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Comparative Photosynthetic and Respiratory Responses to Temperature and Light by Pseudotsuga Menziesii Var. Menziesii and Var. Glauca Seedlings
Author(s) -
Krueger Kenneth W.,
Ferrell William K.
Publication year - 1965
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1934011
Subject(s) - photosynthesis , botany , light intensity , biology , compensation point , respiration , horticulture , physics , transpiration , optics
Douglas—fir seedlings of the geographic varieties menziesii and glauca were grown from seed collection from southern Vancouver Island, B. C., and western Montana. Photosynthetic and respiratory rates were compared for a range of temperatures, light intensities, and under constant high—intensity illumination. Maximum apparent photosynthesis occurred near temperatures of 20 degrees—25 degrees C for 35— and 65—day—old seedlings. Seedlings from Vancouver Island had significantly higher rates of photosynthesis than seedlings from Montana at certain temperatures at both ages. Respiratory rates of 35—day—old seedlings from Vancouver Island were significantly higher at 20 degrees—35 degrees C than those from Montana, but at 65 days of age only at 15 degrees and 40 degrees C. Seedlings from Montana required more light to reach the compensation point at 20 degrees C, and photosynthesized less at light intensities of 200 to 1,000 ft—c than did Vancouver Islands seedlings. Saturation intensity for seedlings from both varieties was near 3,000 ft—c. After 11 hours of illumination at 10,000 ft—c, the photosynthetic rate of Vancouver Island seedlings had declined from the initial rate significantly more than had Montana seedlings. Observed differences in photosynthesis and respiration between young seedlings from these two regions often decrease as seedlings become slightly older. Comparison of two Vancouver Island and two Montana sources showed that differences between seedlings of the same geographic variety can be greater than between seedlings of the two varieties.