Cross-sections of legume leaves

Sink-source imbalance and down-regulation of photosynthesis

Sink-source imbalance could cause accumulation of total non-structural carbohydrates (TNC) and down-regulation of photosynthesis. Sugiura et al. investigate how sink-source imbalance causes photosynthetic down-regulation in soybean (Glycine max), French bean (Phaseolus vulgaris), and azuki bean (Vigna angularis).

Cross-sections of legume leaves

Among the three legume plants, maximum photosynthesis was down-regulated with increase in TNC only in French bean, whereas decrease in sink-source ratio caused anatomical changes and increase in cell wall content in source leaves, especially in soybean. The results suggest that down-regulation of photosynthesis is caused not only physiologically such as through a decrease in Rubisco, but also morphologically, such as through an increase in cell wall thickness that could reduce chloroplast CO2 concentration.

Alex Assiry

Alex Assiry is an editorial assistant in the Annals of Botany Office. When not working, Alex listens for the opportunity to help.

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