BASELINE GROWTH STUDIES OF LEUCOSPERMUM 'SUCCESSION II' AND 'SOLEIL' IN CONTRASTING MEDITERRANEAN CLIMATIC AREAS

Abstract

Leucospermum exports from South Africa for the 2013/2014 season comprised 45% (number of stems) of the combined exports of Leucadendron, Leucospermum, and Protea. The determining quality parameter for Leucospermum cut flowers is stem length, with stems sold per centimetre stem length. Over production of short-stemmed Leucospermum cut flowers affect the South African fynbos market share negatively on the export market. Information on the physiology of shoot extension growth, the timing of appendage formation and factors which directly affect shoot length is limited for Leucospermum. Subsequently, shoot extension growth of Leucospermum 'Succession II' (L. lineare × L. cordifolium) and 'Soleil' (L. glabrum × L. cordifolium) was studied to establish its relationship to the timing of appendage formation in two contrasting production areas in South Africa (Hopefield, at 50 m altitude, with particularly warm dry coastal summers; Piketberg, approximately 66 km from Hopefield, but at 800 m altitude, displaying a more moderate, Mediterranean climate). For both regions, shoot extension growth was linear, following an initial lag phase. In all cases 50% or more of the final number of leaves per shoot was differentiated at ca 100 mm stem length. Stems were significantly more extended in the cooler production region of Bo-Piketberg compared to Hopefield and final stem length appears to be area dependent. This data serves as baseline to further studies which aim at evaluating the efficacy of exogenously applied plant growth regulators to increase the stem length of problematic Leucospermum cultivars in warm areas, as well as short-stemmed cultivars such as 'Jelena' produced in cooler areas, in both cases, without compromising flower quality.