An innovative light chamber for measuring photosynthesis by three-dimensional plant organs
Résumé
Abstract
Background: In plants, three-dimensional (3-D) organs such as inflorescences or fruits carry out photosynthesis and
thus play a significant role in carbon assimilation and yield. However, this contribution has been poorly characterized
because there is no reliable method for measuring photosynthesis by 3-D organs. One of the major challenges is
ensuring the uniform irradiation of samples that are placed within a sealed chamber.
Results: In this study, we developed an innovative chamber with homogeneous lighting that can be used to measure
photosynthesis by large 3-D organs. It consisted of a 15-cm-long sealed transparent cylinder that was surrounded
by a decagonal prismatic light source, made up of a mixture of red and blue LEDs. We characterized irradiance homogeneity
within the chamber at a resolution level of 1 cm and 10°. Photosynthetic photon flux density (PPFD) along
the central axis of the chamber could be set to any value between 100 and 1100 μmol m−2 s−1. The coefficient of
variation for the irradiation values found throughout the chamber was 10% and that for the ratio of red-to-blue spectra
was less than 1.5%. The temperature of the sample was regulated to stay within 1 °C of the target temperature,
regardless of PPFD. We compared the performance of our device with that of a commercially available device employing
unidirectional lighting. Specifically, we examined net photosynthesis in two sample types—wheat ears and grape
clusters—at varying PPFD levels.
Conclusions: The devices gave similar estimates of dark respiration, regardless of sample type or age. Conversely, net
photosynthesis started to become asymptotic at lower irradiance levels in our device than in the conventional device
because apparent quantum yield was three times higher. When examining the effects of irradiance heterogeneity,
it was clear that biased estimates could result from systems employing unidirectional light sources. Our results also
confirmed that our chamber could be a useful tool for obtaining more accurate estimates of photosynthesis by 3-D
organs.
Origine | Accord explicite pour ce dépôt |
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