Changes in the rates of apparent photosynthesis in 21% and 1% oxygen and of dark respiration following a single exposure of three-year-old Pinus strobus L. Plants to gamma radiation

Abstract

Rates of apparent photosynthesis (in 21 per cent and 1 per cent oxygen) and dark respiration were measured 1–21 days following a single exposure of young white pines to doses of gamma radiation ranging from approximately 230–7500 rad. At all dose levels, the rates of apparent photosynthesis were reduced. The per cent change in the rates at both O 2 concentrations following irradiation were similar suggesting that the initial response was at the photosystem level. In contrast to photorespiration which was probably reduced by the radiation, the rate of dark respiration, though unchanged one day after radiation, increased thereafter. The data reaffirm the sensitivity of the photosynthetic capacity of white pines to ionizing radiation and the differential response of the chloroplast and mitochondrion organelles.