Fig. 3.

The intricate covariation of plant height, tip-to-base vessel widening rate, stem tip vessel diameter, stem base vessel diameter, and number of vessels per unit leaf area. The white cylinders represent plants of different heights; the black cones within them represent vessels. In our experiment, for a given unit of leaf area, represented by the constant-sized leaf above each stem, the number of vessels decreased with increasing plant height. At the same time, terminal vessel diameter increased, represented by the wider apices of the vessels. Given tip-to-base vessel widening, the rate of which is constant over height increases, vessel diameter also becomes predictably wider at the stem base with height growth, represented by the wider bases of the vessels. This delicate synchronization of multiple factors led to a similar whole-plant conductance per leaf area as individuals become taller. (This figure is available in colour at JXB online.)