Leaf demography, bud germination, establishment and root growth of sugarcane

Investigates various aspects of the growth of sugarcane (Saccharum officinarum L.). Compares the use of traditional methods of growth analysis with the more recent demographic approaches. Through this comparison, the efficacy of demography as a more effective tool for the assessment of growth in clonal systems such as sugarcane would be determined. Both approaches were used to compare growth responses to varying levels of fertiliser, two herbicide treatments and the application of compost in three separate agronomic experiments. The classical and demographic approaches to plant growth analysis were found not to be comparable as techniques for measuring the responses of plants to their environment. Leaf demography indicated physiological attributes of the crop in relation to survival, that could not have been revealed by the traditional approach. The two approaches were complementary. The belief that younger buds, from the top of sugarcane stems, germinate faster than older buds was tested by an in depth study of germination and establishment, in relation to bud position along the length of a stem, using a diversity of clones. Bud age/germination time relationships were more prevalent in clones of S. officinarum and it appears that this trait may be characteristic of, and inherited from, this species. It was discovered that sugarcane plants of the same clone, which germinate late, had the ability to catch up in growth in terms of leaf production, with those which germinated earlier. The physiological status of the canes and their effect on bud germination and environmental influences on the genetic expression of germination characteristics are also examined and discussed. Shoot and root growth are analysed, and their relationships determined, for three cultivars of sugarcane and Erianthus arundinaceus, a species that has been crossed with sugarcane and shows potential for inclusion in sugarcane breeding programmes. The root system of E. arundinaceus is more extensive and vigorous than those of the sugarcane cultivars. A full description of the growth characteristics of both roots and shoots is provided for the four cultivars studied. The inherent constraints on experimentation due to the nature of sugarcane are discussed.