Question

The phenomenon of photoperiodism was first discovered by ......... in the "Maryland mammoth" variety of _________
A) Garner and Allard, tobacco
B) Went, tobacco
C) Garner and Allard, cocklebur
D) Knott, cocklebur

Answer 1

Hint:Plants provide various responses to their environment differently based on different periods of the day and temperature. Different plants need different periods of daylight for flowering. Some plants are also dependent and influenced by temperature changes for flowering.

Complete answer:
The response of a plant to the duration and period of daylight or the periods of day and night is known as photoperiodism. Based on their response to the periods of light, different plants may be classified as short-day plants, long-day plants, or day-neutral plants.

Now let us find solution from given options:
A) Garner and Allard, tobacco : these two scientists worked with tobacco and told that this plant shows different responses to day and night conditions.
B) Went, tobacco : F.W went as the scientist who told us about Auxin in plants. He shows that auxin may be extracted from the coleoptile of tobacco.
C) Garner and Allard, cocklebur : cocklebur is a plant also called clotbur and is a weedy plant. No scientist till now has used this plant in experiment.
D) Knott, cocklebur : he made important contributions in metallurgical processes and told about the fractures.

Hence the correct answer is option ‘A’ i.e, Garner and Allard, tobacco.

Note:
-Short-day plants are defined as the plants that flower when they are exposed to light for periods less than the critical period, for example-Chrysanthemum.
-Long-day plants are defined as those which flowers only when they are exposed to light for more than the critical period, for example-radish. They are also termed as short-night plants. When there is no marked correlation between the duration of exposure to light and the flowering, the plants are usually termed as day-neutral plants. Example- Tomato.