INTERLOCKED GRAIN, CAMBIAL DOMAINS, ENDOGENOUS RHYTHMS, AND TIME RELATIONS, WITH EMPHASIS ON NYSSA SYLVATICA

Abstract

Interlocked grain in wood of Nyssa sylvatica Marsh. is a lapse‐time record of cyclical changes in inclination (rightward or leftward) of fusiform initial cells in the cambium. Typically the inclination cycles have periods of a decade or more. Such cycles can be interpreted as manifestations of long‐term endogenous rhythms. Interlocked grain in N. sylvatica is not the result of whole‐stem spiral grain that reverses periodically. As wavy grain in other species is a record of wavelike migration of orientational domains along the cambium, interlocked grain in N. sylvatica can be interpreted as being related to a more complex system of domains having long axial dimensions. These domains migrate or change their efficacy and directional sense in place in such a way that some regularity of inclination cycles is maintained at the various stem levels. Inclination cycle lengths have a closer relation to calendar time than they do to the amount of radial growth of the stem. This is affirmed by data from paired stems of similar ages but which grew in diameter at widely different rates.