Nonparallelism of cambium celles in neighboring rows

Abstract

The periclinal walls of camlbial cells in neighboring lineages (rows) may not be parallel when viewed in their radia! aspect. This lack of iongitudinal parallelism may be so extensive that in active cambium pairs of cells from neigltbor,ing rows may be in contact only aJong restricted segmentJ. This means that the initlial cells, ratheir than forming a collltinuous \ayer, may be arranged in an irre,gular ne'twork pa:ttern from wltich some parts ,project i111war,d or outward firom the layeir of their mutual conta•cts. The longitu•dina•l nonparallelism of cambial cells bocomes more pronounced during symplast.ie radia! growth. Unequal periclinal div:sions counteract this, and in initial cells abscission of the parts projecting f.rom the layer of mutual contact oocurs. When the cambium paŚses from a period of activity to a period of rest a continuous laye.r of initials is recstabhshed. Thi, involves elongation by intrusi'llle growlth df those ceHs prev.iously shortened as the result of i,nregular periclinal di,v,isions. The division walls in cambial cells may be wa.rped, that is they change thclr orientation alon,g the longitudinal direction pe.rhaps even similau- to an aircraft propeller. A division wali may thus be periclinal in one part of the cell and antticlinal in another.