Chemical plasticity and volatile organic compound diversity in Anthemis cotula L.: variations across growth cycles, plant organs, and elevations

This study investigates the volatile organic compound (VOC) diversity of Anthemis cotula L., an European native species that has adapted to grow as both summer and winter annual in the Kashmir Himalaya, and explores whether differences in VOC profiles between these growth forms could shed light on their potential role in the plant’s invasiveness and prolific spread in the region. This study identifies 167 VOCs, with winter annuals exhibiting significantly greater VOC diversity (143) compared to summer annuals (88), as also confirmed by significantly higher Shannon and Simpson diversity indices in winter annuals (p < 0.0001). Winter annuals produced 79 unique VOCs, while summer annuals had 24, with plants of both growth cycles sharing 64 compounds. Terpenes, particularly sesquiterpenes, and monoterpenes, dominated in both growth cycles, but winter annuals showed higher diversity, including a higher abundance of esters (34 vs. 21). VOC profiles also varied by plant part: flowers were rich in esters, while roots and leaves had more terpenes. Elevation had a moderate impact on VOC composition, with the greatest variability observed at higher elevations (2350 masl). Functional Hill diversity was significantly higher in winter annuals (p < 0.0001), suggesting a broader biosynthetic diversity. Redundancy analysis revealed that VOC distribution in plant parts was influenced by environmental variables, with altitude showing a stronger correlation in roots. Molecular network analysis showed VOC segregation in distinct clusters, highlighting the biosynthetic pathway complexity and intricate relationships between chemical compounds of different organs in both growth forms. These findings provide critical insights into the potential role of VOC diversity in the invasiveness of A. cotula, particularly its winter annuals in the Kashmir Himalayan region with potential implications for its management.