BIOMECHANICAL ATTRIBUTES OF THE LEAVES OF PINE SPECIES

The flexural stiffness EI, elastic modulus E, second moment of area I, length L, and weight Wt of foliage leaves from 26 species of pine were measured to determine the manner in which EI is scaled to leaf size (L or Wt, or both) and to determine if the biomechanical attributes of foliage leaves could be juxtaposed with the systematic affiliations of species within Pinus Biomechamcal and morphometric data were explored based on a model from engineering theory that predicts the relationships among EI, Wt and L provided that the maximum tip-deflection δmax of an untapered cantilevered beam sustaining its own weight is maintained as the beam either increases in length or weight, or both, I e δmax = Wt L2/8EI The data show that EI disproportionately increased as either Wt or L, or both increased The allometry of leaves did not conform to that predicted by the model Rather, EI was proportional to the product of Wt and L raised to an exponent slightly greater than one Thus, Omax was predicted not to be maintained as either Wt or L, or both, increased, as verified by observations The relationship between El and Wt(L) differed for species typically producing two leaves per fascicle and those bearing more than two leaves per fascicle Also, El is geometrically constrained by the number of leaves produced per fascicle, principally in terms of the effects of the number of leaves per fascicle on I © 1991 Annals of Botany Company.