Flora (1999) 194 1—12 © by Urban & Fischer Verlag Wood, stem, and root anatomy of Basellaceae with relation to habit, systematics, and cambial variants SHERWIN CARLQuIsT Santa Barbara Botanic Garden, 1212 Mission Canyon Road, Santa Barbara, California 93105 U.S.A. Accepted: June 24, 1997 Summary Wood data from wider stem, root, and root-stem transition of a mature plant of Anredera baselloides are analyzed for quantita tive and qualitative features. Distinctive characters of A. baselloides include presence of successive cambia in wider stem, root, and root-stem transition; other types of cambial variants are newly reported for the family. Systematic distribution of successive cambia in Caryophyllales does not parallel cladistic schemes for the order, and possible reasons are advanced. Wood features other than successive cambia are compatible with relationship to the other families of Portulacinae (Cactaceae, Didiereaceae, Hectorellacaeae, Portulacaeae) except for features related to habit, particularly the scandent habit. These features (mostly newly reported for Basellaceae) include restriction of vessels to central portions of fascicular areas (vessels thereby likely protected from torsion); some vessels wide but many narrow; all ray cells and ray-adjacent axial parenchyma with thin walls; (inter xylary) phloem strands in ray-adjacent axial parenchyma (with cambia that augment the phloem strands); and intraxylary phloem. Tubers contain pith phloem strands adjacent to which cambia produce secondary xylem and phloem. Druses and mucilage cells in cortex and rays and storying in axial xylem cells are newly reported for Basellaceae. Key words: “Anomalous” secondary growth, cambial variants, Caryophyllales, Centrospermae, lianas, successive cambia. 1. Introduction TH0RNE 1994, NowicKE 1994, 1996), which is usually construed as containing Cactaceae, Didiereaceae, Hec The family Basellaceae (4 genera, 40 species: CR0N- torellaceae, and Portulacaceae. R0DMAN et al. (1984) QUIST & TH0RNE 1994) is of special interest within and R0DMAN (1994) made a case for inclusion of Aizo Caryophyllales in a number of respects. All species are aceae in the same dade as the families of Portulacineae vining or lianoid, a habit relatively unusual in the order, (but see MANHART & RETTIG 1994). although found in agdestoid and petiverioid Phytolacca Cactaceae, Didiereaceae, Hectorellaceae, and Portu ceae, Bosea (Amaranthaceae), Bougainvillea (Nycta lacaceae lack successive cambia (METcALFE & CHALK ginaceae), and a few species of pereskioid cacti. The 1950, RAuH & DITTMAR 1970, GIBsoN 1994, CARL family is also distinctive in its tubers, which are not like QUIST 1998). Anredera baselloides (H. B. K.) BAILL0N, stems elsewhere in Caryophyllales. The stems, roots, Basella rubra L., and Ullucus tuberosus CALDA5 of and tubers are capable of indefinite longevity in some the Basellaceae were reported to have successive species, such as the one studied here, Anredera basello cambia (M0R0T 1884, PFEIFFER 1926), and successive ides, for which an unusually mature specimen was avail cambia are mentioned for the family by PANIKKAR & able. Numerous anatomical characteristics of wood, BHAMBIE (1974); more recent authors have not men stems, and roots are reported for the first time because tioned these reports. In addition, cambial variants other of the excellence of this material. Only stems of limited than successive cambia are present in A. baselloides diameter were available to METcALFE & CHALK (1950) and are described below. The distribution of successive and GIBsoN (1994). cambia in Caryophyllales is of considerable potential The likelihood that wood anatomy is strongly in phyletic significance: about half of the families and fluenced by the scandent habit of Basellaceae provides genera of the order have successive cambia, but the problems in systematic interpretation in wood anatomy. systematic distribution of these taxa does not cor Basellaceae have been placed in the suborder Portulaci respond in a parsimonious fashion with the position of neae (TH0RNE 1992, BEHNKE 1994, CR0NQuIsT & these taxa in cladograms. Therefore, successive cambia 0367-2530/99/194/01-001 $ 12.00/0 FLORA (1999) 194 1 present a curious situation in the interpretation of phy The mature specimen that forms the basis for the descrip lesis of Caryophyllales. Genetic, developmental, and tions below is clearly referable to Anredera base//aides functional nature of successive cambia in the order are = Boussingaultia base//aides H. B. K. and Anredera scandens in need of elucidation, and Basellaceae are central to (L.) M0Q.j. This plant was supplied to me by STEVE MoRGAN analysis of these questions. In Caryophyllales, succes (Botanic Garden, University of California at Riverside), it was probably at least 40 years old, and had been cultivated at a sive cambia can be found in succulent roots (Caryo residence in La Verne, California. The portions designated as phyllaceae, Chenopodiaceae, Nyctaginaceae: PFEIFFER “upper Stems” were not twigs but upper portions of the main 1926, METcALFE & CHALK 1950) as well as lianoid stem, about 2 cm