Question

Both a short day plant and a long day plant can produce flowers simultaneously in a given place. Explain.

Answer 1

Hint: The photoperiod affects the flowering period. The flowering can be induced in both the types of plants simultaneously, if they are provided with an adequate photoperiod that is intermediate to the sunlight limit of both the plants.

Complete answer:The duration of the sunlight required by a plant is known as the photoperiod. Photoperiodism is defined as the effect of the duration of light or the photoperiod on the flowering of the plants. It was first observed by Garner and Allard in the tobacco plant in 1920.
The critical photoperiod is defined as that particular period or duration of light, above or below which the flowering is affected. The plants are divided into three groups based on Photoperiodism –
1. Short day plants (SDP)
2. Long day plants (LDP)
3. Day-neutral plants (DNP)
Short Day plants – These are the plants in which the flowering occurs at or below the critical photoperiod. They are also known as the Long night plants as continuous dark periods are more important than light. Example – Tobacco, Xanthium, Paddy, etc.
Long Day plants – These are the plants in which the flowering occurs at or above the critical photoperiod. They are also known as Short night plants. Example – Oat, Wheat, Sunflower, etc.
Now let us suppose that the critical photoperiod of a short day plant is \[x\] hours and that of a long day plant is \[y\] hours. Flowering will occur in a short day plant when it will receive sunlight equal to or less than\[x\] hours. On the other hand, flowering will occur in a long day plant when it will receive sunlight equal to or greater than\[y\] hours. Hence, for both the plants to flower together they must be exposed to the intermediate range of both the critical photoperiods, i.e., from \[x\] to \[y\] hours. This is known as adequate photoperiod.

Note: Both short-day plants and long-day plants can be made to produce flowers simultaneously in a given place with the help of grafting. One branch from the long day plant can be taken and then grafted with one branch taken from the short-day plant. Then the light is provided according to the need of only one plant, i.e., the long-day plant.