THE EFFECT OF INCREASING ELEVATION ON LEAF CUTICLE THICKNESS AND CUTICULAR TRANSPIRATION IN BALSAM FIR

First-year needles and stems of A. balsamea were collected at the end of the growing season along an elevational gradient on Mt. Moosilauke New Hampshire, [USA]. Tissue was sampled from the base (732 m), midslope (1143 m), forest limit (1402 m) and tree line (1455 m). Mean cuticle thickness on the adaxial needle surface decreased with increasing elevation from 3.01 to 2.21 .mu.m. A similar decline was observed for the cutinized cell wall at the lower three elevations. Associated with the decline in cuticular thickness was a 59.3% increase in the rate of cuticular water loss per gram dry weight from 732 to 1402 m. The amount of epicuticular wax and other features of leaf anatomy were also examined along the elevational gradient. The high rates of cuticular water loss in these subalpine trees increase the risk of desiccation damage at high elevations and support the concept that they can be a contributing factor in the formation of alpine tree line.