Nutrient supply and plant growth

Abstract

By way of introduction, two general features of plant nutrition may be stated. Firstly, because all physiological processes in the plant are ultimately dependent upon the incorporation of one or more mineral nutrients in a form appropriate to underlying biochemistries, an increase in the size of plant organs and their correct functioning is ultimately dependent upon an appropriate availability of essential nutrients [15, 16, 21]. Secondly, the extent to which growth processes are dependent upon the current uptake of externally available nutrient will depend upon the amounts and availability of stored nutrients and the extent to which recycling occurs within the plant. Both storage and recycling are phenomena which can be of critical importance to the survival and fitness of individuals in nutrient deficient environments or under circumstances of fluctuating nutrient availability. In contrast to plantlets grown from cell culture, seeds can, for example, contain sufficient nutrients to allow considerable increase in plant size without further nutrient uptake. In micropropagated plantlets, the nutrient reserve will be minimal and current growth will predictably be largely dependent upon current availability and uptake of mineral nutrients. The first part of this paper discusses some basic relationships between nutrient supply and plant growth. The feasibility of controlling, in a quantitative manner, dry matter productivity by regulating the supply of any one mineral nutrient is emphasised. In the second part, qualitative differences in growth response dependent upon the nature of nutrient limitation are discussed. It is suggested that, by combining quantitative and qualitative aspects, plants of a predictable size, morphology, physiology and biochemistry may be grown. It is believed that this could have particular bearing not only on the commercial preparation of plantlets of a given size and appearance but also on the subsequent production and recovery of specific metabolites from plants whose micropropagation has, from the outset, been combined with appropriate nutritional practice.