Colour Change in Flowers of Lathyrus hirsutus during Senescence

Abstract

ALTHOUGH there has been some work on the nature of changes in flower colour during development1–3, little is known about changes during senescence. The anthocyanin-pigmented flowers of Lathyrus hirsutus L. exhibit as they age a well marked colour change immediately before the petals show obvious loss of turgor. The mature standard petal is bluish red and it fades through blue to greenish blue; the wing petals are pale blue and fade to greenish blue. It was suggested in earlier work that blueness in mature flowers of Lathyrus species is promoted by flavonol glycoside co-pigments3–5. Thus it was found that the blue wing petals of L. hirsutus contain greater quantities of co-pigment relative to anthocyanin than the standard petals4. In this species the pH of the expressed sap of the wings was found to be rather higher than that of the standard petal, and it was suggested that this pH difference might contribute to the bluer appearance of the wing petal.