How plants are classification based on photoperiodism?
Answers
On the basis of Photoperiodism responses the plants are divided in to different types by Garner & Allard. The short-day flowering plants, long-day flowering plants and day-neutral plants.
Classification of Plants Based on Photoperiodism
Short-Day Flowering Plants
The plants that flower when the day length is less than a certain critical length termed as short-day plants (SDPs). These plants require a specific short duration of light period for speeding up flowering. The day length in excess of critical point will keep the short-day flowering plant vegetative:
The critical day length varies from species to species. The common examples of short-day plants are Maryland mammoth (Nicotiana tabacum), cocklebur (Xanthium pennsylvanicum), soyabean (Glycine max), cosmos (Cosmos bipinnata), etc.
Long-day Flowering Plant
The plants that flower when a critical day length is exceeded are called long-day plants (LDPs). These plants require exposure to longer durations of light periods before the flowering is initiated. The critical day length differs from species to species in LDPs as in short-day plants. Some examples of long-day plants are:
spinach (Spinacea oleracea), sugar beet (Beta vulgaris), black henbane (Hyoscymus niger), lettuce (Lactuca sativa). These plants remain vegetative if grown under short-day conditions.
Day-Neutral Flowering Plants
The plants whose flowering is not affected by either short or long durations of light are called day-neutral plants. These plants flower after a period of vegetative growth. Some examples of day-neutral plants are tomato (Lycopersicum esculentum), four-o’ clock (Mirabilis), certain varieties of pea (Pisum sativum), cucumber (Cucumis sativus) and maize (Zea mays).
Since, Garner & Allard’s work, the classification of plants according to photoperiodic responses has been expanded.
Short-Long-Day Flowering Plants
The plants that require exposure to a number of short days followed by long days for initiation of flowering are called short-long-day plants. These plants flowers in late spring or early summer when there is shift from short to long days. The common examples of short-long-day plants are winter rye (Secale cereal cv. Petkus) and candytuft (lberis durandii]
LONG SHORT DAY FLOWERING PLANT
The plants in which flowering is induced after exposure to long-day conditions followed by short duration of light are called long-short-day plants. These plants flower in late summer or early fall, for example bnjophyllum daigremontianum and night-jasmine (Cestrum nocturnum).