Tocopherol composition in flower organs of Lilium and its variations during natural and artificial senescence

Abstract

Although the biosynthesis and function of tocopherols (vitamin E) in leaves and seeds have been studied in detail, their occurrence within other plant organs/tissues is still poorly understood. In an attempt to better understand the occurrence and possible functions of tocopherols in flowers, we measured the concentrations of the four tocopherol homologues in floral organs of Lilium (including the gynoecium, androecium, and inner and outer tepals), and evaluated their variations in tepals of cut, senescing flowers (artificial senescence) compared to controls (natural senescence). Results showed that flowers accumulated α-tocopherol at significant amounts, while γ-tocopherol was present at much lower concentrations. The androecium was the organ showing the highest amounts of tocopherols, with a specific accumulation in the pollen, while tocopherols were not present in the gynoecium. Inner and outer tepals also contained significant amounts of α- and γ-tocopherol, whose levels increased during senescence. α-Tocopherol increased in both outer and inner tepals earlier and to a higher extent during senescence of cut flowers than in controls. The lowest concentrations of tocopherols were found at the beginning of tepal development (in green tepals), while the highest concentrations were found in chlorophyll-free, senescing tepals, especially in cut flowers. It is concluded that (i) tocopherols accumulate in outer and inner tepals, and in the androecium of Lilium flowers, particularly in the pollen, and (ii) tocopherols increase with the progression of tepal senescence, and most particularly in cut flowers, which show advanced senescence (reduced longevity).