Abstract
The possibility that Crassulacean acid metabolism (CAM) is subject to long day photoperiodic control in Portulacaria afra (L.) Jacq., a facultative CAM plant, was studied. Periodic measurements of 14CO2 uptake, stomatal resistance, and titratable acidity were made on plants exposed to long and short day photoperiods. Results indicates that waterstressed P. afra had primarily nocturnal CO2 uptake, daytime stomatal closure, and a large diurnal acid fluctuation in either photoperiod. Mature leaf tissue from nonstressed plants under long days exhibited a moderate diurnal acid fluctuation and midday stomatal closure. Under short days, there was a reduced diurnal acid fluctuation in mature leaf tissue. Young leaf tissue taken from nonstressed plants did not utilize the CAM pathway under either photoperiod as indicated by daytime CO2 uptake, lack of diurnal acid fluctuation, and incomplete daytime stomatal closure.
The induction of CAM in P. afra appears to be related to the water status of the plant and the age of the leaf tissue. The photosynthetic metabolism of mature leaves may be partly under the control of water stress and of photoperiod, where CAM is favored under long days.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Gregory F. G., Spear I., Thimann K. V. The Interrelation between CO(2) Metabolism and Photoperiodism in Kalanchoë. Plant Physiol. 1954 May;29(3):220–229. doi: 10.1104/pp.29.3.220. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hanscom Z., Ting I. P. Responses of succulents to plant water stress. Plant Physiol. 1978 Mar;61(3):327–330. doi: 10.1104/pp.61.3.327. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ting I. P., Hanscom Z. Induction of Acid Metabolism in Portulacaria afra. Plant Physiol. 1977 Mar;59(3):511–514. doi: 10.1104/pp.59.3.511. [DOI] [PMC free article] [PubMed] [Google Scholar]