Coordination and Control in Plants Flashcards
what is the pigment called that is found in the leaves of flowering plants? and what is its job?
-phytochrome is the pigment system
-it is involved in the timing of flowering in plants
how is the flowering process initiated? what triggers it?
-when average temps reach a certain level
-most common trigger is the duration of light or day length
what is another term to describe the duration of day light?
-photoperiod
what are the two species/ types of plants that are controlled by light?
-long day plants
-short day plants
when do long day plants flower?
-when day length exceeds a certain minimum length
when do short day plants flower?
-when day lengths are shorter/ dark period is longer
what is the term used to describe how the photochrome pigment responds to light?
-acts as a photoreceptor
what is the two forms that phytochrome can be found?
-P660
-P730
what type of light does P660 absorb and what is its absorption peak?
-red light with a peak of 660nm
what type of light does P730 absorb and what is its absorption peak?
-far red light with a peak of 730nm
what happens if the plant is subjected to red light in-terms of the pigment conversions? what about far red light?
-the P660 is rapidly converted to the P730 form
-if there is far red light P730 is rapidly converted to the P660 form
in darkness which pigment is more stable and what does this result in?
-P730 is much less stable in darkness than P660
-P730 will therefore convert to the P660 form slowly
what type of light does daylight contain more of and what is the effect of this in-terms of the pigments?
-more red than far red light
-meaning P660 is converted to P730 so as day length/ light gets longer the amount of photochrome in the form P730 increases
what is the effect of a longer day length in flowering in LDPs?
-as day length increases the amount of P730 increases too until it reaches a critical level which then initiates flowering
what happens are day length increases in short day plants and why is this?
-the inhibitory effect of high levels of P730 must be removed before flowering can take place
-this is due to P730 being physiologically active
what is the phytochrome response in LDP when there is a short day and a long night?
-P660 converted to P730 rapidly in the day
-the night/ dark is long enough for sufficient P730 to be converted back into P660
-this prevents P730 reaching critical level and so prevents flowering
what is the phytochrome response in LDP when there is a long day and a short night?
-long day means P660 can rapidly convert to P730
-dark period is not long enough for P730 to convert back to P660
-P730 stays at critical level and so the plant flowers
what is the phytochrome response in SDP when there is a short day and a long night?
-P660 converted to P730 in the day
-dark period is long enough for a sufficient level of P730 to be converted back to P660
-this removes inhibitory effect of high amounts of P730
-the plant flowers
what is the phytochrome response in SDP when there is a long day and a short night?
-P660 converted to P730 during the day
-dark period is not long enough for a sufficient level of P730 to be converted back into P660
-high amounts of P730 results in flowering being inhibited
what is done by flower suppliers to ensure that flowers are available during the whole year?
-the photoperiod is manipulated
what are the two ways that the photoperiod can be manipulated?
-using artificial light
-using screens to reduce the light period
what is the effect of the light and the dark period in LDPs being the same length?
-the length of day is not long enough to build up a supply of P730 to initiate flowering
what is the effect of having a longer light period and a shorter dark period in LDPs?
-flowering is initiated as the light period is long enough for sufficient amount of P730 to reach the critical level
-the dark period is not long enough to break down a sufficient amount of the P730
what is the effect of light period being longer than dark period but the light period is interrupted by a short period of darkness?
-the short amount of darkness does not reduce the amount of P730 level enough so that it falls below the critical level and inhibits flowering
-this is because the conversion of P730 to P660 in darkness is a slow process