Elucidation of seasonal pigmentation patterns in the involucral leaves of Leucadendron ‘Safari Sunset’

Abstract

This study investigates seasonal pigmentation patterns found in the involucral leaves of Leucadendron ‘Safari Sunset’, with the long-term aim of colour manipulation. Treatments comprised deconed shoots and shoots in which the opening of the flower head was physically prevented. During the early reproductive phase anthocyanin, chlorophyll and carotenoid concentrations were high, resulting in an unmarketable muddy colouration of the involucral leaves of control shoots. Towards anthesis there was a gradual decrease in chlorophyll, carotenoid and anthocyanin concentrations in controls. At anthesis the flower heads had opened up, coinciding with a rapid drop in chlorophyll and carotenoid concentrations, with a concurrent peak in anthocyanins. In deconed shoots, the flower heads did not open and all pigment concentrations remained fairly constant. Shoots in which flower heads were physically kept closed flowered normally, with pigmentation patterns similar to control shoots, except that anthocyanin levels remained constant. The red colour change in ‘Safari Sunset’ is directly related to the exposure of previously unexposed involucral leaf surfaces to high irradiance as the flower head opens towards anthesis. The changes in chlorophyll and carotenoid concentrations are correlated to the phenological development of the inflorescence, as changes occur irrespective of flower head opening, as long as inflorescence development continues to anthesis.