Aponogeton lakhonensis

Lore & Background

The species was named in 1910 by French botanist Aimée Antoinette Camus, who specialized in orchids and oaks. She published the description in Notulae Systematicae: Herbier du Muséum de Paris: Phanérogramie. The plant has an obovoid or elongated rhizome up to 2 cm long, with submerged leaves having petioles 9–15 cm long and floating leaves with petioles up to 40–60 cm. Its inflorescence is a single spike with two yellow, obovate perianth segments about 2 mm long, six stamens with broadened filaments, and carpels slightly united near the base with 4–6 ovules per carpel. The fruit is ovoid with a short terminal beak, 2–3 mm in size. Distinguishing characteristics include a single-spike inflorescence, persistent yellow tepals up to about 3 mm, no stolons, 4–8 ovules, double testa, widened filaments, and a short lateral beak on the fruit. Leaves are mainly submerged, with submerged leaves 25–6 cm and floating leaves up to 17 by 4 cm.

Reader's Guide

Aponogeton lakhonensis is significant as a species that bridges tropical Asian and Australian Aponogeton lineages. Phylogenetic analysis using nuclear and plastid DNA, along with fossil evidence including pollen from the late Cretaceous and early Cenozoic in Greenland, shows it is in a sibling clade with tropical Australian Aponogeton, with a crown date of 5.2 million years ago. The ultimate ancestor of the genus likely lived in the mid-Eocene in Africa or Madagascar. The species is native from Southeast Asia to China and Assam, with an outlier population in Sulawesi. It occurs in paddy fields, ponds, and slow-moving streams up to 800 m elevation. The IUCN rates it as Least Concern, but its habitats are continually diminishing in area, extent, and quality. In Thailand, the whole plant is eaten in salads; in Cambodia, the leaves are served raw with fish sauce. Vernacular names include pak kuap (near Lampang, Thailand), sbay mu:ng (Khmer, meaning 'mosquito net'), and shui weng (Standard Chinese).

Did You Know?

• It is more closely related to tropical Australian Aponogeton species than to other Southeast Asian species.
• In Thailand the whole plant is eaten in salads, while Cambodians prefer the leaves alone with fish sauce.
• Fossil pollen from Greenland suggests an early Cretaceous origin for the genus Aponogeton.