2017 ASHS Annual Conference

Below ground systems remain one of the most poorly understood areas in terrestrial ecology. The life histories are different between perennial and annual plants and that contributes to difficulties establishing perennials on lands dominated by annuals. The main objective of this work was to determine if the root structure and the rate of root development differed between annuals and perennials. The competitive growth rates among annuals and perennials from initial germination and growth to nine weeks were evaluated as well. Seeds of 7 spices, Helianthus annuus (sunflower), Machaeranthera (Aster) tanacetifolia, Chenopodium berlandieri (chenopodium), Amaranthus retroflexus (amaranthus), Atriplex canescens (4-wing saltbush), Aquilegia caerulea (columbine), and Gaillardia aristata (gaillardia) were germinated at Colorado State University Plant Growth Facilities and grown for nine weeks. Length, surface area, and volume of the roots were measured as well as biomass for both the root and shoot system. The results demonstrated significant variation among species in most traits. In weekly biomass comparisons, Amaranthus retroflexus showed the greatest biomass followed closely by Helianthus annuus. Both Amaranthus retroflexus and Helianthus annuus are annuals whereas the perennials Aquilegia caerulea and Atriplex canescens had the lowest weekly biomass. Annuals had significantly greater root length and surface area, whereas only Gaillardia aristata of the perennials evaluated had the largest root volume when compared to other species followed by Helianthus annuus and Amaranthus retroflexus (annuals). Competitive growth among species indicated that the annual, Amaranthus retroflexus, had superior biomass among species at nine weeks whereas the Aquilegia caerulea, perennial, had the lowest amount of biomass. In conclusion, annuals have the greater growth rate. The size, structure and the length of the root system can give annuals the ability to forage the nutrients more quickly than perennials. This growth strategy allows them to quickly capture available resources and complete their life cycle which may serve to suppress competitors.