Floral symmetry is a fundamental morphological feature of flowering plants (angiosperms) and has played a key role in their ecological adaptation and diversification. However, it remains unclear whether a flower’s shape also influences how it manages water, a critical resource for keeping petals fresh and reproductive organs functional.

In a study published in Plant Diversity, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences showed that floral symmetry is not only associated with pollinator specialization, but also with distinct physiological trade-offs in water transport, drought tolerance, and flower longevity. Actinomorphic (radially symmetrical) flowers and zygomorphic (bilaterally symmetrical) flowers follow fundamentally different hydraulic strategies to maintain floral stability and function during anthesis (the flowering period).

The researchers measured 22 floral traits related to floral water transport, drought tolerance, and reproductive characteristics across 21 actinomorphic and 18 zygomorphic woody species in XTBG.

The researchers found that actinomorphic flowers such as lilies and magnolias rely on higher petal vein density to maintain water supply during anthesis, adopting a high-supply strategy. In contrast, zygomorphic flowers such as orchids and peas exhibit a more conservative hydraulic strategy. They show longer floral longevity, greater drought tolerance, and lower vein density, suggesting an emphasis on water conservation and safety rather than high-flow delivery.

Among the 22 floral traits measured, several remained significantly different between the two symmetry types. Zygomorphic flowers showed tighter coordination among hydraulic, structural, and reproductive traits, forming highly integrated functional modules. This strong synergy likely provides greater hydraulic stability under fluctuating environmental conditions. Actinomorphic flowers, by comparison, exhibited weaker trait coupling, reflecting a more flexible but less integrated system.

The study shows that symmetry also influences how flowers balance water and carbon costs , an increasingly important consideration as climate change intensifies drought and heat stress.

“Floral symmetry is not just a morphological novelty, it is closely linked to physiological function. Because flowers are hydraulically vulnerable organs, understanding how different symmetry types cope with water limitation can help predict which plant lineages may be more resilient under future climates,” said ZHANG Jiaolin of XTBG.

Actinomorphic (radially symmetrical) flowers and zygomorphic (bilaterally symmetrical) flowers. (Image by XTBG)

Available online: 7 April 2026