Evidence of competition for photosynthates between growth processes and oleoresin synthesis in Pinus taeda L.

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.