Fig. 4.

(A) Young's elastic modulus measured in bending plotted against the percentage contribution of the wood cylinder to the total cross-sectional area of each tested stem. Generally, in all growth forms, the modulus increases with increasing proportion of wood surface area, except for a group of older climbing stems between 38 % and 56 % contribution which have relatively low wood contributions coupled with low modulus values. (B) Young's elastic modulus measured in bending plotted against the percentage contribution of the cortex to the total cross-sectional area of each stem tested. There is a general decrease in modulus with increasing proportion of cortical tissues. (C) Young's elastic modulus measured in bending plotted against the percentage contribution of the wood to the total second moment of area of each tested stem. In general, stems increase in stiffness with increasing contribution of the wood to second moment of area (I). Interestingly, for a given value of percentage wood contribution to I, the stiffest stems [the upper cloud of points increasing in stiffness (E) towards the right] belong mostly to young climbing stems (<10 mm in diameter) that are lightly attached to vertical supports.