Adjustments of net photosynthesis in Solanum tuberosum in response to reciprocal changes in ambient and elevated growth CO2 partial pressures

Single leaf photosynthetic rates and various leaf components of potato (Sol anum tuberosum L,) were studied 1-3 days after reciprocally transferring pl ants between the ambient and elevated growth CO2 treatments. Plants were ra ised from individual tuber sections in controlled environment chambers at e ither ambient (36 Pa) or elevated (72 Pa) CO,. One half of the plants in ea ch growth CO2 treatment were transferred to the opposite CO2 treatment 34 d ays after sowing (DAS), Net photosynthesis (P-n) rates and various leaf com ponents were then measured 34, 35 and 37 DAS at both 36 and 72 Pa CO2. Thre e-day means of single leaf P-n rates, leaf starch, glucose, initial and tot al Rubisco activity, Rubisco protein, chlorophyll (a + b), chlorophyll (a/b ), alpha -amino N, and nitrate levels differed significantly in the continu ous ambient and elevated CO2 treatments. Acclimation of single leaf P-n rat es was partially to completely reversed 3 days after elevated CO2-grown pla nts were shifted to ambient CO2, whereas there was little evidence of photo synthetic acclimation 3 days after ambient CO2-grown plants were shifted to elevated CO2. In a four-way comparison of the 36, 72, 36 to 72 (shifted up ) and 72 to 36 (shifted down) Pa CO2 treatments 37 DAS, leaf starch, solubl e carbohydrates, Rubisco protein and nitrate were the only photosynthetic f actors that differed significantly. Simple and multiple regression analyses suggested that negative changes of P-n in response to growth CO2 treatment were most closely correlated with increased leaf starch levels.