Aliso: A Journal of Systematic and Evolutionary Botany Volume 16 | Issue 2 Article 9 1997 Wood Anatomy of Portulacaceae and Hectorellaceae: Ecological, Habital, and Systematic Implications Sherwin Carlquist Santa Barbara Botanic Garden Follow this and additional works at: http://scholarship.claremont.edu/aliso Part of the Botany Commons Recommended Citation Carlquist, Sherwin (1997) "Wood Anatomy of Portulacaceae and Hectorellaceae: Ecological, Habital, and Systematic Implications," Aliso: A Journal of Systematic and Evolutionary Botany: Vol. 16: Iss. 2, Article 9. Available at: http://scholarship.claremont.edu/aliso/vol16/iss2/9 Aliso, 16(2), pp. 137- 153 © 1998, by The Rancho Santa Ana Botanic Garden, Claremont, CA 9 17 11 -3 157 WOOD ANATOMY OF PORTULACACEAE AND HECTORELLACEAE: ECOLOGICAL, HABITAL, AND SYSTEMATIC IMPLICATIONS SHERWIN CARLQUIST1 Santa Barbara Botanic Garden 1212 Mission Canyon Road Santa Barbara, CA 93105 A BSTRACT Qualitative and quantitative wood data are given for 13 species of 10 genera of Portulacaceae (secondary xylem from additional species of Anacampseros and Lewisia were studied but not quan­ titatively analyzed). Most Portulacaceae show modifications that can be related to the succulent habit, including wide, tall rays mostly composed of thin-wall ed cells; total or partial substitution of axial parenchyma for libriform fibers ; and modified patterns of pitting on lateral wall s of vessels. Pseudo­ scalariform pitting is more common in Portulacaceae than in other dicotyledon families. In vessels of Anacampseros wood, wide helical bands of secondary wall materi al are present. Similar helices (but without the unusual width) occur in the wood of Lewisia and Heclorella. Woods of Portulacaceae as a whole are markedly xeromorphic with respect to vessel e lement dimensions, vessel density, and vessel grouping; wood of Lewisia and Hectorella is especiall y xeromorphic. Xeromorphism is not so pronounced in succulent dicotyledons at large. Woods of species of Portulacaceae with less marked adaptation to succulence show close resemblance to woods of Didiereaceae and woodier Cactaceae, suggesting the validity of the suborder Portulacineae, which includes these three families plus Hec­ torellaceae and Basellaceae. The wood of Heclorella is very similar to that of Lewisia rediviva and contains no features not also observed in Portulacaceae. Tracheidlike idioblasts in rays of Anacamp­ seros are likely not homologous with wide-band vascular (or vasicentric) tracheids in fascicular sec­ ondary xylem of globular cacti. Dark-colored mucilage idioblasts in Portulacaceae are likely to be a homoplasy; they occur in a scattering of Caryophyllales. Key words: Caryophyllales, Centrospermae, ecological wood anatomy, Portulacineae, succulence, tracheoidal idioblasts, xeromorphic wood. INTRODUCTION ophyllales. Metcalfe and Chalk (1950) summarized data on wood of several species of Portulacaceae, both The present paper continues a series of studies on data obtained by them and data from other authors. wood anatomy of Caryophyllales (Centrospermae of Gibson (1994) added some qualitative details for sev­ earlier authors) begun with a survey of woods of Cary­ eral species of Portulacaceae. The paucity of infor­ ophyllaceae (Carlquist 1995a). Some caryophyllalean mation relates partly to the nonwoody nature of most families, such as Cactaceae, have been studied exten­ species of the family. Studies on wood anatomy have sively by other authors and will not be covered in this traditionally emphasized woody species while neglect­ series. The work of these authors, however. will be cited in the concluding paper of this series. The wood ing herbaceous species. Another reason for neglect of of a family now widely regarded as an outgroup of wood anatomy of Portulacaceae is the worldwide dis­ Caryophyllales, Plumbaginaceae, has been surveyed tribution of the family: a comprehensive collection of recently (Carlquist and Boggs 1996). Polygonaceae are wood samples is thereby difficult to obtain, and wood widely regarded as an outgroup of Caryophyllales and samples must be preserved in liquid for shipment. a sister family of Plumbaginaceae (Rodman et al. Wood samples of dicotyledons are traditionally pre­ 1984; Giannasi et al. 1992; Rettig et al. 1992; Downie served by drying, but succulence is extensive in Por­ and Palmer 1994; Williams et al. 1994; Downie et al. tulacaceae and the family is thus little represented in 1997). A survey of wood anatomy of Polygonaceae is xylaria. One of the reasons for studying the wood anat­ planned. omy of Portulacaceae is that it demonstrates various Despite the fact that CaryophyUales are one of the kinds of stem succulence, and shows how wood of a best studied orders of angiosperms (Mabry 