Initiation of Procambial Strands in Leaf Primordia of Bread Wheat, Triticum aestivum L

Abstract

In Triticum aestivum L. the median and lateral procambial strands serving the primordia originate independently and in isolation from the vascular system of the rest of the plant. The median strand is initiated first, followed by a succession of lateral strands during the next four or so plastochrones. The median and first lateral strands have their point of origin in the axis, in the disc of insertion of the primordium. The later laterals are initiated up in the primordium. Once initiated the procambial strands extend from their point of origin both acropetally and basipetally, the latter extension eventually linking them to strands associated with older leaves. It would appear that the materials necessary for the growth of the apical dome and of the first four leaf primordia are supplied by general diffusion and not via direct vascular connexions with the rest of the plant.