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- Author or Editor: W. E. Barrick x
Needle surface characteristics and NaCl penetration rates were compared and related to deicing salt spray injury for resistant Austrian pine, Pinus nigra Arnold, and susceptible Eastern white pine, Pinus strobus L. Stomata in longitudinal rows separated by parallel ridges characterized needle surfaces of both species; surface fine structure was free of trichomes or other recognizable structures. Pinus nigra in comparison to P. strobus had greater surface area (3.64 cm2/needle vs. 1.87 cm2/needle) and larger quantities of epicuticular wax 183 μg/cm2 vs. 75 μg/cm2). Thin-layer chromatography indicated no distinct differences in epicuticular wax chemistry. Surface wettability, measured by contact angle, was similar. Retention of an aqueous solution was similar when needles were attached to fascicles. Penetration of 36C1 was significantly greater in needles of P. nigra on a surface area basis (P. nigra = 9,839 dpm/cm2, P. strobus = 3,503 dpm/cm2). No differences in penetration occurred when expressed on a fresh weight basis. Electron microprobe analysis substantiated a greater penetration of Na+ and Cl- in needles of P. nigra. Levels of Na+ were higher than Cl− in both species. Triphenyl tetrazolium chloride studies indicated greater sensitivity to increasing concentrations of NaCl in needles of P. strobus and in P. nigra. Differences in species sensitivity appears to be related to protoplasmic sensitivity rather than to differences in penetration of Na+ and Cl− ions.