Fluorescence parameters among leaf photosynthesis-related traits are the best proxies for CO2 assimilation in Central Amazon trees

Abstract

We investigated whether photosynthesis along the vertical profile of tropical forest can be represented by JIP-test parameters derived from the fluorescence induction curve instead of more commonly utilized traits. Photosynthesis-related traits were measured during four seasons in 45 trees along a vertical forest profile in the Central Amazon, and their combined (interspecific) correlations with canopy openness and PNmax (light-saturated photosynthesis) were examined. PNmax, canopy openness, the efficiency of electron transport in PSI (IP-phase and RE0/ET0), leaf mass per area and leaf phosphorus content had strong positive correlations (r > 0.6). JIP-test parameters related to the final steps of electron transport (IP-phase, RE0/ET0 and PItotal) were good predictors of PNmax during all seasons, whereas stomatal conductance had the strongest correlation with PNmax during the dry season. The JIP-test parameters related to PSII efficiency (PIABS and FV/FM) were poorly associated with PNmax. Therefore, the PNmax variation along the vertical profile of Central Amazonian forest can be represented by JIP-test parameters, especially those related to the final steps of the electron transport chain.