Growth activity of fusiform initials in storeyed cambium

The intrusive growth of fusiform initials was studied in Entandrophragma, This growth makes possible a change in the position of the cell ends of one storey in respect to those in the neighbouring storey, and this is 'turn leads to changes in the orientation of cambial initials. The growth activities of the oppositely directed ends of the same initial are not the same. Not all cell ends are simultaneously actiye. There are groups of ends distributed alternately in a storey which are active or inactive, so that a pattern of growth activity appears in the cambium. The activity of a particular cell end changes in successive time periods. Owing to this, the rate of creeping of one end past. those of the adjoining storey varies. This phenomenon of changes in the activity of cell ends in time may be referred to the phenomenon of the appearance of the growth activity pattern on the cambium surface under the hypothesis of transverse shifting of the elements of this pattern ("active" and. "inactive" groups) in relation to the cambial initials

Mechanism of changes in grain inclination in wood produced by storeyed cambium

The changes in cell orientation in the cambium of Entandrophragma producing wood with interlocked type of grain, and in the cambium of Tilia in a spirally girdled stem are traced through serial tangential sections of wood. In Entandrophragma the changes result from the intrusive growth of a fusiform cell whih repeatedly produces a new pointed tip from one side of the existing tip which disappears. This causes a sort of creeping of cell ends of one storey past those of the adjoining storey. The oppositely directed ends of the cells belonging to one storey creep in opposite directions so that the position of the cell centres remains constant and only the angle between the cells and the stem axis changes. The stratification of short rays in Entandrophragma represents an adaptation to the changes in celi orientation involved in the formation of interlocked grain. The mechanism of changes in grain inclination in Tilia is intermediate between that based on the creeping of cell ends and that based on pseudotransverse division and intrusive elongation which is known in non-storeyed cambia

Biophysical optimality of the golden angle in phyllotaxis

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