What is a critical photoperiod? On the basis of this, plants are categorized in how many types?

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Hint: Plants react differently according to various times of day and temperatures to their climate. Photoperiod is described as day length. For flowering, various plants need various periods of daylight. Some plants also rely on changes in flora temperature.

Complete answer: Plants need to bloom on a certain day. This relatively long flowering day and night is called a photoperiod. Essential photoperiod is the length of the day and night above and below where a plant does not bloom. The following groups are classified into: Depending on the length of photoperiod plants:
a) Short Day Plants (SDP):
Short-day plants typically need less than 12 hours of light, i.e., 8 to 10 hours and continuous darkness for subsequent flora of approximately 14 to 16 hours. Most flowering plants in the winter are in this group. For example, sugarcane, rice and potato, Xanthium and Dahlia.
b) Long Day Plants (LDP):
For subsequent flowering, long day plants need a light cycle of 14-16 hours. This long night cycle prevents flowering entirely. The distinctive characteristic of these plants is that However the night's inhibitive effects and the plants thrive in long nights disturbed by light, even briefly. Sometimes these plants are also called short plants at night. For instance. Spinach, barley, oat, Henbane.
c) Day Neutral Plants (DNP):
All photoperiods of these plants flower and may grow throughout the year. Tomato, cotton, sunflower and cucumber are examples.

Note: Short-day plants are those plants, for example, chrysanthemum, that flower when exposed to light for periods that are not critical. Since it takes less daylight than the critical time, it is also known as long-night plants. Only when exposed to the sun, for example, for longer-days plants are flowering, for longer than the essential duration. Often known as short-night-plants, the plants are called day-neutral plants because there is no clear connection between the time of exposure to light and flora.