1977; group of dicotyledons has become modified to accom­ Behnke and Mabry 1994), relatively little attention has modate water storage and mechanical strength to di­ been paid to wood anatomy of most families of Cary- vergent degrees. The present study is not maximally comprehensive I Address all correspondence to author at 4539 Via Huerto, Santa for the family, which is relatively large (19 genera, 500 Barbara, CA 93110-2323. species: Cronquist and Thorne 1994). However, a large 138 Carlquist ALISO proportion of the family is herbaceous. An attempt is cies, woods were treated with ethylene diamine, em­ made here to study a sampling of the woodier repre­ bedded in paraffin, and sectioned on a rotary micro­ sentatives and, by way of comparison, some herba­ tome (Carlquist 1982). Strength of ethylene diamine ceous species. Wood of the cushion-plant family Hec­ solutions and length of exposure to this chemical var­ torellaceae (Hectorella caespitosa on New Zealand ied with softness of a given wood. and Lyallia kerguelensis Hook f. on Kerguelen: Phi­ Sections were stained with a safranin-fast green lipson 1993) has not been studied hitherto. Hectorel­ combination corresponding to Northen's modification laceae were included within Caryophyllaceae earlier of Foster's tannic acid-ferric chloride method (Johan­ (Pax and Hoffmann 1934), although some more recent sen 1940). Some paraffin sections (e.g., Fig. 25) were authors have included the family in Portulacaceae mounted on aluminum stubs, cleansed of paraffin, (Cronquist 1981; Rodman 1994). Cronquist and sputter coated, and examined with scanning electron Thome (1994) recognize Hectorellaceae as a family, microscopy (SEM). Macerations were prepared by but concede they deliberately use narrow definitions of means of Jeffrey's Fluid and stained with safranin. families for convenience in referring to segregate fam­ Sources of the specimens were as follows: Ana­ ilies. Hectorella contains betalains (Yoong et al. 1975; campseros alstoni Schonl., Carlquist 8169 (SBG), cul­ Mabry et al. 1978) and thus clearly belongs to Cary­ tivated, Santa Barbara; A. alta Poelln., Carlquist 8167 ophyllales. The family has not been included in recent (SBG), cultivated, Santa Barbara; A. densifolia Dint., studies on molecular systematics, but its inclusion cultivated, Huntington Botanical Gardens (H-44401); within the suborder Portulacineae seems very likely on A. marlothii Poelln., cultivated, Huntington Botanical the basis of macromorphology. Gardens (H-46898); A. retusa Poelln., cultivated, Hun­ Although cladograms based on macromorphology tington Botanical Gardens (H-23384); A. telephiastrum and on DNA studies are not entirely in agreement, the DC., Carlquist 8168 (SBG), cultivated, Santa Barbara; closeness of Portulacaceae to Didiereaceae and to Bas­ Calyptrotheca somaliana Gilg, cultivated, Huntington ellaceae is often emphasized, and Cactaceae are usu­ Botanical Gardens (H-57630); Ceraria Jruticulosa ally placed near this trio of families (e.g., Rodman Pears. & E. L. Stephens, Carlquist 8170 (SBG), cul­ 1994). One of the purposes of the present study is to tivated, Santa Barbara; Cistanthe guadalupense (Dud­ offer data concerning the five families of Portulacineae ley) Carolin ex Hershkovitz, Carlquist 480 (RSA); and to determine whether wood data are in accord with Hectorella caespitosa Hook. f., Old Man Range near this grouping. Assuming this suborder as a natural Alexandra, central Otago, South Island, New Zealand, group, what kinds of wood diversification have oc­ Beckstrom 1098 (RSA); Lewisia cantelovii Howell, curred? cultivated, Rare Plant Research, Portland, Oregon; L. Habit is of.overriding significance in interpretation cotyledon (Wats.) Robinson var. howellii (Wats.) Jeps., of wood patterns. Portulacaceae range from woody summit of Siskiyou Mountains, 3 km SW of Dry Lake, shrubs (Portulaca ria, Talinella) or subshrubs (Tali­ Lookout, Siskiyou Co., California, Ownbey 1751 num, Talinopsis) that have succulent to semi succulent (RSA); L. rediviva Pursh, Carlquist 8157 (RSA), tree­ leaves and stems to very succulent sub shrubs (Cistan­ line, Mt. San Antonio, Los Angeles County, Califor­ the) or rosette herbs that are succulent in texture (Lew­ nia; L. rupicola C. S. English, cultivated, Rare Plant isia). The diverse types of wood in Portulacaceae must Research, Portland, Oregon; Portulaca sp., cultivated, be examined first in terms of habit and ecology. Dif­ Huntington Botanical Gardens (H-54247; native to Ke­ ferences that do not appear correlated with these di­ nya); Portulacaria aJra Jacq., cultivated, Claremont, verse habits may be considered within systematic con­ California; P. armiana E. V. van Jaarsveld, cultivated, texts. Huntington Botanical Gardens (s.n.); Talinella