Abstract Detail

Physiology

Suissa, Jacob [1], Green, Walton [2].

Low atmospheric CO2 levels induce nocturnal carbon accumulation in the lycophyte genus Isoëtes.

Crassulacean Acid Metabolism (CAM) is an adaptation to increase water use efficiency in dry environments. Oddly, similar biochemical patterns occur in the submerged aquatic lycophyte genus Isoëtes. It has long been assumed that CAM-like nocturnal carbon accumulation in aquatic plants is an adaptation to low daytime carbon levels in the lakes and streams they inhabit, but this has never been directly tested. To test this hypothesis, populations of Isoëtes engelmannii and I. tuckermanii were grown terrestrially in climate-controlled chambers and starved of atmospheric CO2 during the day while pH was measured for 24-hours. We demonstrate that terrestrial plants exposed to low atmospheric CO2 display diel acidity cycles similar to those in both xerophytic CAM plants and submerged Isoëtes. These results substantiate the hypothesis that carbon starvation induces nocturnal carbon accumulation in Isoëtes. Furthermore, while aquatic carbon levels undoubtedly are important in nocturnal carbon accumulation in extant Isoëtes, the induction of this behavior in terrestrial plants may suggest an earlier terrestrial evolution of this metabolism in Isoetalean ancestors in response to low atmospheric CO2 levels. We both provide support for a long-standing assumption about nocturnal carbon accumulation Isoëtes, as well as raise questions about an alternative hypothesis on the early evolution of CAM-like nocturnal carbon accumulation in Isoëtes that requires further investigation.

1 - Harvard University, Department of Organismic and Evolutionary Biology, 26 Oxford st., Cambridge, MA, 02138, United States
2 - Department Of Organismic And Evolutionary Biology, Botanical Museum 52A, 26 Oxford St., Cambridge, MA, 02138, United States

Keywords:
CAM
Isoëtes
lycophyte
plant physiology.

Presentation Type: Oral Paper
Session: PHYS1, Physiology I
Location: Virtual/Virtual
Date: Tuesday, July 28th, 2020
Time: 1:00 PM
Number: PHYS1001
Abstract ID:464
Candidate for Awards:None