THE EFFICACY OF LED LIGHTS AND GROWTH REGULATOR SPRAYS AT CONTROLLING CHILLING INJURY IN LEUCOSPERMUM POTTED PLANTS

Leucospermum cut flower stems are prone to chilling injury and leaf yellowing as a result of long-term cold storage below 4°C as is required when exporting Leucospermum by sea freight from South Africa to European markets. Potted plants of Leucospermum 'Memory' (L. cordifolium selection) and Leucospermum 'Rigoletto' (L. cordifolium × L. glabrum) were subjected to LED lighting (treatments included 'full', 'half' and 'no light' levels) and growth regulator treatments (500 mg L Promalin® and MaxCel™ respectively) to evaluate their efficacy for alleviating cold-induced injuries after a three week cold storage period. The plants subjected to a 'full light' LED treatment showed a significant reduction in chilling injury and leaf yellowing in comparison to plants subjected to the 'no light' treatment. Promalin® and MaxCel™ showed no or little ability to reduce the associated postharvest cold storage disorders. It was concluded that LED at a light energy level of 25.03 ± 2.09 μmol m s was effective at reducing leaf yellowing and chilling injury. A range of Leucospermum cultivars should also be evaluated for its suitability to be placed in cold-storage with supplemented LED lighting.