Does the C4 plant Trianthema portulacastrum (Aizoaceae) exhibit weakly expressed crassulacean acid metabolism (CAM)?

Winter, Klaus, Garcia, Milton, Virgo, Aurelio, and Holtum, Joseph A.M. (2020) Does the C4 plant Trianthema portulacastrum (Aizoaceae) exhibit weakly expressed crassulacean acid metabolism (CAM)? Functional Plant Biology, 48 (7). pp. 655-665.

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Abstract

We examined whether crassulacean acid metabolism (CAM) is present in Trianthema portulacastrum L. (Aizoaceae), a pantropical, salt-tolerant C 4 annual herb with atriplicoid-type Kranz anatomy in leaves but not in stems. The leaves of T. portulacastrum are slightly succulent and the stems are fleshy, similar to some species of Portulaca, the only genus known in which C 4 and CAM co-occur. Low- level nocturnal acidification typical of weakly expressed, predominantly constitutive CAM was measured in plants grown for their entire life-cycle in an outdoor raised garden box. Acidification was greater in stems than in leaves. Plants showed net CO 2 uptake only during the light irrespective of soil water availability. However, nocturnal traces of CO 2 exchange exhibited curved kinetics of reduced CO 2 loss during the middle of the night consistent with low-level CAM. Trianthema becomes the second genus of vascular land plants in which C 4 and features of CAM have been demonstrated to co-occur in the same plant and the first C 4 plant with CAM-type acidification described for the Aizoaceae. Traditionally the stems of herbs are not sampled in screening studies. Small herbs with mildly succulent leaves and fleshy stems might be a numerically significant component of CAM biodiversity.

Item ID: 79167
Item Type: Article (Research - C1)
ISSN: 1445-4416
Keywords: CAM evolution, CO 2 assimilation, C4 photosynthesis, facultative CAM, Kranz anatomy, Sesuvioideae, stem photosynthesis, Trianthema portulacastrum.
Copyright Information: © CSIRO 2020 Open Access CC BY-NC-ND
Funders: Smithsonian Tropical Research Institute (STRI), Australian Research Council (ARC)
Projects and Grants: ARC DP160100098
Date Deposited: 03 Jul 2023 22:01
FoR Codes: 31 BIOLOGICAL SCIENCES > 3108 Plant biology > 310806 Plant physiology @ 100%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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