The cotton plant ( Gossypium hirsutum) is a major accumulator of glycinebetaine. Under salinity stress glycinebetaine can make up to 10% of the plant nitrogen content, hence glycinebetaine accumulation has negative implications for the plants' energy and nitrogen economies, even under non-stress conditions. The external abiotic stresses, their signal transduction mechanisms, and the internal contributory factors that are involved in determining glycinebetaine concentration in leaves of cotton have hitherto not been investigated. Glycinebetaine is an important compound in the leaves of cotton, yet a definitive role under non-stressed conditions is not evident. The cotton plant is therefore an ideal system in which to characterise, perturb and then thereby rationalise glycinebetaine accumulation in plants. The factors that may be influential in determining glycinebetaine concentration in plants, i.e . growth retardation, translocation, degradation and de novo synthesis were investigated. These factors were investigated within the general context of the external abiotic stresses, salinity and nitrogen deficiency. It was found that a retardation of leaf growth, as occurs during osmotic stress in plants, does not result in a concentrating effect on glycinebetaine in the leaves of cotton. There was no evidence of any degradation of glycinebetaine in the leaves of cotton under optimal, saline or nitrogen deficient treatments, and translocation of glycinebetaine was found to be minuscule under the same treatments. De novo synthesis was the main factor that determines glycinebetaine accumulation in plants. Salinity stress results in increased synthesis and nitrogen deficiency limited synthesis, more so in old leaves of the plant. Under optimal, saline or nitrogen deficient treatments, the young leaves of cotton accumulated more glycinebetaine than the old leaves. A fast and effective technique to quantify glycinebetaine was developed by modifying the apparatus and conditions of the reinecke salt precipitation method. This technique was developed in order to quantify glycinebetaine in up to 96 samples in one assay run.