Soil Physical Environment and Root Growth in Northern Climates.

Abstract : Understanding the growth and function of plant roots in cold climates is critical, but examination of root systems to elucidate their link to production is expensive and labor-intensive. Limited information is available on the root growth and functions of plants grown in northern climates. Our objective is to present an overview of the influence of physical edaphic factors on plant root systems with special emphasis on models that are available for simulating root growth. This report summarizes the impact of the soil physical environment (soil water, soil temperature, soil air, physical impedance, and spatial variability) on root uptake and growth. Roots grow because new cells are formed in the meristematic tissue near the root tip, and these newly formed cells increase in volume, pushing the root tip forward if growth conditions are satisfactory. Rapid elongation of primary roots, combined with well-developed secondary roots, allows the plants to exploit moisture and nutrients from a greater soil volume. Root and shoots are strongly interdependent. The roots receive photo-synthates and growth hormones from shoots and in return furnish water and nutrients to the shoots. Several root growth models have been developed during the past decade; however, none addresses the problems associated with cold regions. The models reported in the literature can be classified as (1) simple models, (2) carbon partition models, (3) growing degree day-based models, (4) soil parameter-based models, and (5) arctic plant growth models.