Plant Growth and Development
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FÅÇTØRS ÏÑFLÜËÑÇÏÑG THË ÅÇTÏØÑ ØF PGRS
Intrinsic factor: Genomic control.
Extrinsic factors: Light and Temperature.
RØLË ØF LÏGHT ÅÑD TËMPËRÅTÜRË ØÑ
FLØWËRÏÑG
PHØTØPËRÏØDÏSM
It is the response of plants to periods of day/night.
Some plants require light to induce flowering.
Based on light duration, plants are of 3 groups:
Long day plants: They require the exposure to light for a period exceeding
a well-defined critical duration.
Short day plants: They require the exposure to light for a period less than
the critical duration before the flowering is initiated in them.
Day-neutral plants: They have no correlation between exposure to light
duration and induction of flowering.
Flowering in certain plants depends not only on a combination of light
and dark exposures but also their relative durations. This response of
plants to periods of day/night is termed photoperiodism.
While shoot apices modify into flowering apices, they by themselves
cannot perceive photoperiods. The site of perception of light/dark
duration is the leaves.
(NEET 2019)
It has been hypothesised that there is hormone(s) for flowering. When
plants get enough photoperiod, the hormone migrates from leaves to
shoot apices to induce flowering.
Phytochromes are photoreceptors that help to detect light in bacteria
and fungi. Phytochrome is a chromoprotein.
(NEET 2016)
VËRÑÅLÏSÅTÏØÑ
It is the phenomenon in which some plants depend
quantitatively or qualitatively on exposure to low
temperature for flowering.
(AIPMT 2006)
It prevents precocious reproductive development
late in the growing season, and enables the plant
to have sufficient time to reach maturity.
Vernalisation refers specially to the promotion of
flowering by a period of low temperature.