Why Snowdrop ( Galanthus nivalis L.) tepals have green marks?

Abstract

Photosynthetic competence in vegetative and reproductive structures of the early-flowering Common Snowdrop ( Galanthus nivalis L.) was studied by the use of chlorophyll (Chl) fluorescence techniques as well as of oxygen exchange measurements. The white Snowdrop flower consists of three outer tepals and three shorter inner ones, which latter are chararacterized by specific green marks, commonly considered as nectar guides. All the Chl-containing organs (leaves, inner tepals, stalks, capsules) examined were photosynthetically active showing medium to high potential quantum efficiencies of photosystem II ( F v / F m : 0.64 – 0.72 ) after dark adaption. With increasing photon flux densities electron transport rates, actual quantum yields and photochemical quenching coefficients of the main photosynthetic organs decreased in the order: leaf, stalk and tepal. At moderate PFDs the inner tepals reached maximum electron transport rates, which came up to about 60% of concomitant developing leaves. Maximum net photosynthesis of the inner tepals (1.9 μmol O 2 m −2 s −1) was about one-fourth of the fully developed leaves (7 μmol O 2 m −2 s −1). Apart from their main function in attracting and guiding animal pollinators, a second relevant function is proposed for the green patterned inner tepals in performing an efficient photosynthesis and providing the flower and the developing seeds with photo-assimilates.