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The Reproductive Strategy of Higher Plants: II. The Reproductive Strategy of Tussilago Farfara L.

John Ogden
Journal of Ecology
Vol. 62, No. 1 (Mar., 1974), pp. 291-324
DOI: 10.2307/2258894
Stable URL: http://www.jstor.org/stable/2258894
Page Count: 34
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The Reproductive Strategy of Higher Plants: II. The Reproductive Strategy of Tussilago Farfara L.
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Abstract

Three experiments are described in which the partitioning of dry matter and calories was monitored in the rhizomatous perennial Tussilago farfara. The experimental treatments involved levels of soil fertility and plant density, in field plots and wooden boxes. In all the experiments sequential harvests were taken and the plants were divided into their component structures, dried and weighed. Dead matter was collected, and the shed seed yield obtained from the linear regression of seed yield on receptacle weight. The quantity of dry weight allocated to vegetative reproduction was obtained by weighing the rhizomes when their weight was lowest, during spring. At high plant densities the proportion of the total accumulated net production constituting biomass at any time was reduced. This is attributed to the skewing of the individual size frequency distribution, resulting in greater mortality rates at high density. The size frequency distribution of the flower clusters, flower bud mortality and mean capitulum size, all show compensatory responses to density, minimizing differences in seed yield per unit area. Diagrams showing the pattern of dry weight partitioning over two seasons are presented. Emphasis is given to examination of the proportionate, rather than the absolute, amounts of dry weight allocated to different structures under different conditions. `Sexual reproductive effort' was in the range 3-8% of the total annual net production. `Vegetative reproductive effort' showed greater variability, ranging from 4 to 23% under different treatments. These figures are similar to those of some other perennial rhizomatous herbs. Total investment in reproduction by rhizomatous perennials is supposed to be similar to that in seral annuals, although in the latter this investment is in seeds only. Total rhizome yield was greatest in fertile soil, but as a proportion of the total production it was greatest in poor soil. It is suggested that, as the density of a T. farfara clone increases, reproductive tactics tend to favour seed production relative to vegetative spread. It is concluded that the responses observed represent adaptations to life in open habitats of low fertility situated in localities which experience severe winters and short growing seasons.

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