Abstract
Young stems of Aerva javanica (Burm.f.) Juss. ex Schult., A. lanata (L.) Juss. ex Schult, A. monsonia Mart., A. sanguinolenta (L.) Blume, Alternanthera bettzickiana (Regel) G. Nicholson, A. philoxeroides (Mart.) Griseb., Gomphrena celosioides Mart., G. globosa L. and Telanthera ficoidea (L.) Moq., showed the renewal of small sectors of cambium by replacing with new segments. Therefore, the secondary phloem formed by earlier cambial segments form isolated islands of phloem enclosed within conjunctive tissues became embedded in the secondary xylem. As the stem grows older, complete ring of cambium is renewed; sometimes an anastomosing network of successive cambia may be seen due to the renewal of larger segments of the cambium. Renewal of the cambium takes place by repeated periclinal division in the parenchyma cells positioned outside to the phloem formed by the previous cambium. Functionally the cambium is bidirectional and exclusively composed of fusiform cambial cells. Differentiation of conducting elements of the secondary xylem and phloem remains restricted to the certain cambial cells while rest of the segments exclusively produce conjunctive cells. Accumulation of starch along with the presence of nuclei in the xylem fibers even after deposition of the secondary wall is consistent in all the species and it seems to be associated with the absence of rays in the secondary xylem and phloem of nine species from four genera. The significance of successive cambia, rayless xylem and nucleated xylem fibers were correlated with plant habit.
Highlights
Families like Amaranthaceae, Chenopodiaceae, Nyctaginaceae, Phytolccaceae etc. from the core Caryophyllales are well recognized in literature for their unique pattern of secondary growth
Successive rings of cambia initiate external to the phloem produced by the regular vascular cambium (Fig. 1C, D & F)
Development of successive cambium: As a characteristic feature of Amaranthaceae, all the species investigated in the present study showed that the vascular cambium ceased to divide after producing a limited amount of secondary xylem (i.e. 500-700 μm, in G. celosioides and 1-2 mm in rest of the species)
Summary
Families like Amaranthaceae, Chenopodiaceae, Nyctaginaceae, Phytolccaceae etc. from the core Caryophyllales are well recognized in literature for their unique pattern of secondary growth. From the core Caryophyllales are well recognized in literature for their unique pattern of secondary growth. Development of successive cambia takes place from the parenchymatous cells positioned outside to the primary phloem of each vascular bundle. An. Horizon e-Publishing Group opinion regarding the origin of successive cambia, structure and composition of its derivatives varies among different workers [1,2,3,4,5,6,7,8,9,10]. Nearly 65 synonyms are reported to be available in the literature [11] on the meristem on this group. Schinz [3] mentioned that an increase in stem diameter and production of secondary vascular tissue in Amaranthaceae takes place by successive cambia that divide for a limited period
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