Growth potentials ofTaraxacummicrospecies from different habitats

Abstract

Various Taraxacum microspecies from different fertile habitats were cultured at near optimal conditions in order to study the relationship between growth potential and habitat as a factor in their distribution, taking a high growth rate as essential for the occupation of fertile sites. Differences in relative growth rates between microspecies from fertile and infertile sites were most clear during early vegetative growth and mounted up to approximately 30%. During this stage, the high relative growth rates of microspecies from fertile sites were due to a combined effect of a high leaf area ratio and a high unit leaf rate. Differences in relative growth rates between microspecies from intermediate fertile and infertile sites were small or even absent. In this stage of vegetative growth, growth parameters were rapidly changing: relative growth rate and unit leaf rate declined with age while specific leaf area and/or leaf weight ratio, and thus leaf area ratio, increased; these changes were most pronounced in fast-growing microspecies. During later stages of vegetative growth, differences in relative growth rate between some microspecies occasionally diminished, but microspecies differences in morphology (i.e. leaf weight ratio and specific leaf area) were maintained or even increased. Within the group of the studied slow-growing microspecies, derived from infertile and/or dry sites, the low leaf area ratio was primarily due to a low leaf weight ratio. In microspecies with a high leaf area ratio, with a flat and dense rosette, unit leaf rate was depressed due to effects of self-shading.