Crassulacean Acid Metabolism in the Gesneriaceae

Comparative anatomy of the vegetative organs in Pleiochiton A. Gray (Melastomataceae), with emphasis on adaptations to epiphytism

“…Succulent leaves, similar to those found in this study, occur also in several species of Peperomia and Gesneriaceae (Guralnick et al, 1986;Takemori, 2002) and are a good example of evolutionary convergence. The occurrence of a peculiar character (like the internal leaf structure) within species from different families and orders that live under similar environmental conditions is regarded as the main evidence that this resulted from natural selection (Givnish, 1988).…”

“…The occurrence of a peculiar character (like the internal leaf structure) within species from different families and orders that live under similar environmental conditions is regarded as the main evidence that this resulted from natural selection (Givnish, 1988). Specifically in the above-cited groups, the succulent tissue in the adaxial surface has its origin in periclinal divisions in cells of the protodermis; thus this tissue can be regarded as a multiseriate epidermis (Guralnick et al, 1986;Kaul, 1977;Takemori, 2002). Nevertheless, the same kind of tissue has been called hypodermis when occurring in Melastomataceae (Mentink and Baas, 1992;Metcalfe and Chalk, 1950;Reis et al, 2005).…”

“…CAM plants usually exhibit increased cell size and leaf thickness, as well as a reduction of intercellular spaces (Nelson et al, 2005). The proportion of the leaf occupied by the mesophyll in Gesneriaceae ranges from 60% to 80% in non-CAM species but decreases to 56.4% in an epiphytic CAM species (Guralnick et al, 1986). The same authors mention that anatomical characters of the leaves alone are not sufficient to indicate that certain species are performing CAM.…”

Stem CAM in arborescent succulents

“…This has the features of CAM cycling, where stomata are kept closed in the night but respiratory CO 2 is re-fixed via phosphoenolpyruvate carboxylase (PEPC) and stored in the form of organic acid (mainly malic acid) as it is typical for the CO 2 dark fixation of CAM, and organic acid decarboxylation provides CO 2 as a substrate for assimilation in the subsequent day (Rayder and Ting 1981;Diaz and Medina 1984;Nobel and Hartsock 1987;Edwards and Diaz 2006). Such CAM-cycling has been suggested to be an initial step in the evolution of full CAM (Guralnick et al 1986;Guralnick and Jackson 2001), where stomata are open during the night and CO 2 is fixed by PEPC and stored in the form of organic acid in the cell vacuoles, and where the organic acid is remobilized again, decarboxylated and the CO 2 regained fixed via ribulosebisophosphate carboxylase/oxygenase (RubisCO) behind closed stomata in the subsequent day. However, among the 17 species of Pereskia only one, i.e.…”

Changes in the plastid ultrastructure duringSedum rotundifolium leaf development

“…Such plants are usually well adapted to survival under drought. Although they generally live in habitats where they must withstand diurnal and seasonal periods of alternating wet and very dry conditions (Gibson, 1982;Smirnoff, 1996), not all CAM species are found in arid environments; in fact, many, such as the Sedum rotundifolium examined in this study, occur in the xeric microenvironments of mesic regions (Guralnick et al, 1986;Smirnoff, 1996). 5. rotundifolium, which shows daily acid fluctuations (data not shown), grows on rocky surfaces or in very thin soil in the mesic environment of Mt.…”