Chamaegigas intrepidus is a rare aquatic plant from Namibia, with a remarkable ability to recover after drought.
About this species
This member of the Linderniaceae family is the only species in its genus. It was first discovered in 1909 by Kurt Dinter, one of the early botanists active in Namibia. As a result of its small stature yet gigantic lifestyle (as an aquatic plant managing to thrive in a desert), it was aptly named Chamaegigas intrepidus, for which the literal translation is ‘intrepid dwarf giant’. It is known as a ‘resurrection plant’ due to its adaptations to multiple environmental stresses.
Geography & Distribution
Chamaegigas intrepidus is restricted to Namibia. It occurs exclusively in small, shallow (not deeper than about 15 cm) ephemeral pools on top of large rock plates, in the central west of Namibia.
Chamaegigas intrepidus flowers (Image: H. Kolberg, NBRI)
The compressed rhizomes (underground stems) are embedded in a thin layer (on average 1 cm thick) of coarse sand, debris from algae and aquatic invertebrates, animal dung and leaf litter, which accumulates at the base of pools. The rhizomes are about 1mm in diameter in their dried state. The plants form fairly solid mats through intertwined, fine adventitious roots.
Chamaegigas intrepidus produces two types of leaves. Those at the base are submerged, forked, awl-shaped and about 1-2 cm long. There are also two pairs of leaves floating on a delicate petiole at the surface of the water, which are oval, unequal, 5-7 mm long, and purple below.
One or two purple-speckled, white or pale pink, two-lipped flowers are produced in the rosette of floating leaves. The tiny (about 0.5 mm long), brown, elongate seeds are wrinkled with a conspicuous pale funicle (stalk attaching the seed to the ovary wall).
Chamaegigas intrepidus is a true resurrection plant that has occupied and amazed many researchers. Several anatomical and biochemical adaptations have been demonstrated which enable the plant to survive in its harsh environment. Plants dry in the sun from 100% relative water content (RWC) (fully turgid) to 8% RWC in a mere 3.75 hours, and air-dry plants take only 1.5 hours to become fully turgid after immersion in water. More than 50% of basal leaves survive after being maintained at 0% relative humidity (RH) for 4.5 months and 100% of both basal and immature floating leaves survive at 5% RH. Mature floating leaves do not survive desiccation as well as basal leaves, which is a feature unique to resurrection plants.
During the course of a wet season, rock pools can become dry and then be re-filled 15-20 times. Resurrection plants halt their development during dry periods and simply resume growth once the pools re-fill. Floating leaves can grow to the surface of the water within 2-4 days after the pools receive water. Flowering has been reported to occur only four days after continuous hydration. Seeds germinate and produce their first true basal leaves within nine days.
Chamaegigas intrepidus also copes with daily fluctuations of temperature and pH, with the latter values in the afternoons being almost double those in the mornings. During the dry season (which can extend up to 11 months of the year), rhizomes can be exposed to temperatures of up to 50°C and, even when rock pools are filled, water temperatures of up to 40°C have been reported, with night temperatures down to 6°C.
Threats & Conservation
Chamaegigas intrepidus in its natural environment, Namibia (Image: H. Kolberg, NBRI)
The very shallow sediment of the pools in which Chamaegigas intrepidus lives gets eroded rapidly when the pools are overflowing during periods of heavy rainfall. Several adaptations assist the plant to cope with this. The extreme shortage of nitrogen in rock pools is compensated for by the ability of the plant to utilise dissolved organic nitrogen, which it obtains from the amino acids glycine and serine through a urease reaction. Urease is a very stable enzyme and can withstand the high temperatures and light intensities which C. intrepidus is exposed to. The dissolved organic nitrogen is absorbed through a highly effective system that operates optimally under low pH conditions. pH can fluctuate widely (up to 6 units) in rock pools, and a very effective pH regulation mechanism of the cell compartments and high stability of cell membranes at low water potential enables the plant to cope with these fluctuations.
The depositing of urine by animals on the rock surfaces surrounding pools plays an important role in the nutrient balance of plants. On the other hand, animals, especially livestock in search of water, also trample the pools, and it was observed during the dry years before 2006, that in many pools the shallow bottom layer had been completely pulverised, or mats of plants had been turned over and destroyed.
C. intrepidus is known from at least 30 populations, with an extent of occurrence of less than 20,000 km². The maximum area of occupancy is only 100–200 km² though, as the actual pools within this area in which C. intrepidus lives are very small.
Over-utilisation of water in the pools could be a threat during dry years, although populations could recover if wetter years followed. Over-collection is not a problem as the species is not well known and is locally common. As populations are currently observed as stable, a Least Concern status can apply regarding the level of threat for this species.
About 330 species of desiccation-tolerant vascular plants are known, of which nearly 90% occur on inselbergs (isolated rocky hills or mountains). The majority of the species are monocotyledons and ferns. Only a few desiccation-tolerant non monocotyledonous angiosperms are known, making Chamaegigas of particular scientific interest. Further research is underway on the anatomical, biochemical and physiological adaptations which enable these plants to survive such environmental extremes.
Millennium Seed Bank: Seed storage
Kew's Millennium Seed Bank partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
Description of seeds: Average 1,000 seed weight = 0.05 g.
Number of seed collections stored in the Millennium Seed Bank: One.
Namibia rarely receives enough rainfall for Chamaegigas intrepidus to make an appearance, but the local Millennium Seed Bank Partnership team were fortunate to discover large populations producing seeds during the plentiful rains of 2005/2006. This level of rainfall had not been seen for 30 years, and it could be another 30 before this species is found to be producing seed again.
Collecting seed from this small aquatic plant presented quite a challenge. Most seeds were found on plants in pools that had almost dried out. This meant that the seed collectors had to lie on their stomachs next to the pool and pick the 1 x 2 mm capsules from under the four floating leaves with a pair of tweezers without crushing the fragile structure. Since the rocks warm up considerably from about 11 am, this had to take place early in the morning, but this was an opportunity not to be missed to secure the future of this remarkable species.
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