How Plants Use Light and Heat Affects Crop Growth Efficiency

Jenn Hoskins
15th January, 2024

How Plants Use Light and Heat Affects Crop Growth Efficiency
Improving crop yields is a central challenge in agriculture, and a key factor determining how efficiently a crop grows is its ability to convert sunlight into biomass – a measure known as radiation use efficiency (RUE). While it’s known that different varieties of crops like maize and sorghum have varying RUE levels, the underlying reasons for these differences haven’t been fully understood. Researchers at the University of Queensland (UQ)[1] have recently investigated this, aiming to pinpoint the specific leaf-level processes that contribute to variations in RUE at the whole-crop level. The study focused on elite varieties of maize and grain sorghum, employing a novel approach that combined detailed measurements of leaf photosynthesis with sophisticated computer modelling. Traditionally, understanding photosynthesis has involved studying individual leaves in controlled environments. However, this doesn’t always translate well to the complex reality of a crop canopy where light, temperature, and carbon dioxide levels vary significantly. This research took a “top-down” approach, meaning it started with observations of the entire canopy and worked backwards to identify the crucial leaf-level traits. A key innovation was the development of a new method for measuring how leaves respond to different levels of carbon dioxide, light, and temperature simultaneously. This data was then fed into a Bayesian model – a statistical technique that allows researchers to estimate the values of multiple parameters at once, even when the data is incomplete or noisy. The model used was specifically designed for C4 plants, a group that includes maize and sorghum, and incorporates established understanding of their photosynthetic processes. This builds on previous work that highlighted the importance of modelling photosynthesis to understand gas exchange and potential improvements to C4 pathways[2]. The analysis revealed statistically significant differences in several leaf-level photosynthetic parameters between the maize and sorghum varieties. Notably, differences were found in the quantum yield of photosynthesis – a measure of how efficiently leaves convert light energy into chemical energy – and in the maximum activity of key enzymes involved in carbon fixation, specifically Rubisco and PEPc. These enzymes are critical for the initial steps of converting carbon dioxide into sugars. The study showed these differences weren’t constant, but varied depending on leaf temperature. To understand how these leaf-level differences impacted overall crop performance, the researchers used the inferred photosynthetic parameters to simulate diurnal (daily) canopy photosynthesis. These simulations demonstrated that the photosynthetic response to low light, and how that response changes with temperature, were major drivers of differences in crop-level RUE. This aligns with earlier research demonstrating that canopy architecture significantly influences light distribution and, consequently, photosynthetic productivity[3]. The UQ team’s work expands on this by identifying which photosynthetic traits are most sensitive to these architectural effects. The findings suggest that improving the low-light photosynthetic response, and ensuring it’s appropriately tuned to temperature variations, could be a key strategy for increasing RUE in both maize and sorghum. The study generates specific, testable hypotheses for future research, potentially guiding efforts in plant breeding and genetic engineering to develop more efficient crops. The ability to accurately model canopy photosynthesis, as demonstrated in this study, also provides a valuable tool for predicting the performance of different crop varieties under various environmental conditions, and for optimizing crop management practices.

AgricultureEnvironmentBiochem

References

Main Study

1) Contrasting leaf-scale photosynthetic low-light response and its temperature dependency are key to differences in crop-scale radiation use efficiency.

Published 12th January, 2024

https://doi.org/10.1111/nph.19537

Related Studies

2) Updating the steady-state model of C4 photosynthesis.

https://doi.org/10.1093/jxb/erab266

3) High-Resolution Three-Dimensional Structural Data Quantify the Impact of Photoinhibition on Long-Term Carbon Gain in Wheat Canopies in the Field.

https://doi.org/10.1104/pp.15.00722


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