Skip to main content
PMC home page
Plant Physiology logoLink to Plant Physiology
. 1987 Oct;85(2):481–486. doi: 10.1104/pp.85.2.481

Physiological Changes in Portulacaria afra (L.) Jacq. during a Summer Drought and Rewatering 1

Lonnie J Guralnick 1,2, Irwin P Ting 1
PMCID: PMC1054282  PMID: 16665724

Abstract

The changes of titratable acidity, enzyme activity, water status, and pigment composition were studied in Portulacaria afra (L.) Jacq. during a normal summer drought and rewatering. Two groups of plants were grown outside under a clear plastic canopy with water stress initiated at 2-week intervals in May 1986. Drought resulted in a linear decrease of fresh weight for 80 days and there was no further fresh weight change for the next 65 days. Nocturnal CO2 uptake remained measurable for 83 days. Cessation of exogenous CO2 uptake corresponded to the point where the pressure potential (Ψp) became zero. Ribulose-1, 5-bisphosphate (RuBP) and phosphoenolpyruvate carboxylase were reduced to 50% of this activity by the end of the drought period. Phosphoenolpyruvate carboxykinase activity was undetectable after 120 to 140 days of drought. Chlorophyll (Chl) levels decreased with a preferential loss of Chl a over Chl b. Carotenoid content was relatively constant over the course of the drought period. After 145 days of drought, plants responded to rewatering within 24 hours; Ψp became positive and daytime CO2 uptake resumed after 24 hours. After 3 days, RuBP carboxylase activity reached control levels. Activity of the CAM pathway recovered after 5 days, as noted by increased diurnal acid fluctuations. Phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase activity fully recovered within 6 days. Chl levels were greater than control levels within 5 days. Chl a/b ratios took 27 days to return to control levels. The results indicated that P. afra can withstand a normal summer drought by utilizing the CAM and CAM-idling pathway for 130 to 140 days. The plants respond rapidly to rewatering because of the conservation of enzyme activity and the quick recovery of Ψp.

Full text

PDF
486

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Dittrich P., Campbell W. H., Black C. C. Phosphoenolpyruvate carboxykinase in plants exhibiting crassulacean Acid metabolism. Plant Physiol. 1973 Oct;52(4):357–361. doi: 10.1104/pp.52.4.357. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Guralnick L. J., Rorabaugh P. A., Hanscom Z. Seasonal Shifts of Photosynthesis in Portulacaria afra (L.) Jacq. Plant Physiol. 1984 Nov;76(3):643–646. doi: 10.1104/pp.76.3.643. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. 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]
  4. Harten J. B., Eickmeier W. G. Enzyme Dynamics of the Resurrection Plant Selaginella lepidophylla (Hook. & Grev.) Spring during Rehydration. Plant Physiol. 1986 Sep;82(1):61–64. doi: 10.1104/pp.82.1.61. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Holthe P. A., Szarek S. R. Physiological potential for survival of propagules of crassulacean Acid metabolism species. Plant Physiol. 1985 Sep;79(1):219–224. doi: 10.1104/pp.79.1.219. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Leegood R. C., ap Rees T. Phosphoenolpyruvate carboxykinase and gluconeogenesis in cotyledons of Cucurbita pepo. Biochim Biophys Acta. 1978 May 11;524(1):207–218. doi: 10.1016/0005-2744(78)90119-5. [DOI] [PubMed] [Google Scholar]
  7. Lorimer G. H., Badger M. R., Andrews T. J. D-Ribulose-1,5-bisphosphate carboxylase-oxygenase. Improved methods for the activation and assay of catalytic activities. Anal Biochem. 1977 Mar;78(1):66–75. doi: 10.1016/0003-2697(77)90009-4. [DOI] [PubMed] [Google Scholar]
  8. Rayder L., Ting I. P. Shifts in the Carbon Metabolism of Xerosicyos danguyi H. Humb. (Cucurbitaceae) Brought About by Water Stress : II. Enzymology. Plant Physiol. 1983 Jul;72(3):611–615. doi: 10.1104/pp.72.3.611. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Szarek S. R., Johnson H. B., Ting I. P. Drought Adaptation in Opuntia basilaris: Significance of Recycling Carbon through Crassulacean Acid Metabolism. Plant Physiol. 1973 Dec;52(6):539–541. doi: 10.1104/pp.52.6.539. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Terri J. A., Turner M., Gurevitch J. The Response of Leaf Water Potential and Crassulacean Acid Metabolism to Prolonged Drought in Sedum rubrotinctum. Plant Physiol. 1986 Jun;81(2):678–680. doi: 10.1104/pp.81.2.678. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Plant Physiology are provided here courtesy of Oxford University Press

RESOURCES