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Chamber‐based system for measuring whole‐plant transpiration dynamics

ABSTRACT: Abstract Most of our insights on whole‐plant transpiration (E) are based on leaf‐chamber measurements using water vapor porometers, IRGAs, or flux measurements. Gravimetric methods are integrative, accurate, and a clear differentiation between evaporation and E can be made. Water vapor pressure deficit (VPD) is the driving force for E but assessing its impact has been evasive, due to confounding effects of other climate drivers. We developed a chamber‐based gravimetric method, in which whole plant response of E to VPD could be assessed, while keeping other environmental parameters at predetermined values. Stable VPD values (0.5–3.7 kPa) were attained within 5 min after changing flow settings and maintained for at least 45 min. Species differing in life form and photosynthetic metabolism were used. Typical runs covering the range of VPDs lasted up to 4 h, preventing acclimation responses or soilborne water deficit. Species‐specific responses of E to VPD could be identified, as well as differences in leaf conductance. The combined gravimetric‐chamber‐based system presented overcomes several limitations of previous gravimetric set ups in terms of replicability, time, and elucidation of the impact of specific environmental drivers on E, filling a methodological gap and widening our phenotyping capabilities. Most insights on transpiration (E) are based on leaf‐chamber measurements using water vapor porometers, IRGAs, or flux measurements. We developed a chamber‐based gravimetric method, to unequivocally assess plant response of E to VPD. The result is an affordable and reliable system that can be used to study the interaction between atmosphere and E at the whole‐plant level.

SUBMITTER: Pieters A

PROVIDER: S-EPMC10168032 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Project description:BackgroundIn 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.ResultsIn 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.ConclusionsThe 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.

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Chamber‐based system for measuring whole‐plant transpiration dynamics

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