Plants in the Indian subcontinent have an inbuilt clock that makes them flower and bear seeds when the monsoons are about to hit, says a recent paper by city scientists.
Prof Uma Shaanker and Prof K N Ganeshaiah of University of Agricultural Sciences (UAS), Bangalore, and Dr N A Aravind of Ashoka Trust for Research in Ecolgy and the Environment in the city are the authors of the paper in Biology Letters, published by the Royal Society.
Uma Shaanker says, “Our study has demonstrated the role of the two monsoons in shaping the evolution of fruiting time in plants in India. While it has been known earlier, that plants may be selected to ripen their fruits and seeds to coincide with the arrival of the wet season, there had been no means to evaluate this experimentally. The fact that India has two distinct monsoons that occur at different time of the year, gave us an excellent natural experimental set-up, to evaluate the above.”
“In our study we show that species of plants that occur during South West monsoon path, give fruits in the month of April ahead of the wet season beginning in June and for plants of the same species that occur during North East monsoon path, they fruit in the month of August, ahead of the wet season beginning in October,” he adds.
Giving an example Uma Shaanker said, “A comparative analogy is the arrival of passengers on a train platform. For a train departing at 10 am, we expect passengers to arrive before 10 am (say 9 am) while for the same passengers, if they were to have their train departing at 3 pm, you would expect them to arrive before 3 pm (say 2 pm).
So, what could happen if the monsoons came before their time or did not come at all? He replies, “It is very important to disperse fruits before the arrival of the wet season, else the rain would wet the dispersal structures and hence impair dispersal. Think of silk cotton trees and what would happen to the seeds bearing the silk when they are wet.”
He gives another example, “Plants that have shaped their fruiting time in time with the arrival of the wet season have made several
“evolutionary” adaptations. In the common jack fruit tree, for example, seeds have a viability period of only two weeks. Thus if the rain does not come fall within this period, these seeds will die. Any rain later is of no use.”
Dr K V Ravi Shanker, Principal Scientist at Indian Institute of Horticultural Research, says, “The above study is very interesting and helps us know more about how plant behaviour may change according to changes in climate.”
Let us say, we get mango plant materials from Haryana in north India and grow them in Bangalore. Monsoon in Haryana, comes in July, a month later than in Bangalore. According to the above findings, the plant will now flower and be ready for seed dispersal a little later than local mango trees.