Intra-specific relationship between vessel length and vessel diameter of four species with long-to-short species-average vessel lengths: further validation of the computation algorithm

Key message Within a species, vessel length is a linear function of vessel diameter; this suggests that in future, concepts about vessel size optimization need to be revised. Abstract This study extends the previous reports that vessel length is a linear function of vessel diameter. Strong relationships were revealed in the wide-vessel species known to have long average vessel lengths. The method used was to reveal the length of cut open vessels by the injection of rubber polymers mixed with ultraviolet sensitive dyes prior to injection and polymerization. Following injection and polymerization, the diameter of every vessel containing rubber was measured at different distances from the injection surface. Then, these values were divided into vessel diameter size classes; the number of vessels in each bin size was used to assess vessel length. Vessel length and diameter were measured in current year stems of Acer, Populus, Vitis, and Quercus representing short-vessel-to-long-vessel species. Our results showed that the wider vessels were also longer vessels. In addition, mean vessel diameter of rubber-injected vessels increased with distance from the injection surface. If vessel diameter changed randomly over the length of individual vessels, then the correlations in the previous two sentences would not exist.