Chenopodiaceae)

430 S.Afr.I.Bot.. 1992. 58(6): 430 - 439 The ecology and identification of the southern African Salicornieae (Chenopodiaceae) M.O'Caliaghan National Botanical Institute, P.O. Box 471, Stellenbosch, 7599 Republic of South Africa Received 11 February 1992; revised 15 June 1992 The Salicornieae is represented in southern Africa by three genera: Sarcocornia A.J. Scott (nine species), Salicornia L. (four species) and Halosarcia P.G. Wilson (one species). Approximately 500 specimens of this tribe from the four major herbaria in South Africa (STE, BOl, NBG, PRE), as well as living populations, were examined. The peculiar anatomy, morphology, habitat and ecological features are discussed. Keys based on morphological and habitat characters are presented to facilitate identification. Many of the specimens were previously incorrectly identified and a relatively high proportion were hybrids. In suidelike Afrika word die Salicornieae verteenwoordig deur drie genera: Sarcocornia A.J. Scott (nege spesies), Salicornia L. (vier spesies) en Halosarcia P.G. Wilson (een spesie). Ongeveer 500 eksemplare van die vier hoofherbaria in Suid-Afrika (STE, BOl, NBG, PRE), asook lewende populasies, is bestudeer. Die besonderse anatomiese, morfologiese, habitat- en ekologiese eienskappe word bespreek. Sleuteis gebaseer op morfologiese en habitatkenmerke word aangebied. 'n Groot aantal van die eksemplare is voorheen verkeerd ge'identifiseer en 'n relatief hoe proporsie is hibriedes. Keywords: Chenopodiaceae, Sarcocornia, Salicornia, Halosarcia, identification, ecology. Introduction Chev.) was unsatisfactory and further study was required. The taxonomy and identification of the Salicornieae have A number of criticisms might be raised regarding these proved to be difficult since the last century (Moquin 1840). taxonomic developments. For example, the stem anatomy of The South African species were revised by Moss (1948, Halosarcia indica is different to all the other Salicomieae, 1954) to include two genera: Arthrocnemum Moq. (15 whereas the absence of sclereids and the covering of the species) and Salicornia L. (2 species). The taxonomic flowers by the subtending bract place this species close to history and validity of the specific concepts were discussed Sarcocornia natalensis Bunge ex Ung.-Sternb. Furthermore, by Tolken (1967) in his review of the South African species the distinction of Sarcocornia mossambicensis from S. of Arthrocnemum (10 species) and Salicornia (three perennis is based on a difference in hairiness of the seed species). testa and a tapering as opposed to non-tapering inflores Tolken's concept of Arthrocnemum indica (Willd.) Moq. cences. In my experience, these degree differences are not was placed in the genus Halosarcia P.G. Wilson by Wilson easily distinguished. (1980) by virtue of the absence of sclereids in the palisade This study is not an attempt to revise these taxa, rather it tissue and the adaxial position of the stamen, The remaining is an attempt to facilitate their identification. This is to be nine species of Arthrocnemum were placed in the genus achieved through a practical key which highlights the mor Sarcocornia AJ. Scott by Scott (1977) on the basis of phological and ecological features which are useful in membranous or hairy testa and the absence of endosperm in identifying the Southern African Salicomieae. For this the seed. purpose it is assumed that the taxa are acceptable and, Brenan (1988) described Sarcocornia mossambicensis notwithstanding subsequent taxonomic developments, the Brenan whose distribution seems to be restricted to the specimens identified by Tolken (1967) for his study are Mozambique coast. However, this new species is similar to correctly named and can be used as reference. Sarcocornia perennis (Mill.) AJ. Scott and some specimens of S, perennis from the northern Natal coast, might in fact Anatomy, morphology and ecology be S. mossambicensis. I have not seen specimens which Superficially, the Salicornieae appear to have succulent, have been definitively identified as Sarcocornia mossam jointed, leafless stems containing chlorophyll. The flowers bicensis and, as it seems to have a very restricted distrib are small, inconspicuous and sessile, subtended by a bract, ution, I have not included it in the present study. and usually occur in groups of three or more. Inflorescence, Tolken (1967) discussed two forms of Salicornia pachy perianth, stamens and ovaries do not have a high taxonomic stachya Bunge ex Ung.