Maximum Vessel Diameter Research Articles

A survey of vessel dimensions in stems of tropical lianas and other growth forms.

Vessel dimensions (total diameter and length) were determined in tropical and subtropical plants of different growth forms with an emphasis upon lianas (woody vines). The paint infusion and compressed air methods were used on 38 species from 26 genera and 16 families in the most extensive survey of vessel length made to date. Within most stems there was a skewed frequency distribution of vessel lengths and diameter, with many short and narrow vessels and few long and wide ones. The longest vessel found (7.73 m) was in a stem of the liana (woody vine) Pithecoctenium crucigerum. Mean vessel length for 33 species of lianas was 0.38 m, average maximum length was 1.45 m. There was a statistically significant inter-species correlation between maximum vessel length and maximum vessel diameter. Among liana stems and among tree+shrub stems there were statistically significant correlations between stem xylem diameter and vessel dimensions. Lianas with different adaptations for climbing (tendril climbers, twiners, scramblers) were similar in their vessel dimensions except that scramblers tended to have shorter (but not narrower) vessels. Within one genus, Bauhinia, tendril climbing species had greater maximum vessel lengths and diameters than tree and shrub species. The few long and wide vessels of lianas are thought to hydraulically compensate for their narrow stem diameters. The many narrow and short vessels, which are present in the same liana stems, may provide a high resistance auxiliary transport system.

TECHNIQUES FOR MEASURING VESSEL LENGTHS AND DIAMETERS IN STEMS OF WOODY PLANTS

Results were compared between the latex paint and compressed air methods for determining total vessel lengths, and between the sectioning and maceration methods for determining vessel diameters. The minimum, mean, median, and maximum vessel diameters were less with the sectioning method than with the maceration technique. Vessel diameter distributions were always nonnormal and had roughly similar patterns with the two techniques, but were statistically different from one another. In all six species where the paint and air methods for determining vessel length were compared, both methods showed a similar skewed vessel length distribution, with many short vessels and few long ones. Although there was no consistent pattern to the difference in results with these two methods, the vessel length frequency distributions were statistically different from one another. With the paint method, many vessels, especially many of the narrowest ones, were not paint‐filled at the paint infusion port. The air method utilized the paint method, in part, and, in addition, is based upon the incorrect assumption that all vessels in the stem are the same diameter. Both techniques tended to exclude vessel lengths of the narrowest vessels. However, the narrow vessels, although numerous, contributed an insignificant amount to the total theoretical hydraulic conductance in stems.

Techniques for Measuring Vessel Lengths and Diameters in Stems of Woody Plants

Results were compared between the latex paint and compressed air methods for determining total vessel lengths, and between the sectioning and maceration methods for determining vessel diameters. The minimum, mean, median, and maximum vessel diameters were less with the sectioning method than with the maceration technique. Vessel diameter distributions were always nonnormal and had roughly similar patterns with the two techniques, but were statistically different from one another. In all six species where the paint and air methods for determining vessel length were compared, both methods showed a similar skewed vessel length distribution, with many short vessels and few long ones. Although there was no consistent pattern to the difference in results with these two methods, the vessel length frequency distributions were statistically different from one another. With the paint method, many vessels, especially many of the narrowest ones, were not paint-filled at the paint infusion port. The air method utilized the paint method, in part, and, in addition, is based upon the incorrect assumption that all vessels in the stem are the same diameter. Both techniques tended to exclude vessel lengths of the narrowest vessels. However, the narrow vessels, although numerous, contributed an insignificant amount to the total theoretical hydraulic conductance in stems.

Tumor microvasculature following fractionated x irradiation.

The microvasculature of C3H/Bi mouse mammary carcinomas 8 mm in average diameter was evaluated using morphometric methods following six consecutive daily exposures of 500 R of x radiation. Tumor volume did not change significantly during the intervals between treatments. Tumors began to grow again 72 hours after the sixth 550-R fraction, with mean vessel length and surface area reaching maximum values and vessel diameters and volumes becoming minimal at this time. These changes were attributed to improved colloidal-carbon filling of previously existing nonfunctional vessles. When anatomically derived estimates of vascular dimensions were related to a metabolically useful blood supply, improved capability for exchange of essential nutrients occurred 72 hours after the sixth 500-R fraction.

Maximum effective vessel diameters of hardwoods

Measurements of the gas pressure required to displace water and allow gas bubbles to start continuously passing through the void structure of hardwood cross sections varying in thickness from 0.1 ... 10.0 cm have been used to calculate the maximum effective opening diameters. These diameters decrease with an increase in the thickness of the cross sections, as is the case for softwoods. Extrapolation of diameter—thickness plots to zero thickness gives the maximum vessel diameters, which agree well with microscopically determined values. The relatively small decrease in the maximum effective opening diameters with increasing thickness of the cross sections for most of the sapwood samples tested is due to irregularities in the vessel diameters and presence of perforation plates at the ends of the vessel segments. The decrease in the maximum effective opening diameter with an increase in the thickness of the cross sections is greater for the heartwood than for the sapwood. The ratio of the sapwood to the heartwood values tends to become constant between cross section thicknesses of 2.5 and 5.0 cm. This ratio was small for tyloses free northern red oak but appreciable for the hardwoods containing tyloses in the heartwood. Air drying followed by oven drying and resaturating of the specimens with water caused only small variable changes in the maximum effective opening diameters that were within the range of experimental accuracy of the measurements (approximately 5%).

The Effect of the Speed of Rotation on Segregation of Particles in a Horizontal Rotary Conical Vessel

In order to discuss the axial segregation of solid mixture in a horizontal rotary vessel, the experiments were carried out by using a horizontal conical vessel of 12.5cm inside diameter of one end, where the diameter of the vessel is a minimum, 24.5cm in i. d. of the other end, where the diameter is the maximum, and 30cm in length. As materials, three kinds of mixtures were prepared.As the result of the experiments, the larger particles of silica sand mixture having size distribution move to the point of the maximum inside diameter, and the smaller particles segregate near the end of the maximum diameter of the conical vessel at lower speed of rotation (at 20≤n<80 r.p.m.). The smaller particles migrate toward the point of smaller diameter at 80<n≤100 r.p.m., and this tendency of the segregation is contrary to the result of the segregation at n<80 r.p.m.. Most of spherical silicagel particles of the binary solid mixture which consists of spherical and irregular silica gel of nearly the same size are segregated near the end of the minimum diameter at 15≤n<80 r.p.m. and the irregular particles are collected at the point of smaller diameter at 80<n≤100 r.p.m.. The irregular particles of the binary solid mixture, whose diameter is larger than that of the spherical particles in Weigels diameter, are segregated near the end of the minimum diameter of the vessel at n=15 r.p.m.. At about 80 r.p.m., the degree of these axial segregations decreases.These experimental results are discussed on the basis of a few characteristics of cascading particles in a rotary cylinder and the shape of the conical vessel.