Dissecting Succulence: Crassulacean Acid Metabolism and Hydraulic Capacitance are Independent Adaptations in Clusia Leaves

Leverett, A.; Hartzell, S.; Winter, K.; Garcia, M.; Aranda, J.; Virgo, A.; Smith, A. J.; Focht, P.; Rasmussen-Arda, A.; Willats, W. G. T.; Cowan-Turner, D.; Borland, A. M.

doi:10.1101/2022.03.30.486278

bioRxiv · 10.1101/2022.03.30.486278

Dissecting Succulence: Crassulacean Acid Metabolism and Hydraulic Capacitance are Independent Adaptations in Clusia Leaves

Leverett, A.·Hartzell, S.·Winter, K.·Garcia, M.·Aranda, J.·Virgo, A.·Smith, A. J.·Focht, P.·Rasmussen-Arda, A.·Willats, W. G. T.·Cowan-Turner, D.·Borland, A. M.

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Abstract

O_LISucculence is found across the world as an adaptation to water-limited niches. The fleshy organs of succulent plants develop via enlarged photosynthetic chlorenchyma and/or achlorophyllous water storage hydrenchyma cells. The precise mechanism by which anatomical traits contribute to drought tolerance is unclear, as the effect of succulence is multifaceted. Large cells are believed to provide space for nocturnal storage of malic acid fixed by crassulacean acid metabolism (CAM), whilst also buffering water potentials by elevating hydraulic capacitance (CFT). Furthermore, the effect of CAM and elevated CFT on growth and water conservation have not been compared, despite the assumption that these adaptations often occur together. C_LIO_LIWe assessed the relationship between succulent anatomical adaptations, CAM and CFT, across the genus Clusia. In addition, we simulated the effects of CAM and CFT on growth and water conservation during drought using the Photo3 model. C_LIO_LIWithin Clusia leaves, CAM and CFT are independent traits: CAM requires large palisade chlorenchyma cells, whereas hydrenchyma tissue governs interspecific differences in CFT. In addition, our model suggests that CAM supersedes CFT as a means to maximise CO2 assimilation and minimise transpiration during drought. C_LIO_LIOur study challenges the assumption that CAM and CFT are mutually dependent traits within succulent leaves. C_LI

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Leverett, A., Hartzell, S., Winter, K., Garcia, M., Aranda, J., Virgo, A., Smith, A. J., Focht, P., Rasmussen-Arda, A., Willats, W. G. T., Cowan-Turner, D., Borland, A. M.. 2022-04-01. Dissecting Succulence: Crassulacean Acid Metabolism and Hydraulic Capacitance are Independent Adaptations in Clusia Leaves. https://doi.org/10.1101/2022.03.30.486278

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