Quantitative effects of temperature and light intensity on PSII efficiency of mango leaves under artificial and natural conditions

Abstract

Mango is a chilling-sensitive evergreen fruit tree of tropical origin. In different seasons, mango leaves with different predawn Fv/Fm, due to the variation of minimum air temperature before sunrise (Tmin), were selected to measure actual quantum efficiency of PSII at various temperatures and light intensities under natural and artificial conditions. Relationships of PSII efficiency (ΦPSII, Fv/Fm at predawn or during illumination) and photosynthetic photon flux density (PPFD or E) measured under a given temperature of artificial condition, could be fitted well by equations: ΦPSII = a1 + b1 × c1E and ΦPSII = a2 + b2 × E/(c2 + E). Both a1 + b1 and a2 were close to the measured predawn Fv/Fm, and b1 and b2 showed positive and negative linear correlation, respectively, with predawn Fv/Fm. Both c1 and c2 showed a significant curvilinear correlation with temperature during illumination (T), and predawn Fv/Fm showed a significant curvilinear correlation with Tmin. By combining the above relationships, we obtained 2 empirical regression models: ΦPSII = −0.016 + 0.129 × (1.036 − 6.359/Tmin) + [0.019 + 0.866 × (1.036 − 6.359/Tmin)] × (1.004 − 0.153/T)E and ΦPSII = −0.003 + 1.013 × (1.036 − 6.359/Tmin) + [0.093 − 1.194 × (1.036 − 6.359/Tmin)] × E/[(24.690 × exp0.095T) + E]. ΦPSII estimated from these 2 equations was highly correlated with measured ΦPSII (r2 = 0.920 and 0.930, respectively, P < 0.001), and a nearly 1:1 correlation line could be plotted, even when merging data from both natural and artificial conditions. With just 3 easily obtainable meteorological variables, these 2 empirical regression models could be used to simulate seasonal and diurnal dynamic variations in PSII efficiency in mango leaves.