Induction and Repression of CAM inSedum telephiumL. in Response to Photoperiod and Water Stress

Autor: H. S. J. Lee, H. Griffiths
Rok vydání: 1987
Předmět:
Zdroj: Journal of Experimental Botany. 38:834-841
ISSN: 1460-2431
0022-0957
Popis: Lee, H. S. J. and Griffiths, H. 1987. Induction and repression of CAM in Sedum telephium L. in response to photoperiod and water stress.—J. exp. Bot. 38: 834-841. The introduction and repression of CAM in Sedum telephium L., a temperate succulent, was investigated in watered, progressively draughted and rewatered plants in growth chambers. Measurements were made of water vapour and C02 exchange, titratable acidity (TA) and xylem sap tension. Effects of photoperiod were also studied. CAM was induced by drought under long or short days, although when watered no CAM activity was expressed. C3-CAM intermediate plants were used for the investigation of water supply. Those which had received water and those drought-stressed both displayed a similar nocturnal increase in TA, with a day-night maximum (AH+) of 69 ??mol g"1 fr. wt. The watered plants took up C02 at a maximum rate of 2-2 /tmol m 2 s-1 only in the light period, while the draughted plants showed a maximum nocturnal C02 uptake rate of 0-69 /rmol m~2 s Subsequently, as CAM was repressed, the watered S. telephium displayed little variation in TA, with constant levels at 42 /jmol g"1 fr. wt. (day 10). After 10 d of drought stress, the CAM characteristics of S. telephium were also affected, with reduced net C02 uptake and AH+. The transition between C3 and CAM in S. telephium can be described as a progression in terms of the proportion of respiratory C02 which is recycled and refixed at night as malic acid, in comparison with net C02 uptake. Recycling increased from 20% (day 1) to 44% (day 10) as a result of the drought stress and was high in both the CAM-C3 stage (no net C02 uptake at night) and also in the drought-stressed CAM stage (reduced net C02 uptake at night). The complete C3-CAM transition occurred in less than 8 d, and the stages could be characterized by xylem sap tension measurements: CAM = 0-50 MPa; C3-CAM = 0-36 MPa; C3 = 0-29 MPa. Key words—CAM, Sedum telephium L., recycling. Correspondence to: Department of Plant Biology, The University, Newcastle-upon-Tyne NE1 7RU, U.K.
Databáze: OpenAIRE
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