Stomatal resistance during senescence of hardwood leaves

摘要

Leaf resistance to vapor flow was measured with a diffusion porometer on hardwood trees in central New Hampshire during autumn senescence and was compared with leaf color and chlorophyll content. Daytime diffusion resistance remained at the low values found in summer (1–10 sec/cm) as long as the leaves remained green. Resistances ranged from 5 to>35 sec/cm when chlorophyll content was below 0.4 mg/g of fresh weight and leaf color was yellow green or yellow. Autumn transpiration evidently continues unabated in green leaves but declines to small values when leaves turn colo