© 1986 Heron Publishing—Victoria, Canada
Evidence of competition for photosynthates between growth processes and oleoresin synthesis in Pinus taeda L.
Peter L. Lorio, Jr. and Robert A. Sommers
USDA, Forest Service, Southern Forest Experimental Station, 2500 Shreveport Highway, Pineville, LA 71360, USA /
Summary
A group of 10 pines (Pinus taeda L.) in a 35-year-old stand in Central Louisiana was sampled periodically from March through December 1984 for oleoresin flow
from small wounds. Oleoresin yield was closely associated with periods of calculated moderate soil water deficit and presumed
growth reduction. The period of maximum oleoresin flow coincided with the period of calculated maximum soil water depletion.
Calculated potential evapotranspiration reached a maximum in late June, but water deficits did not reach maximum levels until
September. Apparently, moderate seasonal water deficits that limit growth, but do not limit photosynthesis and translocation
of photosynthates, favor differentiation processes, such as oleoresin synthesis. Because oleoresin is a primary defense against
southern pine beetle (Dendroctonus frontalis Zimm.) attack in pines, recognition of these relationships should contribute to an understanding of southern pine beetle–host
tree interactions.
