Changes in the photosynthetic light response curve during leaf development of field grown maize with implications for modelling canopy photosynthesis

Abstract

Changes in the photosynthetic light-response curve during leaf development were determined for the fourth leaf of maize crops sown on 23 April and 10 June. Temperatures were unusually mild during late spring/early summer and neither crop experienced chilling damage. The concept of thermal time was used to take into account the effects of different temperature regimes on developmental stage, thereby enabling photosynthetic light-response data to be combined for both crops to describe the general response. Large variations in the upper asymptote (Asat) and convexity (Θ) of the light-response curve occurred during leaf development, but the maximum quantum yield of CO2 assimilation remained relatively constant throughout. Dark respiration rates showed a small but significant decrease with leaf age and generally ranged between 5 and 10% of Asat. A simple mathematical model was developed to assess the sensitivity of daily leaf photosynthesis (AL) to reductions in the Asat, Θ and the initial slope (Φ) of the light-response curve at different stages of leaf development. On bright sunny days, and at all developmental stages, AL was ca. twice as sensitive to reductions in Asat than to reductions in Φ and Θ. In overcast conditions, however, all three parameters contributed significantly to reductions in leaf photosynthesis, although the contribution of Φ was greatest during early leaf growth, while older leaves were most sensitive to depressions in Asat. The implications of these results for modelling the sensitivity of canopy photosynthesis to chill-induced photoinhibition of the light-response curve are discussed.

Evaluation of JULES-crop performance against site observations of irrigated maize from Mead, Nebraska

“…In the literature, the photosynthetic capacity of maize leaves (per leaf area) declines with age and the older leaves are lower in the canopy Dwyer and Stewart (1986);Stirling et al (1994). As discussed in Sect.…”

“…In addition, Stirling et al (1994) shows a strong dependence in dark respiration in maize over time (using fits to light response curves), which can not be captured in JULES: at degree day 220 (roughly where the leaf area reaches a maximum), it is approximately twice as high at degree day 50. As we have discussed, maintenance respiration and V cmax covary in JULES, but the growth respiration is linked to net primary productivity, which increases in the crop up until approximately anthesis.…”

Photosynthetic light response curves determined with the leaf oxygen electrode: minimisation of errors and significance of the convexity term

“…Some workers prefer to go even further and ensure that the magnitude of h exerts no in¯uence on that of a¢; in such cases, a¢ is usually estimated separately using linear regression, whilst P max is derived from the non-linear model (e.g. Leith and Reynolds 1987;Stirling et al 1994;Cannell and Thornley 1998). It should be noted that from a purely theoretical viewpoint, h exerts no in¯uence on the magnitude of either a (at I=0) or P max (at I=¥), but in practice regression through a ®nite number of data points will generate some dependence.…”

Internal and external photoprotection in developing leaves of the CAM plant Cotyledon orbiculata

“…In addition to lower light reflectivity, young emerging leaves typically have lower photosynthetic capacities (^max) than mature leaves (Constable & Rawson 1980;Leech & Baker 1983;Ticha et al 1985;Wullschleger & Oosterhuis 1990;Stirling et al 1994). Eor young leaves, light levels may be saturating and in excess of the capacity for photosynthetic utilization at much lower light intensities than in older leaves leaving the former more susceptible to photoinhibition.…”