Spore wall cytochemistry and structure in five species of the liverwort Riccia (Ricciaceae)

Abstract

Abstract The spore wall of Riccia plano-biconvexa, R. fruchartii, R. cavernosa, R. stenophylla, and R. curtisii was analyzed using light microscopy. The study involved cytochemical analysis to distinguish the different layers of the sporoderm and assess their chemical composition. In all the species studied, the sporoderm was found to have a tri-layered exine, consisting of a lamellar exine 1 that forms ridges and depressions, an intermediate exine 2, and a thick and generally discontinuous exine 3. Cytochemical studies indicated that exine 1 and 2 are composed of sporopollenin, while exine 3 is a mixture of sporopollenin and polysaccharides. The intine, on the other hand, is the only layer that is purely cellulosic and contains pectins. Based on the chemical composition and structural organization, exine 1 and 2 can be categorized as ectexine while exine 3 corresponds to an endexine. We emphasize the importance of using cytochemical tests to study the spore wall in liverworts and other bryophytes.

Keywords

• exine
• intine
• liverwort sporoderm
• Riccia
• sporopollenin