Flowering - Development of plant

One of the major changes that occur during the life cycle of a plant is the transition from vegetative stage to the flowering stage. In this transition the vegetative meristems change into flowering meristems which form sepals, petals, carpels and anthers instead of branches and leaves. It is a major morphogenetic change. In some plants this change occurs once in life-time and after flowering, fruit and seed set, the plant dies. Whereas, in others the flowers are produced every year, as in trees. Now the question arises, is it due to an internal annual rhythm in the plants or a requirement for particular environmental condition? In this section we will tell you what controls flowering and how this transition occurs.

One of the major factors that affects flowering, as we know today is related to the effects of the environment and in particular to the duration of light/dark 24 hour cycle or temperature. However, it took a number of years for scientists to realise this fact. We will describe two experimental observations which suggested that the length of the day determines the behaviour of plants with respect to flowering. The seeds of soya bean (Glycine max) were planted at different times in the month of May, June, July and August. Even though planted at different times, all of them flowered in the month of September. The first planted seeds took 125 days to flower whereas the last set flowered in only 58 days. These observations show that at a particular time of the year the day length was suitable for plants to flower. The second observation was made on a mutant of tobacco called Maryland mammoth, because of the large size of its leaves. In fields it does not flower in winter, however, in glass houses when light duration was provided like that of summer, it was possible to induce flowering even in winter in these plants.