-Sternb. The first has an erect habit value as there is little variation between the species. Stigma with all branches ending in a spike which is 20 - 30 (50) and seed characters are more useful, but these are easily lost mm long. The second has a nearly decumbent habit and or destroyed in specimen preparation. flowers appear first at the end of the main branch. Flowers These plants are usually found in wetland habitats which may appear'later or not at all on the lower branches. The are highly stressful and unpredictable environments. The flowering spikes are 20 - 50 (80) mm long. This second different species show similar adaptations to the environ form was recognized as a distinct species by Brenan (1988), mental stresses, but must remain plastic to survive the varia although he did state that this taxon (Salicornia perrieri A. bility. As a result, the species are similar in appearance and S.Afr.J.Bot., 1992, 58(6) 431 the morphology of each species is highly variable. usually be distinguished as a colourless line in fresh material Furthermore, these species hybridize easily. Tolken (Figure 1). (1967) recorded 24 putative hybrids between 8 species of In some species, the older segments die. These dead seg Sarcocornia. ments may remain attached to the plant or may be lost. In Flowering is often dependent on environmental factors. herbarium material, distinction must be made between dead Each species generally has a four to six month flowering leaves (those that died prior to sampling) and dried leaves. period, usually during summer to autumn. However, the Aerial parts of the plant that do not have succulent leaf flowering period of a particular population may be relatively sheaths are referred to as stems. short, depending on the occurrence and duration of condi The inflorescence, in the form of a spike, consists of tions favourable for flowering. For example, an estuary numerous bracts which are anatomically similar to the mouth might remain closed during most of the flowering leaves, although usually shorter. A cymule, consisting of season resulting in the vegetation being flooded and not usually three or more flowers, is found in the axil of each being able to flower. Only if the floodwaters recede for bract (Figure 1). some reason will the vegetation be induced to flower. Favourable flowering conditions might prevail for a short Methods period only, might occur out of normal flowering season, or Of 507 specimens from four of the major herbaria in South might not occur for a number of years. Africa (BOL, NBG, PRE, STE), 230 had been identified by Salicornia, Sarcocornia and Halosarcia (to a lesser Tolken for his revision (TOiken 1%7). The morphology, extent) are cosmopolitan genera. Most of the species are habit, habitat and distribution of these 230 specimens were sympatric with wide dibtribution ranges. However, each carefully studied and a tentative key was compiled. All the species is restricted to a particular habitat, a feature which remaining specimens were identified according to this can assist in identification. Unfortunately, taxonomic litera tentative key. Of these remaining specimens, the identity of ture seldom defines these habitats to the degree that is 67 were deemed tentative owing to poor specimens and 220 required for recognition in the field. were selected and identified using Tolken's (1967) keys as a Floral features form the basis of most taxonomic keys. test of the above-mentioned tentative key. However, the floral anatomies of many of the Salicornieae To study sclereids in the palisade tissue, Tolken (1967) are similar and seed, morphological and anatomical charac recommended the use of hand-cut sections. However, I ters are also used (Brenan 1988; Tolken 1967; Wilson 1980, found that the sclereids were extremely difficult to observe 1984). Because many of the specimens in herbaria lack in hand-cut sections. A freezing microtome was therefore flowers, these keys are not always easily applied. For this used to make 200 /-Lm thick cross- and longitudinal sections reason, Tolken (1967) produced a second key based on vegetative and anatomical features. These keys are not easy to use owing to difficulty in obtaining information about the specimen (e.g. the presence or absence of sclereids in the palisade tissue and their features) or because of poorly defined terms. Terminology The Salicornieae have a peculiar anatomy and some of the descriptive terms are confusing. The succulent parts of these plants are jointed and divided into longitudinal segments b containing chlorophyll. Although a number of theories have been proposed for the origin of this photosynthetic material, it is generally accepted as foliar in origin (Scott 1977; Talken 1967). It seems that these segments represent inverse, dorsi-ventrally opposite leaves which have enlarged and fused laterally. The abaxial sides of the leaves have c expanded vertically to cover the entire internode (Talken 1967). The adaxial side of this structure is fused to the stem. In other words, the bottom surface

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