Studies of the vegetative development of Protea cv. Sylvia and Cardinal

[摘要] ENGLISH SUMMARY: The high establishment cost of growing proteas under intensive cultivation hasnecessitated young plant management to attain an economically viable crop as soon aspossible 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 thevegetative complexity of the plants during the first growing season. During the secondgrowing season, one-year-old plants of Protea cv. Sylvia were pruned in early spring, andthe resultant regrowth thinned to between three and six shoots per bearer or leftunthinned. 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 shootsforming while not pinching the spring flush, but topping after the summer flush resultedin an average of 6.82 shoots forming by late summer. Pinching both the spring andsummer flushes resulted in an average of 8.84 shoots per plant. One-year-old Sylviaplants, pruned in early spring, produced an average of 5.5 shoots per bearer. Where allthe 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 5shoots per bearer, did not result in longer shoots or a higher percentage of floweringshoots 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 growthflush over a period of one growing season. The dry mass of leaves and stems of eachflush was measured separately and a sample analysed for total sugars and starchconcentrations. 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 increasedsignificantly during the formation of the second summer flush and the autumn flush. Theconcentration of carbohydrates (total sugars and starch combined) in the leaves and stemsof the whole shoot, increased significantly from one flush to the next, up to and includingthe 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 concentrationremained 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 plantparts of Protea cv. Sylvia were measured at two sampling dates. Plants were grown fortwo years in 101 bags in a nursery. During July and September, whole plants weresampled, dissected into leaves, shoots, stem (trunk) and roots and laboratory analysed fordry mass, starch and sugars. The two sampling dates corresponded to the end of activevegetative shoot growth in early winter and its resumption in spring. In all plant partsmonitored, 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 ofthe total plant at both sampling dates. Significant increases in the concentration andtissue content of total sugars were noted in the leaves, shoots and roots between the firstand second sampling dates. In the case of starch a significant increase in concentrationand tissue content was noted in the leaves and a decrease in the stem.

[发布机构] Stellenbosch University