
TY  - JOUR
A1  - Slayter, RO 
T1  - Altitudinal Variation in the Photosynthetic Characteristics of Snow Gum, <I>Eucalyptus pauciflora</I> Sieb. ex Spreng. IV. Temperature Response of Four Populations Grown at Different Temperatures
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1977
VL  - 4
IS  - 4
SP  - 583
EP  - 594
KW  - 
UR  - https://doi.org/10.1071/PP9770583 
N2  - Photosynthetic temperature response curves were measured at leaf temperatures from 10 to 40&#176;C on seedlings of E. pauciflora grown from seed collected at tree-line (elevation 1905 m) in the Snowy Mountains area and at three lower elevations, 915, 1215 and 1645 m, which correspond to those used in an earlier field study (Slatyer and Morrow 1977). The material was grown in naturally lit, temperature-controlled greenhouses at day/night temperatures of 8/4, 15/10, 21/16, 27/22 and 33/28&#176;C.   Comprehensive measurements were made on the tree-line population, in which peak rates of net photosynthesis, Pamb, reached 75 ng cm-2 s-1 at a temperature of 20°&#176;C, from material grown at 21/16&#176;. Minimum levels of intracellular resistance, rt, were 2.8 s cm-1, and of leaf gas-phase resistance to CO2 transfer, r1, were 3.2 s cm-1. Changes in rt and r1, with measurement temperature, appeared to be of approximately equal importance in mediating the overall photosynthetic temperature response. Changes in the CO2 compensation point, &#915; were of increasing importance at higher measurement temperatures.   The photosynthetic temperature optimum was markedly affected by the growth temperature regime. In the tree-line population, it increased from about 16&#176; when grown at 8/4&#176; to 24&#176; when grown at 33/28&#176;. The relationship between the observed photosynthetic temperature optimum and the day temperature of the growth regime indicated a preferred temperature for photosynthesis of 20.0&#176;, and a tendency for the temperature optimum to shift by 0.34&#176; per degree shift in the day growth temperature.   A similar effect of growth temperature on the photosynthetic temperature optimum was noted in the three lower-elevation populations, in which preferred temperatures of 21.5, 24.2 and 27.2&#176; were calculated for the material collected at 1645, 1215 and 915 m respectively. These temperatures were several degrees higher than the field-observed temperature optima, although the gradient of preferred temperature with elevation was comparable to that noted in the field study. 
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