Canadian Forest Service Publications
Effects of plant water stress on photosynthesis and survival of four conifers. 1979. Brix, H. Canadian Journal of Forest Research 9(2): 160-165.
Issued by: Pacific Forestry Centre
Catalog ID: 2002
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Seedlings of four coniferous species, Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), white spruce (Piceaglauca (Moench) Voss), and lodgepole pine (Pinuscontorta Dougl.), were grown for 4 months from germination and then exposed to soil drying. Rates of photosynthesis were measured for all species and rates of dark respiration and transpiration were measured for Douglas-fir and hemlock. In a study of survival, seedlings were exposed to various durations of soil drying and the plant water potential was determined before the plants were rewatered; seedling survival was subsequently recorded. Rates of photosynthesis declined for Douglas-fir, hemlock, spruce, and pine when the plant water potential decreased from -10.0, -10.7, -12.4, and -6.6 bars (1 bar = 100 kPa), respectively, and became zero with potentials of -53.9, -39.7, -28.6, and -22.4 bars. When grown together in the same pot and exposed to soil drought, hemlock had a consistently lower potential than Douglas-fir, and spruce had a lower potential than pine. Hemlock could survive potentials of -40 to -60 bars, whereas seedlings of the other species survived potentials to -110 bars.