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Leaf Gas Exchange and Chlorophyll a Fluorescence Imaging of Rice Leaves Infected with Monographella albescens

February 2015 , Volume 105 , Number  2
Pages  180 - 188

Sandro Dan Tatagiba, Fábio Murilo DaMatta, and Fabrício Ávila Rodrigues

First and second authors: Universidade Federal de Viçosa (UFV), Departamento de Biologia Vegetal, 36570-900, Viçosa, Minas Gerais State, Brazil; and third author: UFV, Departamento de Fitopatologia, Laboratório da Interação Planta-Patógeno, 36570-900, Viçosa, MG, Brazil.

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Accepted for publication 6 August 2014.

This study was intended to analyze the photosynthetic performance of rice leaf blades infected with Monographella albescens by combining chlorophyll (Chl) a fluorescence images with gas exchange and photosynthetic pigment pools. The net CO2 assimilation rate, stomatal conductance, transpiration rate, total Chl and carotenoid pools, and Chl a/b ratio all decreased but the internal CO2 concentration increased in the inoculated plants compared with their noninoculated counterparts. The first detectable changes in the images of Chl a fluorescence from the leaves of inoculated plants were already evident at 24 h after inoculation (hai) and increased dramatically as the leaf scald lesions expanded. However, these changes were negligible for the photosystem II photochemical efficiency (Fv/Fm) at 24 hai, in contrast to other Chl fluorescence traits such as the photochemical quenching coefficient, yield of photochemistry, and yield for dissipation by downregulation; which, therefore, were much more sensitive than the Fv/Fm ratio in assessing the early stages of fungal infection. It was also demonstrated that M. albescens was able to impair the photosynthetic process in both symptomatic and asymptomatic leaf areas. Overall, it was proven that Chl a fluorescence imaging is an excellent tool to describe the loss of functionality of the photosynthetic apparatus occurring in rice leaves upon infection by M. albescens.

Additional keywords: photosynthesis.

© 2015 The American Phytopathological Society