Relation of CO₂ Compensation Concentration to Apparent Photosynthesis in Maize

Abstract

,1u CO2/l air) for species with inefficient photosynthesis and high photorespiration, and low (<10 pI CO2/l air) for species with efficient photosynthesis and negligi-ble photorespiration (4,16,25,26).Maize belongs to this latter group (14, 16), and has a rCO2L, independent of°2 concentration (15,20).Recent models demonstrate that the magnitude of the [CO2], depends upon the diffusive resistance of the leaf to CO2, the efficiency of CO2 fixation in the chloroplasts, and the respiration rate of the leaf (1,21,24).A second, lesser used, method exists for predicting the photosynthetic efficiency of leaves. The Michaelis constant (Km) of a leaf has been postulated (7) as "the external CO2 concentration which enables the leaf, at saturating light intensity, to fix CO2 at half the maximal velocity". The Km depends upon the affinity of the carboxylating enzymes for CO2, the diffusive resistance of the leaf, and the rate of respiration. Thus Zelitch (27), whose convention we adopt, designates the Km for a leaf as an "overall Michaelis constant". Goldsworthy (7) and Zelitch (27) found that the Km for photosynthesis of maize was only 10 to 15 % lower than tobacco

Photosynthetic Properties and Root Chilling Responses of Altitudinal Ecotypes of Typha Latifolia L.

“…It has been suggested that compensation point is the level of C0 2 at which gross photosynthesis and photorespiration just balance one another (Heichel and Musgrave 1969). It has been suggested that compensation point is the level of C0 2 at which gross photosynthesis and photorespiration just balance one another (Heichel and Musgrave 1969).…”

Studies on the Mechanism of Glycerate 3-Phosphate Synthesis in Tomato and Maize Leaves

“…The high affinity for CO2 in maize leaves could be caused by the nature of the irreversible reaction which is involved in feeding the CO2 reserve (24,27). Thus a possible explanation of the low compensation point found in maize (10,23,30) …”

Designing a Peanut Ideotype for a Target Environment Using the CSM‐CROPGRO‐Peanut Model

“…The SLAVR is a measure of leaf area per unit of leaf dry weight and is negatively associated with the rate of photosynthesis. This has been shown for several crops, including alfalfa (Medicago sativa L.) (Pearce et al, 1969), maize (Heichel and Musgrave, 1969), soybean (Dornhoff and Shibles, 1976), oat (Avena sativa L.) (Criswell and Shibles, 1971) Figure 2. Effects of changing the number of photothermal days from emergence to fl owering (EMFL) and the number of photothermal days from fi rst seed to physiological maturity (SDPM) simultaneously in opposite direction (a and b) in Step 1 and changing the number of photothermal days from fi rst fl owering to end of leaf expansion (FLLF) (c and d) in Step 2 on fi nal biomass and seed yield averaged over 10 locations, three growing seasons, and 30 yr .…”

“…Second, the realizable gain from higher LFMAX could be less than Fig. 3 indicates because increased LFMAX has been reported to be positively associated with decreased SLAVR (Irvine, 1967;Heichel and Musgrave, 1969;Pearce et al, 1969;Criswell and Shibles, 1971;Dornhoff and Shibles, 1976;Wright et al, 1988), so there is a partial confl ict of simultaneous increases in both SLWVR and LFMAX. Analyses by Boote et al (2003) illustrate the importance of considering photosynthesis increases, with coupling or uncoupling of LFMAX to SLAVR.…”

“…This selected value was only 2.3 μmol CO 2 m -2 s -1 more than both the original L-and S-lines (Table 3) and only 2.3 μmol CO 2 m -2 s -1 higher than used for the standard Florunner cultivar for which the peanut model was predominantly calibrated and tested with both leaf-level and canopylevel photosynthesis . 3 indicates because increased LFMAX has been reported to be positively associated with decreased SLAVR (Irvine, 1967;Heichel and Musgrave, 1969;Pearce et al, 1969;Criswell and Shibles, 1971;Dornhoff and Shibles, 1976;Wright et al, 1988), so there is a partial confl ict of simultaneous increases in both SLWVR and LFMAX. For these reasons, we believe the search range for LFMAX is sufficiently conservative.…”