Spigelia genuflexa: it buries its own seeds

A new plant, which deposits its seeds directly into the soil, has been discovered in the state of Bahia, on Brazil’s east coast. Its species name was chosen accordingly: Spigelia genuflexa (literally, ‘that which bends its knee’).

Once the fruits have ripened, after flowering, the flower stalk bends so that they reach the ground and are buried a few centimetres beneath the mossy surface of the soil in which it grows! This adaptation makes it a geocarpic plant. The species is annual. The first inflorescences are produced when the plant is only one centimetre tall, i.e. very early in its life cycle. New inflorescences develop a few months later, when the plant has reached its maximum height of between 15 and 25 cm. It is the fruits from the first flowering that sink into the ground; the second set remain a few centimetres above the surface.

A friend of Alex Popovkin, an amateur botanist living in Bahia, found the plant. After contacting several experts in an attempt to identify the plant, Popovkin concluded that it bore no resemblance to anything previously known. He was able to secure the assistance of Lena Struwe, a botanist at Rutgers University in New Jersey, to describe it.

The scientist put forward a hypothesis as to why the plant had developed such an adaptation, based on observations of the plant itself and its habitat. She first noted that it grows only in environments with very specific characteristics, which are found only in very localised areas. For its survival, it is therefore in the plant’s best interests to deposit its seeds right next to itself, where conditions are identical, rather than allowing them to be carried away by the wind or animals.

Furthermore, the new plants that emerge from the seeds are unlikely to be disturbed by the parent plant whilst they are growing, as the parent plant disappears during the dry season.

The few plants that use this method most often grow on steep cliffs. Geocarpy is therefore a way of safeguarding their seeds; without this ability, they would easily be carried away by the wind to environments less favourable to their growth or consumed by seed-eating animals.

Spigelia genuflexa belongs to the Loganiaceae family, which includes, amongst others, gentians.