Heritability of ozone sensitivity in open-pollinated families of black cherry (Prunus serotina Ehrh.)

First-year seedlings of black cherry, representing 10 open-pollinated families from wild parents, were exposed in CSTR chambers to replicated treatments of 30, 60, 90, and 120 ppb ambient ozone for a 7 hr day^-1, 5 day wk^-1. Stem height, occurrence of leaf senescence, and visible foliar injury expressed as adaxial stipple were measured weekly during the 10 wk duration of exposure. Basal stem diameters were measured before and after fumigation. Stipple began to occur in week 1 of the 120 ppb ozone treatment, week 2 of the 90 ppb treatment, and week 4 of the 60 ppb treatment. No stipple occurred on any seedlings exposed to 30 ppb ozone. Premature leaf senescence occurred in all treatments, but sooner and more severely at higher concentrations of ozone. Relative diameter growth rates declined as ozone concentrations increased. Families differed significantly in their response to ozone treatments in severity of adaxial stipple, but not in leaf senescence or height or diameter growth. Family heritability estimates for foliar injury, calculated by treatment and week of measurement, were generally above 0.5 in the 90 and 120 ppb ozone treatments. The relative ozone sensitivity of these 10 families under CSTR conditions corresponded well with sensitivity rankings of their 27-yr-old parents, replicated in a clonal seed orchard, and growing under ambient ozone exposures. The existence of localized, heritable variation in ozone sensitivity in wild populations has obvious implications for the use of bioindicators in forest health monitoring.