Dear Phillip,

Leaf construction cost is measured as how much glucose is invested to fix on gram carbon ( (gram per gram CC). Leaf construction cost , in gram glucose per gram dry wt.

I am giving one formula that is given by Williams et al. (1987).

Leaf CC (g glucose g –1) was calculated using a formula based on the growth efficiency of the leaf tissue, heat of combustion and ash and nitrogen concentration of leaves according to Williams et al. (1987):

CC = [(0.06968Hc– 0.065)(1–A) +7.5kN/14.0067)]/Eg

Where, Hc is the ash free heat of combustion (kJ g–1), A is the ash concentration (g g–1), k is the oxidation state of the nitrogen source (+ 5 for nitrate or –3 for ammonium), N is the organic nitrogen concentration (g g–1) and Eg is the growth efficiency. The value used in this study for Eg was 0.89 (Williams et al., 1987).

I understand all parameters used in the formula except two absolute values which are used .I do not know what is meant for 0.06968, for what parameter this value is used. Is this an absolute value which is used in the calculation or represents some? Similarly, 0.065 is what for?

Please, any one can help me.