Radial fibres in aggregate rays ofQuercus calliprinosWebb. – evidence for radial signal flow

Abstract

S U M M A R YRadial fibres differentiate in many aggregate rays of Quercus calliprinos Webb. The occurrence of radial fibres in rays suggests a radial flow of developmental stimuli for fibre differentiation.

Occurrence of radial sieve elements in the secondary phloem rays of some tropical species

“…The formation of fibers in the xylem rays of Quercus calliprinos is correlated with the radial signal flow operating in the regulation of rays (Lev-Yadun, 1994). Lev-Yadun and Aloni (1995) concluded that the formation of several radial ray centers within large vascular rays (polycentric aggregate rays) of Suaeda monoica reflects the establishment of several independent preferable pathways of radial signal flow within rays.…”

“…The occurrence of vascular elements (tracheids and vessels) in the radial direction in rays of mature wood of many species (Vliet, 1976;Botosso and Vidal Gomes, 1982;Carlquist, 1988;Fahn, 1990) further indicates that part of the radial signal flow is auxin and that its concentration is high enough to induce sieve or tracheary elements in the radial direction (Lev-Yadun and Aloni, 1995). In the present study, it appears that formation of the radial sieve elements in the rays of secondary phloem may also be associated with the radial signal flow (Lev-Yadun, 1994;Lev-Yadun andAloni, 1991, 1992).…”

“…Radial fibers are very infrequent; they have been reported in the rays of Monopteryx uacu (Papilionaceae) (Metcalfe and Chalk, 1950) and as libriform fibers in Cecropia (Carlquist, 1988). Radial fibers have also been reported in the aggregate rays of Quercus calliprinos Webb (Lev-Yadun, 1994), and axial and radial fibers have been reported in Cocculus hirsutus (Rajput and Rao, 2003). The occurrence of radial phloem strands has been reported in Azima tetracantha (Outer and Veenendaal, 1981), in Suaeda monoica (Lev-Yadun and Aloni, 1991), and isolated sieve tube elements have been reported in the rays of some tropical species Downloaded by [Universite Laval] at 06:37 06 October 2015 110 (Rajput and Rao, 1997).…”

“…Rays are usually composed of radial sheets of parenchyma but other elements, such as radial tracheids (Fahn, 1990), vessels (Carlquist, 1988), resin ducts (Fahn, 1990), fibers (Lev-Yadun, 1994), and sieve tubes (Lev-Yadun and Aloni, 1991;Rajput and Rao, 1997) can also be found in various species. Radial vascular elements are a rare feature, but they are more common in conifers, many of which have radial tracheids (Fahn, 1990).…”

Wood remains from archaeological excavations: A review with a Near Eastern perspective

“…The radial system (the vascular rays) is usually composed of parenchyma, although other cell types such as tracheids, resin and gum ducts, radial phloem, and radial fibers may infrequently be found in the rays (Fahn, 1990;Aloni, 1991a, 1995;Lev-Yadun, 1994b). Like the types of ring porosity mentioned above, the specific structure of the rays-(1) height in cell number, (2) width in cell number, (3) having radial resin or gum ducts, (4) having cells of only the same size and if not, their size variation, 5having radial components such as tracheids, fibers, and phloem, and being of two size categories (huge and small) as in oaks-is used for identification (e.g., Greguss, 1955;Fahn et al, 1986;IAWA, 1989IAWA, , 2004Schweingruber, 1990).…”