RELATIONSHIP AMONG VESSEL DIAMETER,VESSEL FREQUENCY,AND SPACING OF PARENCHYMA BANDS IN WOOD OF CARYA TOMENTOSA NUTT., MOCKERNUT HICKORY

Vessel-lumen diameter, vessel frequency, and spacing of concentric, tangential bands of parenchyma cells follow well defined trends across annual growth rings of Carya tomentosa Nutt., mockernut hickory. These cross-ring cellular changes were correlated with each other to a considerable degree but not tightly linked. Vessel-lumen diameter decreased in a strongly linear fashion, as a function of distance from the inner ring boundary. Distance between tangential, concentric bands of axial wood parenchyma cells also decreased across rings, but followed a less strongly linear trend. Vessel frequency decreased abruptly after the large-pore zone and then increased to the outer ring boundary. Radial growth rate, as indicated by ring width, strongly influenced these trends. For all three cellular characteristics, the cross-ring trend was abrupt in narrow rings and more gradual in wide rings. An anomalous ring of Carya tomentosa, and three similar rings of Carya glabra (Mill.) Sweet, showed a decrease in interband distance and then an abrupt increase followed by another decrease to the outer ring boundary, whereas vessel diameter remained small and uniform after an initial decrease. The three cellular characteristics were concluded to be under separate physiological controls, although growth rate seems to exert a considerable, parallel influence on them.