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55 Cards in this Set

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what are the roles of control systems?
allowes a plan to interact with its environment

a link between cause and effect

allows one part of the pant to control another part
what are hormones and what was the first study ?
these are chemical signals that cordinate the parts of the plant

darwin conducted the first study of plant response to a stimuli with the study of phototropism
what are the characteristics of hormones
controls plant growth and development by affecting division, elongation and differentiation of cells
in what concentration are hormones produced?
in very small concentrations , the signal is then amplified in some way
what actions might hormones act in?
altering gene expression, affecting the activity of existing enzymes and changing the properties of membranes
what does the reaction of hormones depend on?
its relative concentration to other hormones and its hormonal balance
what is an auxin?
any chemical that promotes elongation of young developing stems or coleptiles.
where is the site of auxin synthesis?
apical meristem of shoots- this is one of the most imporant factors
what do auxins affect?
cell elongation in SHOOTS and ROOTS
what effect does the concentration of the auxin have at low and high concentrations?
high=effects shoots

low=effects roots
think low as in roots, think high as in shoots
how do auxins get to the roots
polar transport probably through parenchyma cells (active transport), moves very slowly down the stem (about 10mm/hr),
will auxins still move even if the plant is upside down?
yes,
what is the acid growth hypothesis?
acid breaks down the microfibril in the cell walls
do proton pumps play a rool in the acid growth hypothesis?
yes, the PP in the plasma membrance plays a role in growth response through lowering the PH of the cell wall, then activating enzymes that break cross-links between cellulose microfibrils, losening the fabric of the wall, ---the cell will now take up WATER! yippee!!
what are some other effects of the auxin on the plant?
induces cell division in the vascular cambium

promotes developement of leaf traces

auxin from seeds promotes growth of fruit

one example, 2-4-d
what on earth is cytokinins?
this is a process that stimulates cytokinesis or CELL DIVSION
where is cytokinins produced?
actively growing tissues, e.g. roots, embryos, and fruits
where do cytokinins produced in the roots move?
up the plant in the xylem
what are the effects of cytokinins in the presence of the auxins?
if the explant is cultured without cytokinins: the cells grow large and DO NOT DIVIDE

if the explant and the cytokinins are there alone there is NO EFFECT

if the explant plus the auxin plus the cytokinis are there the cells divide but the cells remain UNDIFFERENTITED (this is a Callus)
what are the effects of cytokinins in the presence of the auxins?
if the explant is cultured without cytokinins: the cells grow large and DO NOT DIVIDE

if the explant and the cytokinins are there alone there is NO EFFECT

if the explant plus the auxin plus the cytokinis are there the cells divide but the cells remain UNDIFFERENTITED (this is a Callus)

if the explant plus low auxin plus high cytokinis =shoot buds that develop on the callus

if you have the explant plus high auxins plus low cytokinins he ROOTS will develop on the callus.
how is apical dominance controled in axillary buds?
auxins supress axillary bud development

cytokinins stimulate axillary bud development

buds further removed from the terminal bud will be controlled by cytokinis from the roots
how are lateral branching in roots an shoots controled?
the auxin controls branching in roots and cytokinins control branching in shoots
how many gibberellins are there and what is it named after?
this is named after the funus of the genus gibberella,

more than 70 different gibberellins, some of these naturally occur in plants
where is the site of production of the gibberellins?
in the ROOTS and YOUNG leaves near shoot apex
what effect do gibberelins have on the plants?
stimulates growth in leaves and stems (stem elongation) with little effect on the roots growth

fruit growth: dual control by auxin and bibberelin

germination: high concentration in embryo promotes germination and growth
what are tropisms?
growth respones that reslt in curvature of whole plant organs toward or away from stimuli....cell elongation causes this movement
what is phototropism?
light causes the redistribution of auxins, causing it to bend in one direction or the other
what is gavitropism? what effect does it have on the roots, shoots,
a response to gravity. that causes a postive response in roots, negative in shoots,
what is a statoliths?
plastids containing dense starch grains , further more it allows plants to tell up from down
what is thigmotropism?
a response to touch, i.e. grape vien tendials
are tropisms slow , permanent movements/?
yes
what is turgor movement?
the movement caused by changes in tugor pressure of specialized cells in response to a stimuli
what is rapid leaf movement? what are Pulvini?
in mimosa plants there is a rapid loss of tugor by cells within the PULVINI, which are specialized motor cells located at the JOINTS of the leafs.
what is action potential? what is an example of this in the plant world?
these resemble the nervous systems in animals, however the action potential in plants is thousands of times slower than that of the animals. actional potential is clearly seen in te venus fly trap as a bug comes in and then the pant closes due to the action potential
what is sleep movement?
daily changes in the turgor pressure that effects the motor cells in pulvini and cause plant to lower or raise their leaves.
what is a circadian rhythms and te biological clock?
a physiological cycle with a freqcuency of 24 hrs.
what does it mean that the clock is endogenous?
internal of the plant
how do u set the biologcal clock?
with enviromental stimuli , e.g. sunlight and photoperiod
what is a free runing period?
plant kept in a constant environment deviate from 24 hrs (21-27 hrs)
where is the location of the biological clock?
in the cells in the leaves
what is photoperiodism?
a response to day (light) length or a response to nigh (dark) length
what is photoperiodism?
a response to day (light) length or a response to nigh (dark) length

e.g. daylight getting longer or shorter
what is a short day plant?
a plant that requires a light period shorter than a critical lenght to flower

if the critical length of light is 13 hrs , the plant will NOT flower until the season of the yr. when the day length is 13 hrs or less
what is a long day plant'?
requires a light period longer than a critical length to flower
whatid a day neutral plant?
a plant that does not respond to to photoperiod
what are phytochromes?
pigments that effect flowering, seed germination and other respones to photoperiod
what is the critical night length?
night length, not day length, actually controls flowering and other responses to photoperiod
what is the evidence for flowering hormone?
leaves detect photoperiod and triggers hormone to induce flowering
what is florigen? the hormone
controls the flowering of a pant in the presence of light
what is phytochrome?
this plays a role in determining the length of darkness in a photoperiod.
true or flalse? phytochrome CAN act as an hourglass to mark time during the night
false , cannot act as an hourglass
what are the three parts to the signal transduction pathways?
reception, transduction, and induction
what is reception?
occurs on the surface of the taget cell. the stimulus might be a hormone.
what is transduction?
it is performed by a second messenger such as Ca++ and calmodulin
what is induction?
the Ca-calmodulin complex that induces certain respones such as the proton pump activation, gene regulation and the K+ efflux from the guard cell.