PLANT NUTRITION AND GROWTH - BASIC PRINCIPLES

Strictly controlled experiments with plants, acclimatized under steady-state conditions and grown for a sufficiently long time period to get reliable and representative measurements, are necessary to obtain plant responses in precise terms (reference values). It is then possible to reproduce and compare experimental results with a high accuracy and to establish fundamental plant properties in an unambiguous and unifying terminology. Two kinds of growth determining factors can be distinguished: 1) Mass transport, i.e. variables that express flux rates of carbon and mineral nutrients in relation to plant size and requirements (relative addition and uptake rates). These factors influence the relative growth rate, one at a time (Liebig's law of the minimum). 2) Factors that influence the mass transports, i.e. non-elemental resources, e.g. light and water availability, and modulators, e.g. genome, nutrient status and temperature. These factors interact in orthogonal relationships with each other and can be specified in normalized terms when the optimum value is known.