Welwitschia

Welwitschia is a unique type of plant found in the Namib desert. It belongs to a group called gnetophytes, which includes other genera like Gnetum and Ephedra. Specifically, it is a monotypic genus. This means it is the only living species in its genus, Welwitschia mirabilis. It is also the only member of its family, Welwitschiaceae, and its order, Welwitschiales. This plant is famous for its strange shape and its ability to live for a very long time. Some individual plants may live for as much as 2,000 years.

The plant has a very unusual way of growing. It begins its life as a seedling with two small pink cotyledons. These quickly turn green after germination. Soon, two permanent leaves emerge from a large, woody stem called a crown. These leaves grow continuously throughout the entire life of the plant. They are long and ribbon-shaped with parallel veins. In the beginning, the plant has an apical meristem, which is a growing tip. However, this tip dies early on. The growing activity then moves to the edge of the crown. This allows the two leaves to grow across the entire circumference of the stem. Over time, the leaves can reach several meters in length. The crown itself is disc-shaped and can widen to one meter in diameter.

Welwitschia is dioecious, which means there are separate male and female plants. Both male and female plants produce cones that grow from the crown. These cones can range in color from green to salmon or various shades of brown. The cones produce a sweet nectar to attract insects. Most often, flies visit the nectar and carry oval-shaped pollen to other plants. While the Welwitschia bug is often seen on the leaves, it likely does not help with pollination. Other insects, such as bees and wasps, also occasionally help move pollen. This process ensures the plant can reproduce even in a harsh environment.

History tells us how scientists first discovered this desert wonder. An Austrian botanist named Friedrich Welwitsch documented the plant in Angola in 1859. He was so amazed by its appearance that he feared it might be a figment of his imagination. Welwitsch originally wanted to name the genus Tumboa, after the local name N'tumbo. However, Joseph Dalton Hooker of the Linnean Society of London chose to name it Welwitschia instead. Hooker used descriptions and materials from Welwitsch and the artist Thomas Baines. This name honored the man who first studied it so closely. Today, the plant's scientific classification remains very similar to what Hooker first established.

The biology of Welwitschia is quite complex at a genetic level. Scientists have sequenced about 98% of its genome. This genome is very large, consisting of 6.8 Gb distributed across 21 chromosomes. About 86 million years ago, the species underwent a whole-genome duplication. More recently, environmental stress like drought caused increased retrotransposon activity. This led to extensive genomic reshuffling and a lot of repetitive DNA. To save energy, the plant uses DNA methylation to silence these sequences. This process also reduced the GC-content to about 29.07%. This is one of the lowest values ever recorded in seed plants.

Surviving in the Namib desert requires special adaptations. The plant lives between the 14th and 24th southern parallels in Angola and Namibia. This area is extremely arid. Some parts of the coast receive almost zero rainfall. The plant often relies on groundwater and moisture from fog to stay alive. The seeds are very hardy and can survive extreme temperatures. They can handle heat as high as 50°C and cold as low as -10°C. Interestingly, some indigenous people eat the cones, either raw or baked in ashes. In the Herero language, the plant is called onyanga, meaning "onion of the desert."

While the wild population is currently stable, Welwitschia faces certain risks. It grows in only one specific ecological area, which makes it vulnerable. The plant has low growth and recruitment rates. Fungal infections, such as Aspergillus niger, can cause seeds to rot in the wild. This fungus often attacks the growing cones. Other threats include overgrazing by animals like rhinos, zebras, and domestic livestock. Human activity, such as damage from off-road vehicles, also poses a risk. Because it is a single-environment species, these pressures could impact its future survival.