Apical intrusive growth of cambial fusiform initials along the tangential walls of adjacent fusiform initials: evidence for a new concept

Abstract

A new study of cambium of Pinus sylvestris L., Tilia cordata Mill. and Wisteria floribunda (Willd.) DC provides fresh clues on the cambial dynamics, rejecting the hitherto held concept that intrusive growth of the fusiform initial occurs between the radial walls of adjacent initials. It demonstrates that intrusion of the elongating initial in fact takes place along tangential walls of adjacent fusiform initials and their immediate derivatives. It also suggests a new mechanism for ‘elimination of initials’. Intrusive growth of the fusiform initial was found to begin with development of characteristic slants, representing a transitional stage of the process of transformation of periclinal walls of fusiform initial cells into radial walls, as observed in transverse sections of active cambium. The gradually progressing event comprised (a) appearance of either a triangular microspace limited by two periclinal walls of a fusiform initial and its derivative and one radial wall of another fusiform initial in the adjacent radial file, or a rhomboidal microspace enclosed by four periclinal walls of two laterally adjacent fusiform initials and their immediate derivatives, (b) intrusion of elongating tip of fusiform initial from neighbouring file into the microspace thus formed, (c) symplastic growth of the cambial cell walls in radial direction, (d) unequal periclinal divisions of fusiform initial cells while growing intrusively, and (e) unequal periclinal divisions of derivative cells not growing intrusively. Intrusive growth between periclinal walls affected rearrangement of the fusiform initials but did not add to the cambial circumference. The existing concepts of (a) intrusion of the fusiform initial between radial walls of neighbouring initials and (b) elimination of fusiform initials from cambial surface have been reassessed and redefined.

PaCeQuant: A Tool for High-Throughput Quantification of Pavement Cell Shape Characteristics

“…6B). Thus, consistent with earlier studies, our data suggest that type II lobes are established mostly during cytokinesis, while most of the lobes formed during cellular expansion are type I lobes (Jura et al, 2006;Wu et al, 2016).…”

“…During development, the difference between the two nonuniformly growing parts of the lobes increased further. Our results suggest that predominant expansion of one the two neighboring cells contributes to the higher degree of asymmetric expansion at type II lobes, which is consistent with previous reports (Jura et al, 2006). Together, we conclude that our novel method robustly detects and Figure 6.…”

“…6). These differences might be caused by higher growth rates of one of the two neighboring cells, which is consistent with earlier reports (Jura et al, 2006). The optional analysis of lobe types implemented in PaCeQuant thus provides the first tool to study effects of gene functions specifically involved in the formation of three-cell junctions and to measure shape characteristics of individual lobes.…”

Mathematical Modeling of Intrusive Growth of Fusiform Initials in Relation to Radial Growth and Expanding Cambial Circumference in Pinus sylvestris L.

“…The mechanism of increase of the cambial cylinder, as explained by Bailey (1923) and accepted by the subsequent plant anatomists, is unable to accommodate certain facts such as: (a) The distinction between non-storeyed and storeyed types of cambium is not always clear and some species have mosaics of non-storeyed and storeyed cambia (Krawczyszyn 1977); (b) In cambia with short fusiform cells both types of multiplicative divisions (oblique and radial longitudinal) co-exist and a distinction between them is often arbitrary (Krawczyszyn 1977), and (c) Both the intrusive and symplastic growths take place in both the storeyed and the non-storeyed cambia (Jura et al 2006). Moreover, in order to contribute to increase in the surface of the cambial cylinder, intrusive growth has to occur along the radial walls of contiguous cells.…”

LobeFinder: A Convex Hull-Based Method for Quantitative Boundary Analyses of Lobed Plant Cells

“…growth mechanism that generates a type II lobe may resemble intrusive growth (Jura et al, 2006), in which one cell expands asymmetrically at the interface of two adjacent cells. This form of asymmetric growth likely differs from that which generates lobes that are independent of tripartite junctions.…”