New Zealand Journal of Botany abstracts

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Developmental Changes in the Vascular Cambium of Aeschynomene hispida Willd.

B. G. BUTTERFIELD

Botany Department, University of Canterbury, Christchurch

Abstract Developmental changes in the vascular cambium of Aeschynomene hispida Willd. were determined from an analysis of transverse and tangential longitudinal sections of the secondary xylem. Increase in the number of fusiform cambial initials in this plant is brought about by two types of anticlinal division. The majority of these divisions are radial longitudinal, contributing to the number of fusiform cells in the tangential plane. Occasional transverse division of fusiform initials can add cells in the vertical plane. Apart from a slight rearrangement of the cell tips, there is no intrusive growth of the daughter cells following either type of division. Repeated radial longitudinal divisions produce a highly developed storeyed pattern of the fusiform initials when viewed in tangential section, following radial growth. The frequency of radial longitudinal division, recorded as a percentage of the fusiform initials that divide for each millimetre of radial growth, declines with radial distance from the stem centre. The mean length of the fusiform initials remains fairly constant with radial growth, but the tangential width of these cells increases rapidly over the first 10 mm and then remains constant. An apparent deficiency in the frequency of anticlinal division over the first few millimetres of radial growth is compensated for by an increase in the tangential dimension of the fusiform initials. No loss of fusiform initials occurs other than that resulting from their transformation into ray initials. Both uniseriate and multiseriate ray initials generally occupy similar tangential dimensions to neighbouring fusiform initials. New rays develop by the subdivision of individual fusiform initials. The secondary xylem produced by the cambium is unusual in that the axial parenchyma cells, vessel members, and fibres all remain largely within the confines of the storeys.

Received 20 October 1971

PDF file of entire paper: medium quality (2115K); (scanned from paper original: notes about this process)

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