Photosynthetica 2003, 41(4):489-495 | DOI: 10.1023/B:PHOT.0000027512.82632.7c

Different Relationship Between Electron Transport and CO2 Assimilation in two Zea mays Cultivars as Influenced by Increasing Irradiance

N. D'Ambrosio^1,*, C. Arena¹, A. Virzo de Santo¹

¹ Dipartimento di Biologia Vegetale, Università di Napoli Federico II, Napoli, Italy

Gas exchange and fluorescence parameters were measured simultaneously in two Zea mays L. cultivars (Liri and 121C D8) to assess the relationship between the quantum yield of electron transport (Φ_PS2) and the quantum yield of CO₂ assimilation (Φ_CO2) in response to photosynthetic photon flux density (PPFD). The cv. Liri was grown under controlled environmental conditions in a climate chamber (CC) while cv. 121C D8 was grown in CC as well as outdoors (OT). By exposing the two maize cultivars grown in CC to an increasing PPFD, higher photosynthetic and photochemical rates were evidenced in cv. Liri than in cv. 121C D8. In Liri plants the Φ_PS2/Φ_CO2 ratio increased progressively up to 27 with increasing PPFD. This suggests that the reductive power was more utilised in non-assimilatory processes than in CO₂ assimilation at high PPFD. On the contrary, by exposing 121C D8 plants to increasing PPFD, Φ_PS2/Φ_CO2 was fairly constant (around 11-13), indicating that the electron transport rate was tightly down regulated by CO₂ assimilation. Although no significant differences were found between Φ_PS2/Φ_CO2 of the 121C D8 maize grown under CC and OT by exposing them to high PPFD, the photosynthetic rate and photochemical rates were higher in OT maize plants.

Keywords: chlorophyll fluorescence; maize; net photosynthetic rate; photochemistry; stomatal conductance

Published: December 1, 2003Show citation