K. C l water . N um ees, R ichtersveld (R S A ). Aizoaceae. Fig. 3: Ions growing in Numees, Richtersveld. 1 Opophytum aquosum, 2 Mesembryanthemum barkle.
Ions pattern of desert succulents from the Succulent Karoo, South Africa - Can we link ecophysiology and phylogeny? Maik Veste
Can we link ions pattern and phylogeny ?
The Succulent Karoo
From the investigations we can conclude that in the Aizoaceae a correlation between the evolution of plant functional types and ecophysiology within the same family obviously exits. Species of the genus Brownanthus (Aizoaceae, subfamily Mesembryanthemoideae) are typical stem succulents with 12 species in the Succulent Karoo and southern Namib. In the Richtersveld B. pseudoschlichtianus, B. aerenosus, B. pubescens and B. marlothii growing on sandy, loessial and highly saline soils at the coast, respectively. A survey of ion characteristics of the four species (Fig. 5) growing on diferent soil types showed a high accumulation of Na and Cl, which is typical also for halophytic species in the Aizoaceae [3] and other plant families. However, the lowest Na and Cl content can be found in B. marlothii growing on saline soils at the coast and B. pubescens. Both are sister species (Fig. 6) [5]. Surprisingly, the highest accumulation of ions were observed in B. aerenosus growing on sand dunes (Fig. 4,5). The storage of water in the leaves is positive correlated with the salt accumulation.
The Succulent Karoo, a winter rainfall desert in north-western South Africa, is a hotspot of biodiversity with a large number of succulent species. The major succulent families are the Aizoaceae (Fig.1,2), Apocynaceae, Aspodelaceae and Crassulaceae. These succulents have developed various integrated and co-adapted morphological and ecophysiological features that maximise their chances of surviving the detrimental conditions in arid habitats. Crassulaceen Acid Metabolisms (CAM) is a common feature in various southern African succulent plant families. Especially in the Aizoaceae the evolution of photosynthetic pathways can be linked to their phylogeny [2]
Brownanthus marlothii (B.marl), coast
B. pubescens (B.pub.), Annisvlakte
B. pseudoschlichtianus (B. ps.) B. pseudoschlichtianus (B. ps.) Fig.1 Mesembryanthemum barkleyii a bi-annual Aizoaceae in the Richtersveld. Plant height is more than 2 m,fresh weight 120 kg and water storage 110 kg.
Halophytes
B. aerenosus (B. aren.) sand dunes
From a comprehensive screening programme it can be shown that the species of the Aizoceae shows the highest sodium Fig. 4: Brownanthus marlothii (B.marl). B. pubescens (B.pub.), B. pseudoschlichtianus (B. ps.), B. chloride accumulations (Fig. 3) [1,3]. The ions accumulation is aerenosus (B. aren.) closely related to the development of leaf and stem succulence. The most interesting feature is that succulents with high salt Conclusions accumulation expend less energy and hence carbon to envelope In summary, like other succulents from the Aizoaceae, one unit water than succulents with low salt content (e.g. in Brownanthus develops a genetic fxed ion pattern, which Aizoaceae, subfamily Mesembryanthemoideae) [1,4]. can be related to their phylogeny [5]. B r o w n a n th u s ( R ic h te r s v e ld )
A
A iz o a c e a e
7000
a n io n s ( m m o l k g - 1 T G )
5000 3000
c a t io n s ( m m o l k g - 1 T G )
B
5000 3000
Fig. 2: Opophytum aquosum (Aizoaceae), annual mesemb with the highest salt accumulation in the Richtersveld.
1000 w a te r c o n te n t (k g k g -1 T G )
Phyllobolus digitatus B. arenosus
1000 .
7000
16
A
3000
1000 .
c a t io n s ( m m o l k g - 1 T G )
5000
C
12 8
Fig. 3: Ions growing in Numees, Richtersveld.
4 0 1
2
3
4
5
6
7
8
9
10 11 12
C l
N a
w a te r
K
1 Opophytum aquosum, 2 Mesembryanthemum barkle pattern and water content in succulentsyii, 3 Mesembryanthemum pellitum, 4 Brownanthus pseudoschlichtianus, 5 Ruschia spec., 6 Stoberia betzii, 7 Cheiridopsis robusta 8 Othonna opima, 9 Tylecodon paniculatus, 10 Ceraria namaquensis, 11 Aloe ramosissima, 12 Aloe personii.
5000
B
increasing NaCl accumulation
B. pseudoschlitianus
3000
B. nucifer 1000 w a te r c o n te n t (k g k g -1 T G )
a n io n s ( m m o l k g - 1 T G )
N u m e e s , R ic h te r s v e ld ( R S A )
10 8
B. marlothii B. pubescens
C
6 4 2 0
B . m a rl . B . p u b . B .p s [ c o a s t] [A n n is v la k t e ]
B . p s . B . a re n . [d u n e ] [d u n e ]
c h lo r id e
N a
s u lf a t e
K
w a te r
M g
Fig. 5: Ions pattern and water content in four Brownanthus species, Richtersveld (see Fig.4).
Fig. 6: Strict consensus tree of combined molecular analysis for Brownanthus.[5]
References [1] [2] [3] [4] [5]
Von Willert DJ, Eller B, Werger MJA, Brinckmann, E, Ihlenfeldt, H-D, 1992. Life strategies of succulents in deserts with special reference to the Namib desert. Cambridge University Press, Cambridge. 340 pp. Veste M, Thiede J, 2004. Diversity, fexibility and phylogeny of photosynthetic types in the succulent fora of southern Africa. In: Breckle S-W et al. (eds.), Ergebnisse weltweiter Forschung, Stuttgart, 361-370 Veste M, 2007. Der Salzhaushalt der Sukkulenten. Avonia 25(2): 43-50. Waisel Y, 2000. Halosucculence: an old enigma with a new interpretation. In: Spatz H-C, Speck T (eds), Proceedings Plant Biomechanics Conference Freiburg, Thieme, Stuttgart, pp. 278-284. Klak, C, Nowell TL, Hedderson TAJ, 2006. Phylogeny and revision of Brownanthus and its close allies Aspazoma and Dactylopsis (Aizoaceae) based on morphology and four DNA regions. Kew Bull.36: 353-400.
