Browsing by Author "Hettasch, Hans Bernhard"
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- ItemStudies of the vegetative development of Protea cv. Sylvia and Cardinal(Stellenbosch : Stellenbosch University, 1999-12) Hettasch, Hans Bernhard; Jacobs, G.; Theron, K. I.; Stellenbosch University. Faculty of AgriSciences. Dept. of Horticultural Science.ENGLISH SUMMARY: The high establishment cost of growing proteas under intensive cultivation has necessitated young plant management to attain an economically viable crop as soon as possible after planting. Rooted cuttings of Protea cv. Sylvia (P. eximia x P. susannae) were planted and shoots were pinched and topped at various growth stages to increase the vegetative complexity of the plants during the first growing season. During the second growing season, one-year-old plants of Protea cv. Sylvia were pruned in early spring, and the resultant regrowth thinned to between three and six shoots per bearer or left unthinned. Plants which were not pinched or topped during the first growing season, grew a single stem; pinching after the spring flush resulted in an average of 4.34 shoots forming while not pinching the spring flush, but topping after the summer flush resulted in an average of 6.82 shoots forming by late summer. Pinching both the spring and summer flushes resulted in an average of 8.84 shoots per plant. One-year-old Sylvia plants, pruned in early spring, produced an average of 5.5 shoots per bearer. Where all the shoots were left, some became dominant and the remainder became weak, spindly, non-flowering shoots. Thinning the sprouts on the bearers in the spring to 3, 4 or 5 shoots per bearer, did not result in longer shoots or a higher percentage of flowering shoots than leaving 6 shoots per bearer. Whole shoots of Protea cv. Sylvia (P. eximia x P. susannae) and Pro tea cv. Cardinal (P. eximia x P. susannae) plants were sampled at the conclusion of each successive growth flush over a period of one growing season. The dry mass of leaves and stems of each flush was measured separately and a sample analysed for total sugars and starch concentrations. Total dry mass of both stems and leaves of 'Sylvia' and 'Cardinal' remained similar during growth of the spring and first summer flushes and then increased significantly during the formation of the second summer flush and the autumn flush. The concentration of carbohydrates (total sugars and starch combined) in the leaves and stems of the whole shoot, increased significantly from one flush to the next, up to and including the second summer flush. The concentration of carbohydrates in the leaves of the whole shoot was significantly reduced after the winter, while in the stems the concentration remained similar. Total sugars and starch concentrations in the leaves of both 'Sylvia' and 'Cardinal' were significantly higher than in the stems on all flushes. The dry mass, concentration of starch and concentration of total sugars of different plant parts of Protea cv. Sylvia were measured at two sampling dates. Plants were grown for two years in 101 bags in a nursery. During July and September, whole plants were sampled, dissected into leaves, shoots, stem (trunk) and roots and laboratory analysed for dry mass, starch and sugars. The two sampling dates corresponded to the end of active vegetative shoot growth in early winter and its resumption in spring. In all plant parts monitored, dry mass did not increase significantly from one sampling date to the next. Tissue content of both total sugars and starch in the leaves represented half the amount of the total plant at both sampling dates. Significant increases in the concentration and tissue content of total sugars were noted in the leaves, shoots and roots between the first and second sampling dates. In the case of starch a significant increase in concentration and tissue content was noted in the leaves and a decrease in the stem.