in diameter. The root-stem transition features stems (Nyctaginaceae: EsAu & CHEADLE 1969) or in a swollen form, wider than the stem above this region and stems subshrubs (Halophyttim: GIBsoN 1978) or trees aboLit 10cm in diameter. The root selected for sectioning was (Phytolaccaceae: WHEAT 1977, MIKEsELL 1979), so a portion of the main root about 5 cm in diameter. The tubers factors other than habit must be involved. Caryophylla are potato-like branches from the main stem at ground level, les in general, and Basellaceae in particular, are keys to and were about 3 cm in diameter in the plant studied. Stem and understanding of structure, functional significance, and root materials of relatively large specimens identified as Bous phylogenetic nature of successive cambia in vascular singaultia cordiftlia TEN0RE and B. gracilis MIERs were plants. available through the courtesy of the Los Angeles State and CountryArboretum, Arcadia, California. ULBRIcH (1934) con The materials studied here may all belong to a single cluded that these two taxa are conspecific with A. base//aides. species, A. haselloides (H. B. K.) BAILLON (see below). However, SPERLIN (1987) found that both B. cordij1ia and This is not regarded a limitation as to the present study, B . grad/is belong to a species separate from A. base//aides, the purpose of which is to establish the presence of par and that this species should be called Anredera cordi/ia ticular histological features father than to explore diver (TEN0RE) STEENIs. No anatomical differences (except those sity within the family. Anredera haselloides, however, due to dif-ferent degrees of maturity) were observed among may attain a large size than other species in the family, the col-lections studied here, so all are referred to A. hasel and thus may represent the nature of wood and cambial bides in accordance with ULBRIcH (1934). activity and other histological features in stems and Terms are according to the IAWA Committee on Nomen clature (1964). The term “vessel restriction pattern” roots better than immature material of other species. (CARL QUI5T 1983, 1988, CARLQuIsT & ZONA l988a) refers to pre New data on Basellaceae are important because a series sence of vessels in the central portions of fascicular areas, with of studies on Caryophyllales is in progress, and more libriform fibers adjacent to rays. In determining number of data on character states of these families are needed to vessels per mm2 of transection, ray areas were excluded from develop concepts of evolution of anatomical conditions the portions surveyed here. Had rays been included, the figu in the order. Data on Didiereaceae (RAuH & DITTMAR res for vessels per mm2 would have been much lower, especi 1970) and Cactaceae (several papers by GIBsON, see ally in tubers. Number of vessels per group is calculated as a GIBsoN 1994) have been contributed by others. The pre solitary vessel = 1.0, a pair of vessels in contact = 2.0, etc.; sent series includes a study of Caryophyllaceae (CARL however, the narrow vessels adjacent to wide vessels are so numerous that number of vessels cannot be accurately calcu QUIST 1995) and Portulacaceae (CARLQuIsT 1998), as lated. Vessel lumen diameter is measured an average well as a study of a family considered an outgroup of as be tween wide and narrow axes of a vessel lumen as seen in trans Caryophyllales, Plumbaginaceae (CARLQuIsT B0GGS & ection in order to present a more accurate image of the rheo 1996). logical capabilities of vessels. Both wide and narrow vessels were included in the means, although the two categories were also studied separately with respect to vessel element length. 2. Materials and methods Figs. 1—4. Photographs of sections of stem of Anredera base! All specimens were fixed in 50% aqueous ethanol; stems boides. 1—2. Transections. I. Section to show formation of a and roots of Basellaceae are too succulent for drying to be a second increment of vascular tissue (above) by a cambium feasible means of preservation. Liquid preservation is ad formed in the cortex; vascular tissue formed by the first cam vantageous in fixing thin-walled cells such as mucilage cells, bium below (sp = secondary phloem, sx = secondary xylem). phloem, and parenchyma, whereas woody dicotyledons have 2. Vascular tissue formed by cambium that originated in the wood that often consists wholly of cells with rigid lignified stem cortex; thin-walled axial parenchyma partially subdivi walls. Sections were prepared using the schedule of CARL des the fibrous portions of the secondary xylem. 3. Tangential QUIST (1982), in which ethylene diamine is employed as a sof section to show histology of fascicular area and ray portion tening agent prior to paraffin sectioning. Wide vessels and (dr = druse, lf= libriform fiber, mc = mucilage cell, wv = wider fibrous tissue embedded in a background of thin-walled tissue vessel). 4. Vessel wall from tangential section; grooves inter cannot be satisfactorily sectioned on a sliding microtome. Sec connect pit apertures (above). Fig. 1, scale above fig. 1 (finest tions were stained with a safranin-fast green combination.