Effect of Environmental Changes on Phenology and Reproductive Biology of Sida cordifolia with Special Reference to the Temperature and Relative Humidity

Abstract

Impact of environmental factors (temperature and relative humidity) on phenology and reproductive biology of a medicinal plant Sida cordifolia L. growing at district Agra was studied. The study revealed that phenological events (leaf fall, leaf renewal, flowering and fruiting) varied considerably with the fluctuations in temperature and relative humidity. Flowering was observed throughout the year with maximum in the months of February-April (11.8 – 38.3ºC) and August-September (24.4- 33.9ºC). Floral biology studies showed that pollen viability, pollen-ovule ratio and fruit-set percentage was greatly reduced with rise or fall in temperature and relative humidity. The maximum pollen fertility (71%), fruit-set (70- 90%) and pollen-ovule ratio (190:1) was recorded in the month of March when temperature was ranging between 15.1-32.6ºC with 22- 76% RH. With the fall in temperature in the month of January (6.8 - 17.9ºC) the pollen fertility was reduced to 52%. At the end of April 32.5- 45.3ºC with 16- 43% RH, the plants under observation exhibited a gradual decline in fruit-set percentage (45- 55%). The anthesis, anther dehiscence and stigma receptivity also varied during the entire flowering period. As the temperature rises, the anthesis takes place earlier and the time of anther dehiscence and stigma receptivity changed accordingly. In this investigation it was found that the changes in temperature and relative humidity during the entire flowering period was associated with the variation in different phenological and reproductive events in the Sida cordifolia plant.