Potamogeton gayi is a delicate narrow-leaved pondweed species quite widely spread in the south of South America outside the tropics (Southern Brazil, Argentine). There it grows submersed in stagnant and flowing waterbodies.
Potamogeton gayi has long been known in the aquarium hobby as it is a robust fast grower, however, more recently its dispersion in cultivation and in trade has decreased.
Like in most other Potamogeton species, the thin rhizomes of P. gayi grow creeping and branch out in the substrate. From them, vertical stems grow out at regular distances.
These stems may grow up to a length of about a metre. The lineal leaves grow in two alternate lines on the stem, don't have a stalk and reach a length of 4 to 12 cm and a width of 2 to 5 mm. They are quite soft, translucent, and, depending on the light, their colour can be from green to orange brown. Their midrib is clearly visible. There is also a very thin longitudinal nerve in the middle between midrib and leaf margin. It is connected to the midrib by short vertical nerves.
To be continued...
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