Portal de Periódicos da CAPES

Comparative Anatomy of the Leaf-Bearing Cactaceae, IX: the Xylem of Pereskia grandifolia and Pereskia bleo

1963; Arnold Arboretum of Harvard University; Volume: 44; Issue: 2 Linguagem: Inglês

10.5962/p.185665

2474-3283

Irving W. Bailey,

Botany, Ecology, and Taxonomy Studies

PERESKIA BLEOThk two spkcif.s of Pcrcskia treated in this paper./'.gnindi folia Haw. and P. biro DC., have been considered to he closely related, the former occurring in Brazil and the latter in northwestern South America and Panama.It is of interest in this connection that Dr. Rodriguez reports (personal communication) that trees closely resembling P. biro occur in dense forests at elevations of 1400 meters in Costa Rica.He is convinced that these trees, now growing in the wild, do not belong to a species which was originally introduced by man and subsequently escaped from culti-These putative species, which may ultimately prove to be geographical races of a single species, are woody shrubs or small trees which may attain a height of live to seven meters at maturity.When growing in isolation they tend to form a single main stem or trunk which may attain a diameter of ten centimeters or more.However, as in the case of other leaf-bearing cacti their form may be modified by close crowding in hedges and by pruning or other mutilation by man.The xylem of Pcrrskia vjaudpolia and /'.hit o exhibits similar ranges of anatomical variability, which in turn closely resemble those that occur in the xylem of /'.sacharosu Griseb.(Bailey.1962).The vessels occur singly and in small clusters (Figs.12345678).Although commonly diffusely distributed, particularly in the hrst-formed secondary xylem, the vessels may at times be aggregated into more or less conspicuous zonal or concentric patterns (Figs.1,2,3).However, in some cases appearances of zonation are due solely to varying intensities of lignilication in the thick secondary walls of the libriform fibers (Fig. 8).The libriform fibers which may be septate or nonseptate function in the storage of starch.The wood parenchyma is scanty paratracheal (Figs.5678).The abundance and width of the multiseriate rays, as seen in transverse sections of stems and roots (Figs.1234), are highly variable, those of the roots tending to broaden more precociously and extensively than those of the stem, as in Pcrrskia sar/iarosa.The particular structural details (illustrated in Figs. 1 and 2) of P. gramlijol'ia and (Figs. 3 and4) of /'.biro do not provide reliable diagnostic criteria lor differentiating the :