Response of Dry Matter Accumulation in Maize to Temperature: II. Leaf Photosynthesis
The response of single-leaf photosynthetic rate to temperature may be different from the response of canopy photosynthetic rate to temperature. This study was undertaken to assess the influence of the temperature response of single-leaf photosynthesis on dry matter accumulation of maize (Zea mays L.) canopies. Maize was grown in controlled-environment growth cabinets at a photosynthetic photon flux density (PPFD) of 650 μmol m−2 s−1 under five constant day/night temperature regimes (15, 19, 23, 27, 31 °C) and five differential day/night temperature regimes (15/3,19/7,23/11,27/15, 31/19 °C). Leaf photosynthetic rates were measured at the 12-leaf stage at PPFDs ranging from 0 to 2500 μmol m−2 s−1 and growth analysis was performed from planting to the 12-leaf stage. Leaf photosynthetic rate increased linearly from 15 to 27 °C and the magnitude of the response was larger at high than at low PPFD. The Q10 for specific growth rate (SGR) in the range 11 to 31 °C was 1.93 from the 4- to the 12-leaf stage (r2 = 0.89, n = 36). Leaf photosynthetic rate at 650 μmol m−2 s−1 (P650) was highly correlated with SGR across temperature regimes (r2 = 0.72, n = 60). The association between P650 and SGR could be attributed, in part, to the high correlation (r2 = 0.80, n = 60) between P650 and net assimilation rate (NAR). Leaf area ratio (LAR) contributed to the variation in SGR due to temperature and LAR was positively correlated with P650, particularly in the range 19 to 27 °C. The rate of increase of SGR from 19 to 27 °C was 32% higher than the increase of P650 over the same temperature range. Results of this study show that the temperature response of NAR of young maize canopies is similar to the temperature response of leaf photosynthetic rate, but the closeness of the relationship between NAR and P650 varied with phase of development and temperature range employed in the comparison.
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