Welwitschia Mirabilis Hook. Fil. — A Cam Plant? Ecophysiological Investigations in the Central Namib Desert

1983 ◽  
pp. 185-191 ◽  
Author(s):  
D. J. von Willert ◽  
E. Brinckmann ◽  
R. Baasch ◽  
B. M. Eller
Keyword(s):  
Namib Desert ◽  
Cam Plant ◽  
Welwitschia Mirabilis

scholarly journals A baseline assessment of the photosynthetic potential of Welwitschia mirabilis using the JIP-test for monitoring and conservation purposes

Bothalia ◽  
2021 ◽  
Vol 51 (1) ◽  
Author(s):  
J.M. Berner ◽  
H. Cloete ◽  
T. Shuuya
Keyword(s):  
Land Use ◽  
Health Status ◽  
Baseline Assessment ◽  
Namib Desert ◽  
Photosynthetic Potential ◽  
Long Term Monitoring ◽  
Welwitschia Mirabilis ◽  
Harsh Climate ◽  
Term Monitoring

Background: Welwitschia mirabilis is highly specialised to survive the harsh climate of the Namib Desert. Changes in land use, such as the expansion of mining activities, may endanger their survival.Objectives: The purpose of this study was to understand the photosynthetic potential of W. mirabilis plants to provide a baseline for future long-term monitoring, and for future comparison to determine plant health status after the onset of mining operations.Methods: The study was conducted in a population of W. mirabilis on the Welwitschia Plains. Chlorophyll a fluorescence data were used to measure plant photochemical potential and analysed using the JIP-test.Results: Significant differences in the photosynthetic potential was observed for W. mirabilis plants located in different catchments. The partial parameters of the PIABS values were also significantly lower, which indicated that all aspects of photosynthesis were influenced.Conclusion: PIABS values can serve as a baseline for future long-term monitoring studies to detect any changes in the health status of W. mirabilis that might result from land use change.

scholarly journals Plant Ecology of the Namib Desert

Afrika Focus ◽  
1991 ◽  
Vol 7 (4) ◽  
pp. 355-400 ◽  
Author(s):  
Patrick van Damme
Keyword(s):  
Sand Dune ◽  
Plant Ecology ◽  
Desert Plant ◽  
Namib Desert ◽  
Endemic Plant ◽  
Photosynthetic System ◽  
Fog Water ◽  
River Bed ◽  
Welwitschia Mirabilis ◽  
Endemic Plant Species

The Namib desert is reportedly the oldest desert in the world. It consists of a number of very distinct ecosystems, six of which are dealt with in this text. Among them are the sand dune, the dry river bed and the domed inselbergs vegetation. The importance of fog water absorption for the Namib flora is discussed. Two important and noteworthy endemic plant species, i.e. Welwitschia mirabilis and Acanthosicyos horrida are treated extensively, because of their great interest for plant physiology and ethnobotany, resp. Special attention is given to the imponance of the CAM photosynthetic system for Namib desert plant survival. Where possible the ethnobotanic importance of the species is discussed.

CO2 gas exchange and transpiration of Welwitschia mirabilis Hook. fil. in the central Namib desert

Oecologia ◽  
1982 ◽  
Vol 55 (1) ◽  
pp. 21-29 ◽  
Author(s):  
D. J. von Willert ◽  
B. M. Eller ◽  
E. Brinckmann ◽  
R. Baasch
Keyword(s):  
Gas Exchange ◽  
Namib Desert ◽  
Co2 Gas ◽  
Co2 Gas Exchange ◽  
Welwitschia Mirabilis

scholarly journals Welwitschia: Phylogeography of a living fossil, diversified within a desert refuge

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Norbert Jürgens ◽  
Imke Oncken ◽  
Jens Oldeland ◽  
Felicitas Gunter ◽  
Barbara Rudolph
Keyword(s):  
Genetic Relationships ◽  
Intraspecific Diversity ◽  
Gene Pools ◽  
Environmental Niche ◽  
Namib Desert ◽  
Isolated Populations ◽  
Living Fossil ◽  
Rock Types ◽  
Bioclimatic Variables ◽  
Welwitschia Mirabilis

AbstractWelwitschia mirabilis is one of the most extraordinary plant species on earth. With a fossil record of 112 My and phylogenetically isolated within the order Gnetales, the monotypic genus Welwitschia has survived only in the northern Namib Desert in Angola and Namibia. Despite its iconic role, the biogeography, ecological niche, and evolutionary history of the species remain poorly understood. Here we present the first comprehensive map of the strongly disjunct species range, and we explore the genetic relationships among all range fragments based on six SSR markers. We also assess the variation of the environmental niche and habitat preference. Our results confirm genetic divergence, which is consistent with the hypothetical existence of two subspecies within Welwitschia. We identify an efficient geographical barrier separating two gene pools at 18.7°S in northern Namibia. We also identify further diversification within each of the two subspecies, with several different gene pools in ten isolated range fragments. Given the presence of well-isolated populations with unique gene pools and the association with different bioclimatic variables, rock types, and habitats within arid river catchments, we can hypothesize that the present intraspecific diversity may have evolved at least in part within the present refuge of the northern Namib Desert.

