Relative sensitivity of 18 full-sib families of Pinustaeda to O3

Abstract

Seedlings of 18 full-sib families of loblolly pine (Pinustaeda L.) were screened for sensitivity to 0.10, 0.15, 0.20, or 0.25 ppm O3 in 8-h exposures. Primary needles of newly germinated seedlings and secondary needles of 1-year-old trees were exposed when the needle ages were 3–4 and 8–12 weeks, respectively. Significant variation in foliar symptom expression was noted among families, and was nearly identical for both primary and secondary needles. Family 6-13 × 2-8 was the most sensitive in eight of nine treatments, and was significantly more sensitive than the remaining 17 families in five of nine treatments. In all cases, family 6-13 × 2-8 sustained greater injury than the families involving parent tree 504 (three families) and the difference was significant in eight of nine treatments. The data suggest that it may be feasible to use sensitive and insensitive families of loblolly pine as air pollutant bioindicators, although considerable further development is necessary. The finding that sensitivity and tolerance may be heritable warrants further study.