© 1986 Heron Publishing—Victoria, Canada
Free proline changes in Pinus taeda L. callus in response to drought stress
R. J. Newton, S. Sen and J. D. Puryear
Department of Forest Science, Texas Agricultural Experiment Station, Texas A & M University System, College Station, TX 77843,
USA / Received July 4, 1986
Summary
The amino acid, proline (PRO), may have an important role in plant adaptation to drought stress. To study the effect of drought
stress on PRO content of pine tissues, we measured free PRO by high pressure liquid chromatography in control ( –0.4 MPa)
and drought-stressed ( –0.8, –1.0, –1.3,
–1.6 MPa) callus tissue of Pinus taeda L. after eight weeks of growth. Drought stress was induced by adding polyethylene glycol (PEG) to the nutrient media. The
relation between PRO accumulation and water potential was influenced by composition of the medium and temperature. Callus
growing in media with water potentials of –0.8 MPa showed no increase in PRO compared to control callus in media at –0.4 MPa.
When callus tissue was subjected to low water potentials (–1.6 MPa), endogenous PRO concentration increased 40-fold, while
callus fresh weight decreased by more than 90%. When exogenous PRO was added to the nutrient media, endogenous PRO was directly
proportional to the exogenous PRO concentration rather than reduction in callus growth.
Thus low water potential in callus results in endogenous PRO accumulation and large reductions in callus fresh weight growth.
Proline accumulation in pine cells appears to be related to mechanisms associated with tolerance to desiccation.
