CAM has been found in nine succulent species of Peperomia, a genus of the Piperaceae which, therefore, represents a new family having CAM. The amplitude of the daily fluctuation in malate content as well as a complex of xeromorphic characters of the nine succulent species of Peperomia have been compared. The congenital foliar folding, which results in subunifacial leaves, has been found to be ineffective in reducing the surface/volume ratio, and therefore it has no overall importance for adaptation to xeric conditions. The degree of CAM expression is correlated with the site of the photo¬synthetizing cells ; nevertheless, P. congesta Kunth with relatively small green cell exhibits high daily fluctuation in malate content, while P. flexicaulis Heinsich with big green cells shows low malate fluctuation. High values of « mesophyll succulence » typical of CAM plants have been found in P. congesta and in P. sp. affinis nivalis. CAM activity appears to be less effective under long-day conditions and high night temperature in most of the studied Peperomia. Species of Peperomia from more xeric environments, as P. columella Rauh & Hutchison, P. congesta. P. sp. affinis nivalis, show high CAM activity associated with a high degree of xero¬morphism, but less xeromorphic species, as P. sp. 20230 and P. dolabri¬formis Kunth also show high malate fluctuation.
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