Br. Roberts et Wn. Cannon, GROWTH AND WATER RELATIONSHIPS OF RED SPRUCE SEEDLINGS EXPOSED TO ATMOSPHERIC DEPOSITION AND DROUGHT, Canadian journal of forest research, 22(2), 1992, pp. 193-197
Two-year-old containerized seedlings of red spruce (Picea rubens Sarg.
) were subjected to ozone (O3) fumigation (0.25 ppm), simulated acid r
ain (pH 4.2 or 3.0), and drought prior to measurement of changes in gr
owth and plant water status. Drought caused a significant decline in t
erminal height growth and new-shoot dry weight, but old-shoot dry weig
ht, root dry weight, and root/shoot ratio were not appreciably affecte
d. Deposition treatment (O3 and (or) acid rain) influenced both shoot
and root dry weight but did not significantly affect height or root/sh
oot ratio. Treatment with either 0.25 ppm O3 alone or pH 3.0 rainfall
alone caused the greatest reduction in growth, while treatment with 0.
25 ppm O3 + pH 4.2 rain had the least effect. The influence of deposit
ion treatment generally was more pronounced in seedlings subjected to
drought than in well-watered plants. Seedlings subjected to drought ha
d lower (more negative) water potentials than well-watered plants rega
rdless of deposition treatment. While there were no significant differ
ences in the water status of well-watered seedlings exposed to various
deposition treatments, xylem water potential and osmotic potential of
drought-stressed seedlings treated with O3 alone were consistently lo
wer than these characteristics in seedlings treated with O3 + acid rai
n together. Except for one deposition treatment (0.25 ppm O3 + pH 3.0
rain) there was no evidence for osmotic adjustment of red spruce seedl
ings in response to stress factors imposed in this study.