Comparative analysis of architecture formation process between Viburnum dilatatum and V. wrightii(Caprifoliaceae)

Abstract

Process of architecture formation was quantitatively analyzed for Viburnum dilatatum and V. wrightii(Caprifoliaceae). In both species, orthotropic primary axes emerge from the basal parts of mother plants near the ground level. Terminal buds of vegetative shoots and paired axillary buds on the most distal nodes of reproductive shoots elongate dominantly in the following year. The architecture of the primary axes is formed by four branching patterns: a monopodial pattern(M), a sympodial pattern producing a pair of opposite daughter shoots(SP), a sympodial pattern producing a single daughter shoot(SS), and a pattern terminated with a dormant or dead bud(D). Process of the architecture formation is composed of four successive stages: 1)height growth, where the M pattern is dominant; 2)crown formation, the M pattern decreased gradually, while the SP and SS patterns occur; 3)crown expansion, the M and SP patterns are frequent; 4)over mature, the M pattern becomes dominant again. The primary axes grow vigorously only within a first few years of their development. Axillary buds of them emerge after several years' dormancy and form orthotropic secondary axes. For Viburnum dilatatum, nearly50%of the primary axes develop the secondary axes, and the secondary axes also elongate vigorously. Furthermore, more than20%of the secondary axes form the tertiary axes, and only10%of the tertiary axes form the quarternaryaxes. On the contrary, only less than25%of Viburnum wrightiis primary axes form the secondary axes which do not elongate vigorously. This speceis entirely does not form tertiary axis. Consequently, Viburnum wrightii forms more simple architecture than V. dilatatum.