Flower colour changes in Lantana camara

Abstract

Lantana camara flowers undergo colour change subsequent to anthesis. In the colour variant selected for the present study, pink buds, yellow newly-opened flowers and ageing orange, scarlet and magenta flowers are found in the same inflorescence. The flower pigments were chemically analysed and identified as delphinidin monoglucoside and β-carotene. Thrips are regular pollinators of Lantana under Delhi conditions. Pollination was identified as the trigger for rapid anthocyanin synthesis. Even the presence of one pollen grain on the stigma of a yellow flower was sufficient to cause colour change. Injection of a suspension of pollen into flowers opened in vitro caused pigment changes. An extract of Lantana pollen was also able to simulate the effect of pollination, suggesting the involvement of a pollen factor. The post-pollination shift in petal colouration is caused by the masking of carotenoids by differential amounts of anthocyanin. As thrips are attracted to only yellow flowers, chromatic changes play a role in conserving pollinator energy.