Constituent and Induced Tannin Accumulations in Roots of Loblolly Pines

Loblolly pine (Pinus tueda L) has become the most important source of wood fiber in the southern United States. This tree is an excellent competitor and recovers well from a variety of adverse conditions. ‘a2 The value of loblolly pine as a plantation tree has encouraged many researchers to devote their careers to the study of this species. It is surprising then that the root system of loblolly pine has received so little attention! I felt that an anatomical study of loblolly pine roots would be valuable and chose to measure tannin abundance as a primary trait to evaluate root health at the microscopic level. This histological study of tannin in pine roots follows extensive microscopy of pine cells in culture and in stem tissue begun in 1963.3 Of particular interest throughout my studies is the manner in which tannins are contained in cellular organelles until tissue death or cell membrane rupture. These tannins are nonspecifically absorbed by cell walls and organelles. These processes are easily observed in loblolly pine roots that have a high turnover rate, especially cortical cells of mycorrhizal roots. . Nutritional tests with pine callus cells indicate that cells accumulate tannin within cell membranes of the endoplasmic reticulum.@ When nutrients such as nitrogen are altered, many callus cells fill with tannin. This seems also to occur 4 in pine roots on certain sites. The hypothesis of this study was that two processes of tannin accumulation occur in root tissue. Constituent tannins accumulate in all root tissues, whereas the process controlling induced tannin is related to stress. Also, it appears that tannin has a close relationship to the deposition of cellulose and lignin in cell walls. After observing many thin sections, I focused on anatomical differences between constituent tannin accumulation in periderm cells and induced tannin in cells responding to stress. This paper describes the types of