EFFECT OF LIGHT AND TEMPERATURE ON PLANT GROWTH AND YIELD
We know all the fruit yielding plants like Aam, Jaam, and Boroi etc. plants are planted at almost every home in Bangladesh. It will be seen if you observe carefully that all the plants does not flowers in the same time. Mango tree flowers in winter and its fruits ripe in summer. But Boroi flowers in autumn and fruit ripe in winter. Let we have another example. Bean is a winter vegetable. Cultivated almost at every home in Bangladesh. Its seeds are sown in rainy season and the plant flowers in winter. At the end of winter it's flowering stops and in the next winter after the year it flowers again.
We know the length of daytime is short (long night period) is winter in Bangladesh and in summer and rainy season length of day is longer (Night time shorter) A short day time is required to product flower in bean plants. So it flowers in winter. As the daytime is longer in summer so bean plants does not bloom in summer. Therefore it is observed that in Bean plants vegetative growth takes place in longer day period and in shorter day period it flowers i.e starts yielding. Thus it is understand that in growth and development of plant (Bean is only one example), there is influence of light.
The influence of length of daytime on flowering of plants is called Photoperiodism. In 1920 Garner and Allard observed the affect ofphotoperiods in Maryland Mammoth a variety of tobacco plant. According to effect of length of day and night (photoperiods) upon the flowering time Garner and Allard classified the flowering plants into three classes:
1. Short day Plant: These plants flowers when day length is short.Dahlia,Tobacco, Chrysanthemum are short day plants. They may also call long-night plants. Two species of jute are short - day plants. In 10 - 12 hours photoperiods plants flower in 30 days. More than 12 121 hours of photoperiods delayed flowering.
2. Long day Plant: These plants give flower, when day-length is longer.Sponge guard (Luffa) Lettuce and Beta palonga (Palong) is long day plants. They may also call short night plants.
3. Day-Neutral Plants: Flowering time of these plants does not depend on theduration of daylight. They flower when necessary vegetative growth is completed. Day-neutral plant can be grown in both winter and summer. They flower in both the seasons. Sunflower is a plant of this type. Aus paddy usually a day-neutral plant.
Leaves receive the stimulation of photoperiods.