Abstract
The influence of temperature on the CO2 exchange rates was investigated in winter rape plants (Brassica napus L. var. oleifera cv. Górczański) subjected to cold (2°C) pretreatment. After one or two days of cold pretreatment both photosynthesis and dark respiration still readily responded to changes in the temperature of measurement. Prolongation of plant exposure to cold caused not only a marked depression of photosynthesis but also photosynthesis became less temperature and light dependent. In contrast, prolonged cold pretreatment only slightly affected the sensitivity of dark respiration to temperature. In the cold‐pretreated plants the rate of dark respiration was higher that that in the untreated ones at comparable temperatures of measurement. To obtain a full reversion of the cold‐induced changes in photosynthesis and dark respiration rates the plants had to be exposed to higher (25°C) temperature for 3–7 days.It seems that low temperature brings about two types of effects in plants with regard to photosynthesis and respiration: a direct response consisting in the rapid and readily reversible reduction of both photosynthesis and respiration; and an indirect one which consists in long lasting modifications of photosynthesis and dark respiration rates and may be related to the cold‐induced changes in biochemical properties in photosynthetic and respiratory systems.
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