.

Phototorsion

twisting of petioles that facilitates heliotropic movements

Taxis

a type of movement that involves either the entire plant or its reproductive cells, occur in several groups of plants and fungi but nit among flowering plants

Flagella

whiplike appendages

Cilia

short, whiplike appendages