Biology chapter 30 readings 04/07/2014
• Plants hormones may have localized effects or effects on other parts of the plant (or both)
• Plant hormones can move via the vascular system, or from cell to cell, or even via intercellular spaces
In plants a Hormone is a signaling molecule that regulates or helps coordinate some aspect of the plants
growth, metabolism or development.
Plant hormones act in response to two general types of cues:
1) interchemical conditions related to growth and development
2) conditions in the external environment that affect plant growth, such as light or the availability of
there are seven major classes of plant hormones: auxins, gibberellins, cytokinins, ethylene,
brassinosteroids, abscisic acid, and jasmonates. herbicide is any compound that at proper conditions kills plants (some are selective, killing one class
of plants and not others)
polar transport – unidirectional movement of a substance from one end of a cell (or other structure) to
the acidgrowth hypothesis suggests that auxin causes cells to secrete acid (H+) into the cell wall
by stimulating the plasma membrane H+ pumps to move hydrogen ions from the cell interior into the cell
wall; the increased acidity activates proteins called expansins, which penetrate the cell wall and disrupt
bonds between cellulose microfibrils in the wall.
Bolting – rapid formation of a floral shoot in plant species that form rosettes, such as lettuce Senescence – is a closely controlled process of deterioration that leads to the death of plant cells
Abscission – the dropping of flowers, fruits, and leaves in response to environmental signals
Hypersensitive response – a defense that physically cordons off an infection site by surrounding it
with dead cells
Pathogenesisrelated proteins (PR proteins) – some PR proteins are hydrolytic enzymes that
break down components of a pathogen’s cell wall.
Phytoalexins – biochemical of various types that function as antibiotics. When an infectious agent
breaches a plant part, genes encoding Phytoalexins begin to be transcribed in the affect tissue.
Geneforgene recognition – this term refers to a matchup between the products of the dominant
alleles of two types of genes: R gene (for resistance) in a plant and an Avr gene (for avirulence) in a
Systemic acquired resistance – the defensive response to a microbial invasion may spread
throughout a plant, so that the plant’s healthy tissues bec