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

Abstract

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.