Effect of Temperature on Photosynthesis and Respiration in Red and Loblolly Pines

Abstract

The growth of red pine (Pinus resinosa Ait.) planted in the Duke Forest has been very slow compared with the expected growth of this species within its niatural range. Seedlings which were three years old when planted attained an average height of only 2.36 feet after eight growing seasons (8).The average height of fifteen-year-old red pine saplings on medium sites in Connecticut was about 17.5 feet (7).There is no evidence of damage to the young trees by fungi nor by insects. The soil of the plot on which the planting was made is reasonably fertile as indicated by the good growth of slash pine (Pinus caribaea Morelet) and loblolly pine (Pinus taeda L.) on the immediately adjacent plots which have similar soil. The slash and loblolly pine trees were planted as one-year-old seedlings at the same time as the red pine and in eight growing seasons attained average heights of 12.6 and 18.2 feet, respectively. The supply of moisture is at least as favorable for the growth of trees at Durham as within the natural range of red pine, for the ratio of precipitation to evaporation is higher in North Carolina than in Connecticut during the summer. The maximum photoperiod in Connecticut is about forty minutes greater than that at Durham, but it seems unlikely that the photoperiod is an important factor, for it has been shown that the length of the growing season and the rate of growth of red pine at Durham were not modified by artificially prolonging the photoperiod (9). GUSTAFSON (4) reported that red pine seedlings must be subjected to freezing during the winter if they are to resume growth in the spring. Winters are always cold enough at Durham to insure adequate exposure to low temperature for breaking dormancy and careful observations have shown (9) that red pine resumes growth promptly in the spring. There is a consistent difference in temperature between the two regions, the mean summer temperature in Durham being higher by more than five degrees Centigrade. It is well known that temperature may have an important effect on growth and distribution of plants (11)

Relation Between Light Intensity and Rate of Photosynthesis of Loblolly Pine and Certain Hardwoods

“…The natural fluctuations in temperature might have considerable effect on the rate of apparent photosynthesis through changes in the rate of respiration. DECKER (3) found the apparent photosynthesis of loblolly pine to be nearly twice as high at 30°as at 40°C. and the rate of respiration to be over 50 per cent.…”

Photosynthesis in the Potato Under Field Conditions

“…DECKER (8) found that temperature had no effect on photosynthesis in some conifers. VERDUIN and LooMIs (24), working with maize leaves in the field, observed no correlation between moderately high temperatures and photosynthesis.…”

“…In the field, however, Q,o values near 1.0 have been demonstrated for photosynthesis within the range of 20 to 400 C (1, 6,8,23,24). Reduction in leaf hydration is assumed to check photosynth1esis.…”

Time Course of Photosynthesis in Apple Leaves Exposed to Continuous Illumination

“…KRAMER and DECKER (12) state that "in preliminary experiments at 30°C the rate of photosynthesis in oaks began to decrease rapidly after five or six hours at a high light intensity." DECKER (5) found that in preliminary measurements of the rate of photosynthesis in red alnd loblolly pines at temperatures of 20°, 300, and 400 C the rate remained unchanged for at least six hours at a light intensity of 4500 foot candles.…”