scholarly journals Very high extinction risk for Welwitschia mirabilis in the northern Namib Desert

2020 ◽  
Author(s):  
Pierluigi Bombi ◽  
Daniele Salvi ◽  
Titus Shuuya ◽  
Leonardo Vignoli ◽  
Theo Wassenaar
Keyword(s):  
Climate Change ◽  
Extinction Risk ◽  
Namib Desert ◽  
Isolated Populations ◽  
Research Attention ◽  
Area Of Occupancy ◽  
Welwitschia Mirabilis ◽  
The Impact ◽  
Very High ◽  
Iucn Criteria

AbstractOne of the most recognisable icon of the Namib Desert is the endemic gymnosperm Welwitschia mirabilis. Recent studies indicated that climate change may seriously affect populations in the northern Namibia subrange (Kunene region) but their extinction risk has not yet been assessed. In this study, we apply IUCN criteria to define the extinction risk of welwitschia populations in northern Namibia and assign them to a red list category. We collected field data in the field to estimate relevant parameters for this assessment. We observed 1330 plants clustered in 12 small and isolated stands. The extent of occurrence has a surface of 214.2 km2 (i.e. < 5000 km2) and the area of occupancy a surface of 56.0 km2 (i.e. < 500 km2). The quality of habitat is expected to face a reduction of 69.47 % (i.e. > 50 %) as a consequence of climate change predicted in the area. These data indicate a very high extinction risk for welwitschia in northern Kunene and classify these populations as endangered (EN) according to IUCN criteria. Similar assessments for other subranges are prevented by the lack of relevant data, an issue that deserves further research attention. Our results advocate the necessity of a management plan for the species, including measures for mitigating the impact of climate change on isolated populations across its fragmented range.

Welwitschia mirabilis: CAM or not CAM — what is the answer?

2005 ◽  
Vol 32 (5) ◽  
pp. 389 ◽  
Author(s):  
Dieter J. von Willert ◽  
Nicole Armbrüster ◽  
Tobias Drees ◽  
Maik Zaborowski
Keyword(s):  
Citric Acid ◽  
Gas Exchange ◽  
Extensive Study ◽  
Co2 Uptake ◽  
Natural Ecosystems ◽  
Cam Plants ◽  
North West ◽  
The North ◽  
Cam Plant ◽  
Welwitschia Mirabilis

After more than 20 years of extensive study we found clear evidence that Welwitschia mirabilis Hook.f. is able to take up CO2 at night in both of its natural ecosystems, the Namib desert and the Mopane savannah, and hence should be classified a crassulacean acid metabolism (CAM) plant. At six different sites, 85 W. mirabilis plants were marked and the growth rate of their leaves and leaf ribbons were measured over a period of 2.5 years. The slowest and the fastest growing plant of these 85 plants were from the Mopane savannah and from the north-west of the Brandberg massif, respectively. These were selected for the gas-exchange measurements of this study. Within the course of a year nocturnal CO2 uptake was found only in December and January when the nights were shortest and plants were flowering. CO2 uptake during the night was not pronounced and never accounted for more than 4% of the total CO2 uptake over 24 h. Maximum rates of nocturnal CO2 uptake never exceeded 0.1 µmol m–2 s–1 for the slowest and 0.2 µmol m–2 s–1 for the fastest growing plant. Neither water availability in the soil nor night temperature was found to determine nocturnal CO2 uptake in terms known for CAM plants. Regardless of the growing site all leaves of W. mirabilis contained high amounts of malic and citric acid. Small increases of acids over night as calculated from the gas exchange measurements are masked by the extremely uneven distribution of these acids in the leaves, making the feature of an overnight malic or citric acid accumulation an unsuited test for CAM in W. mirabilis. An increase in 13C discrimination with increasing distance from the coast was confirmed. Photorespiration was extremely high and followed air temperature around the leaf. Although the debate whether or not W. mirabilis is a CAM plant can be closed, no answer could be given why W. mirabilis makes so little use of CAM.

scholarly journals Ecophysiological studies on Welwitschia mirabilis in the Namib desert

1983 ◽  
Vol 2 (3) ◽  
pp. 209-223 ◽  
Author(s):  
B.M. Eller ◽  
D.J. von Willert ◽  
E. Brinckmann ◽  
R. Baasch
Keyword(s):  
Namib Desert ◽  
Welwitschia Mirabilis
Sign in / Sign up

Export Citation Format

Share Document