M.Sc. / Please refer to full text to view abstract

M.Sc. (Botany) / Please refer to full text to view abstract

A known method for the preservation of green foliage was adapted in order to preserve floral tissues, retaining the colour and texture, thereby providing a method suitable for the preservation of whole flowers. Initially, the effects of the existing foliage preservation process on floral tissues were studied and the resulting problems of limp sticky petals and colour loss were identified. Subsequently, with a knowledge of basic plant anatomy and of the properties of the main floral pigments, the anthocyanins, a series of experiments on petals and whole flowers were carried out in an attempt to rectify these problems and to incorporate the remedies into a method for preserving whole flowers. The problem of improving the texture and firmness of flower heads was tackled by investigating the effects of adding bulking or setting ingredients to the process fluid and establishing their optimum concentrations. In the case of flower colour, the addition of acid was required in order to maintain the bright anthocyanin colours and a range of acids was investigated. Furthermore, since it is known that in nature the anthocyanin pigments are stabilised by metal ions and copigments, the use of these agents in the preservation process was also considered. This empirical work was then validated by confirming the identity of the main pigments involved and by studying various aspects of the new preservation process. Factors examined included acid concentration, temperature, solvent composition and the addition of metal ions and copigments to solutions of petal extracts containing anthocyanin pigments. Physical changes resulting from processing, including process fluid content and the moisture absorption properties of processed petals were also measured. Finally, the application of a selection of coating materials was assessed in an attempt to increase the life span of the processed flowers by providing extra protection against environmental stresses.

Postharvest stem bending is one of the most detrimental factors that affect postharvest quality life of Gerbera jamesonii cutflower varieties. Stem bending is of economic importance in the cutflower industry in South Africa because it negatively affects the overall total sales. Growers and retailers want to improve the postharvest vaselife of this crop using suitable preservatives. The aim of this study was to determine suitable preservatives and optimal vaselife conditions that could prevent or minimise postharvest stem bending of Gerbera jamesonii “Black diamond”. The variety “Black diamond was selected and treated with four different floral preservative solutions. The relationship between stem bending and absorption rate of the preservative solutions was established. The data gathered indicated that there was a significant difference to the solution absorption rate and stem bending. Stem bending differed from 0 to 38 degrees. Stems treated on control, preservative 3 and 4 recorded the highest degrees of bending, while preservative 1 and 2 recorded the lowest degrees of stem bending within 12 day period. The performance results of the preservatives and control repeated three times under the same experimental conditions showed that preservative 1 and 2 can be used to minimise postharvest stem bending of Gerbera jamesonii ‘Black diamond’ / College of Agriculture and Environmental Sciences / M. Sc. (Ornamental Horticulture)