Photoperiodism | SDP | LDP | Phytochrome | Class 12 In Urdu & Hindi

ALI ACADEMY BIOLOGY LECTURES
ALI ACADEMY BIOLOGY LECTURES
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About This Video ........................

In This Video Lecture You Will Learn Basic Concept Of Photoperiodism
Apart from photosynthesis and phototropic responses, another very important way in
Photoperiod afects lowering, when shoot meristems start producing loral buds
instead of leaves and lateral buds.
which light exerts its inluence on living organisms is through variations in day length
Later on, further studies indicated that it is really the length of the dark period which
Efect of photoperiodism was irst studied in 1920 by Garner and Allard. They studied
naturally lowers under same conditions, in autumn, but lowering could be induced
days, but the long night is interrupted by a short light period, lowering is prevented.
called photoperiod. In plants, photoperiod and temperature afect lowering, fruit and
seed production, bud and seed dormancy, leaf fall and germination.
and day-neutral plants lower without being inluenced by photoperiod.
to classify lowering plants into long-day plants, which require long days for lowering
by conditions artiicially to short days exposing. With further studies they were able
is critical. Thus short-day plants are really long-night plants. If they are grown in short
that tobacco plant lowers only after exposure to a series of short days. Tobacco plant
Long-day plants will lower in short days if the long night period is interrupted
Further experimentation also revealed that quantity of light is also inluenced by the quality of
accumulates in the day and diminishes at night, short day plants coud lower only if the night were
provides the plants with a means of detecting whether it is in a light or dark environment. The rate
during the night it contains more phytochromes in the form of P 660. The presence of either form
to P 660 conversion occurs in the dark. Thus during the day a plant has P 730 phytochromes while
long enough, during which a great amount of P730 would not be completely inactivated, so that
inhibit lowering in short day plants but promote lowering in long day plants. Because P 730
of P 660 to P 730. Other factors, like presence or absence of light and length of dark, or light
This response to light intensity and quality led to the discovery of blue pigment that is red light
wave length of 660 nm and is converted to active P 730, P 730 absorbs far red light at 730 nm and
long day plants, under conditions during which lowering normally takes place. This observation led
revealed that red light was efective in preventing lowering and far-red light reversed the efect of
light. Cocklebur, a short day plant, will not lower if its long night is interrupted but experiments
is converted to P 660. In nature, the P 660 to P 730 conversion takes place in day light and P 730
sensitive protein, the phytochromes.
period also play an important role in lowering. Phytochromes seems to be responsible for the
at which P 730 is converted to P 660 provides the plant with a “clock” for measuring the duration
of darkness.
According to this hhypothesis, p 730, converted from P 660 by the absorption of red light, would
that the time measuring phenomenon of lowering is not totally controlled by the interconversion
enough P 730 would remain at the end of night to promote lowering. But now it is generally agreed
It has been found that red light inhibits lowering the short day plants but promotes lowering in
to hypothesize that the P730-P660 interconversion might be the lant time - regulator for lowering.

About This Channel.....................

I make these videos cause I love to draw and connect the complexity of science and medicine into art. I'm not saying. I'm 100% correct in all my videos, but I do try to obtain the information from credible sources.
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_ students in class 11, 12 or appearing for competitive medical exams ( NMDCAT ) will find it very beneficial
_ The videos are categories under various heading to make the students life simplified

Visit My Other Channel Playlist .....................

NMDCAT PART 1: New 1st Year Biology

NMDCAT PART 2: New 2nd Year Biology

Class 11th Lectures: New 1st Year Biology

Class 12th Lectures: New 2nd Year Biology

Class 10th Lectures:
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