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Net CO 2 output by CAM plants in the light: the role of leaf conductance
Author(s) -
Frimert Volker,
Kluge Manfred,
Smith J. Andrew C.
Publication year - 1986
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1986.tb03365.x
Subject(s) - conductance , botany , stomatal conductance , chemistry , horticulture , cuticle (hair) , zoology , biology , photosynthesis , anatomy , mathematics , combinatorics
The reasons for CO 2 release by some CAM plants during the light period were investigated by comparative gas‐exchange studies with three leaf‐succulent species, Kalanchoë tubiflora Hamet, Sedum morganianum E. Walth. and Sempervivum tectorum L. Sempervivum showed net CO 2 output during the day at constant day‐night temperatures of both 15 and 25°C, whereas Kalanchoë and Sedum showed no CO 2 release at this time at either temperature. Net nocturnal CO 2 uptake was markedly reduced at 25°C compared with 15°C in Kalanchoë and Sempervivum , while CO 2 was released at night at higher temperature by Sedum if leaf/air vapour pressure difference was also increased. Values for intercellular partial pressure of CO 2 (p i CO2 ) were calculated from leaf conductance and were characteristically lowest in the dark and highest in the light period. Maximum values of p i CO2 ranged from 264 Pa in Sedum to 87 Pa in Kalanchoë , but were somewhat lower than those reported from direct measurements of the gas phase in other CAM plants. Leaf conductance declined with increasing p i CO2 in all three species. Minimum values of approximately 0.2 mmol m −2 s −1 were observed at p i CO2 = 33 Pa in Kalanchoë and Sedum , with no further decrease at higher p i CO2 , implying that this largely represented the conductance of the cuticle. In Sempervivum , however, leaf conductance declined more gradually, and was as much as 0.8 mmol m −2 s −1 at the highest observed values of p i CO2 . The cause of net CO 2 output in the light by Sempervivum thus appeared to be lower stomatal sensitivity to CO 2 , resulting in relatively high leaf conductance even at times when p i CO2 greatly exceeded that of ambient air.