Anthracnose in açaí palm leaves reduces leaf gas exchange and chlorophyll a fluorescence

Abstract

Leaf spots caused by Colletotrichum sp. decrease photosynthesis rate and hamper the growth of açaí seedlings in nurseries. The objective of the study was to quantify the changes in the photosynthetic performance of açaí leaves inoculated with Colletotrichum sp. through measurements of gas exchange, chlorophyll a fluorescence, and photosynthetic pigments. The rate of net CO2 assimilation, stomatal conductance, transpiration rate, chlorophyll a and b, ratio of chlorophyll a/b and total chlorophyll decreased, but the intercellular CO2 concentration increased in inoculated plants compared with non-inoculated plants. Changes in chlorophyll a fluorescence began at 3 days after inoculation (dai) and increased with the number of injuries. The maximum photochemical efficiency ratio (Fv/Fm) declined sharply as well as other characteristics of chlorophyll a fluorescence, such as the photochemical quenching coefficient, effective quantum yield of PSII, quantum yield of non-regulated energy dissipation, and electron transfer rate. Infection by Colletotrichum sp. reduces the photosynthetic performance due to reduced light capture and assimilation of CO2 in the mesophyll. Gas exchange and chlorophyll a fluorescence can describe reductions in photosynthetic capacity caused by anthracnose in leaves.