November 1, 2019

The Strangest Plant on Earth


 

“He wrote that he was so astonished that he knelt on the hot sand in bewilderment, thinking that his fantasies had taken flight.”
Chris Bornman, describing the reaction of Friedrich Welwitsch upon seeing Welwitschia mirabilis for the first time.

A fine candidate for the most world’s most biologically unique plant, Welwitschia mirabilis is the sole member of the family Welwitschiaceae. This strange cone-bearing plant was first brought to the attention of science by the plant explorer for whom it was named.


Friedrich Welwitsch was an Austrian, trained in medicine and botany, who disappointed his parents by not developing a law career. Instead, after briefly working as a physician, he pursued his interests in plants, working for important botanical gardens in Portugal and England. His African explorations resulted in the discovery of several new species. Welwitsch died in 1872 but left a fine collection of many thousands of dried herbarium specimens. Three hundred and twenty nine species of plants and animals have been named in his honor.

Namib Desert Fog. Image by Juliane Ziedler
Welwitschia is related to other cone-bearing plants, such as cycads and the relic family of trees and vines, the Gnetaceae. From evidence in the fossil record, the ancestors of Welwitschia diverged from other conifers at least 114 million years ago. The ancestral Welwitchias' forest habitat dried and vanished; the modern species seems like a fanciful creation from the imagination of Dr. Seuss. Welwitschia mirabilis is a woody, two-leaved dwarf “tree” that ekes out it existence in parts of the Namib Desert of Angola and Namibia in areas that can receive no rain at all for several consecutive years. As in western South America, the plant communities of the coastal Namib Desert have evolved to rely upon the nightly fogs that are generated by cold ocean currents. Welwitschia’s metabolism requires some foggy humidity to function, but the species ultimately survives by tapping into deeper soil moisture that is recharged by infrequent rainfall. 
Male and female plants bear cones  on short branches; the winged seeds need a bit of surface soil moisture to germinate. Consequently, the reproductive success rate is low. Outlandish claims are often made concerning Welwtschia’s longevity. More accurately, by measuring the growth rates of their leaves, it’s estimated that individual plants can live 500 to 1000 years.

Welwitschia seedling. Image by H. Maurer
 Welwitchia Seedlings grow two tough strap-like leaves that elongate throughout the plants’ lives. Desert winds twist and shred the long, tough leaves. After many decades the tangled, unkempt mature plants resemble dirty piles of rubbish.

Welwitschia near Swakopmund, Namibia. Image By Joh Henschel
  
Image by Thomas Schoch

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