Variations of growth in shoot apical domes of spruce seedlings : a study using the growth tensor

Abstract

Variations of the relative elemental rate of growth within apical domes, for the case when dome geometry changes during development, were modeled. It was ascertained that: I) the domes of spruce scedlings have a paraboloida! shape; 2) the shape is maintained during growth, but the domes become higher and widcr; 3) the relative elemcntal rate of growth in area on dome surface is isotropic, as indicated by analysis of cell packets in the surface layer. Thesc data wcre used in modeling by means of the growth tensor and natura) coordinate system. Growth of the dome was considered a superposition: I) of relatively fast steady shape growth, whcre the isotropy of growth in area on the surface of the dome, was determined, and 2) of relatively slow isogonic growth, which does not disturb the isotropy. The convergent parabolic system was selected as the natural coordinate system. Distributions of the growth rates in the form of computer-made maps for three doines differing in age, were obtained. lt appears that the growth rates within the dome are relatively high in the distal part and smaller in the cen tral and peripheral regions. This variation decreases progressively with seedling age when the dome becomes wider. The relative elemental rate of growth in volume, averaged for the whole dorne, also decreases.