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Plant story - collecting the seed of intrepid little giant

Conservationists from Kew's Millennium Seed Bank have collected the seed of intrepid little giant, a truly remarkable plant.

Flowers of Chamaegigas intrepidus (Photo: H. Kolberg)

Introducing intrepid little giant

During the good rains in Namibia in the 2005/2006 season, the local Millennium Seed Bank team succeeded in collecting seed of the remarkable and rare aquatic plant intrepid little giant (Chamaegigas intrepidus). This member of the Scrophulariaceae (Snapdragon) family is the only species in its genus and endemic to Namibia. During most years in Namibia, rains are not adequate for this plant to make its appearance and we were extremely lucky to firstly find a sufficiently large population and secondly at the right moment for seed collection. With the past rains being the first average or above average falls in as many as 30 years for most of Namibia, we may not see this species seeding again in a while.

The species was first discovered in 1909 by Kurt Dinter, one of the early botanists active in Namibia, and, because of its small stature yet gigantic lifestyle, aptly named Chamaegigas intrepidus, which literally translates to "intrepid dwarf giant". 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. At the base of the pools a thin layer (on average 1 cm thick) of coarse sand, debris from algae and aquatic invertebrates, animal dung and leaf litter, accumulates. The compressed rhizomes, which are about 1 mm in diameter in their dried state, are embedded in this layer and plants form fairly solid mats through intertwined, fine adventitious roots. The plant has to cope not only with drying and refilling of pools, but also diurnal fluctuations of temperature and pH with the latter values being almost double that in the afternoons to those in the mornings. During the dry season (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.

The plants produce two types of leaves: at the base submerged, forked, awl-shaped, about 1-2 cm long, and floating on a delicate petiole at the surface of the water two pairs of opposite, oval, unequal, 5-7 mm long, which are purple below. One or two purple speckled, white or pale pink, bilabiate flowers are produced in the rosette of floating leaves. The tiny (about 0.5 mm long), brown, elongate seeds are rugose with a conspicuous pale funicle.

A remarkable plant

Chamaegigas intrepidus is a true resurrection plant that has occupied and amazed many researchers. Several anatomical and biochemical adaptations have been shown which enable the plant to survive in its harsh environment. Plants dry in the sun from 100% relative water content (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 survived after being equilibrated at 0% RH for 4.5 months and 100% of both basal and immature floating leaves survived at 5% RH. Mature floating leaves do not survive desiccation as well as basal leaves - a unique feature for resurrection plants.

During the course of a wet season, rock pools can become dry and re-filled 15-20 times. 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 pools receive water. Flowering has been reported to occur only 4 days after continuous hydration. Seeds germinate and produce their first true basal leaves within 9 days.

The very shallow sediment of pools gets leached rapidly when overflowing during heavier rainfall periods. Several adaptations assist the plant to cope with this. 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, especially livestock, in search for water, also trample the pools, and it was observed during the dry years before 2006, that in many pools the shallow bottom layer was completely pulverised or mats of plants turned over and destroyed.

The challenge of collecting

Collecting seed of this small plant presents quite a challenge. Most seed were found on plants in pools that had already almost dried out. It meant lying on your stomach next to the pool and picking the ca. 1x2 mm large 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 mornings. But this was an opportunity we just could not miss - even though I was strictly speaking on holiday!

Story by Herta Kolberg, NBRI, Namibia | More plant stories

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We have successfully banked 10% of the world's wild plant species and we have set our sights on saving 25% by 2020.

Without plants there could be no life on earth, and yet every day another four plant species face extinction. Too often when we hear these kind of statistics there is little that we can do as individuals, but thanks to Kew's Millennium Seed Bank partnership and the Adopt a Seed, Save a Species campaign there is something that you can do to ensure the survival of a plant species.

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