Čatský J., Pospíšilová J., Solárová J., Synková H., Wilhelmová N.
BIOLOGIA PLANTARUM 37: 35-48, 1995

Keywords: leaf gas exchange, chlorophyll fluorescence, thylakoid structure, Phaseolus vulgaris, plantlet ontogeny
Abstract: Abstract Limitations on photosynthesis, characterized by leaf CO2 exchange, chlorophyll fluorescence, and thylakoid structure, were studied under environmental conditions simulating culture in vitro. These were simulated by growing Phaseolus vulgaris plants in nutrient solution under high relative humidity of air (> 90 %), and CO 2 concentrations (Ca) that decreased with the development of photosynthetic activities during plant ontogeny (1200"to 300 mg m-3). The ontogeny of such model plants was more rapid, primary leaves reached photosynthetic maturity 2 to 3 d earlier and their life span was 7 to 14 d shorter than in control plants. Their photosynthetic activity in situ was limited, after reaching "photosynthetic maturity", similarly to plants grown in vitro. When measured under optimal conditions, however, 50 to 70 % higher net photosynthetic rates (PN) were found in leaves of different ages as compared with plants grown under c a of 700 mg m -3 and a lower air humidity (30 - 35 %). This increase in PN was associated with a high conductance for CO 2 transfer by adaxial and abaxial epidermes. In model plants, the dark respiration rate (RD) was almost twice that in the control, while the photorespiration rates were similar to controls; CO 2 compensation concentration was about 50 % of that in controls. The ratios PN/RD were similar in control and in model plants. Chlorophyll a+b content in leaves of the model plants was lower than that in the control plants. Grana extent increased with plant age in the model plants while it decreased in the control ones. In both the stromal and granal membranes of the chloroplasts in model plants, a marked accumulation of carotenoids occurred independent of age.
DOI: 10.1007/BF02912996 IEB authors: Jana Pospíšilová