Floral studies of palmarosa [Cymbopogon martinii (Roxb.) W. Watson] and chemical insights during inflorescence development

Abstract

Palmarosa [Cymbopogon martinii (Roxb.) W. Watson] is an economically crucial aromatic grass species commercially cultivated for its essential oil. The essential oil has high demand in cosmetics, tobacco products, and perfumery industries. The present study investigates the inflorescence development of palmarosa into ten distinct stages. Light microscopy and morphological observations led to identifying these stages. The pollen is monoporate and spherical in shape (22–32 μm) that is available from the first inflorescence development stage. The stigma becomes receptive at stage - 5. The inflorescence development stage - 6 indicates the highest pollen availability as well as viability. The florets are small lacking sepal and petals, suggesting an anemophilous mechanism of pollination. The open-pollination conditions are best suitable for a good seed set than self-pollinated conditions. The floral biology of palmarosa suggested cross-pollination breeding behavior. Scanning electron microscopy of leaves reveals the presence of essential oil glands (120–145 μm) responsible for its essential oil's rose-like aroma. The analysis of essential oil through gas chromatography-mass spectrometry revealed considerable variations of metabolites in the leaves, inflorescence, and whole plant (excluding roots). Multivariate clustering of oil data showed that the amount of geraniol increases towards maturity. In contrast, the amount of neryl acetate was observed highest at immature stages, and it decreases towards mature inflorescence stages.