New research reveals that a majority of crops plan ahead for a lack of light and modify their growth to acclimatise and prosper. After detecting the proximity of vegetation, some plants, including most of the crops we eat, can plan for conditions of shade in their surroundings and modify their structure and growth to prosper with less light. This has been verified by a research group of the Plant Molecular and Cellular Biology Institute (IBMCP), mixed centre of the Polytechnic University of Valencia (UPV) and the Spanish National Research Council (CSIC), in collaboration with the Centre for Research on Agricultural Genomics (CRAG) of Barcelona. The researchers observed that the fall in the levels of photosynthetic pigments of the plants is a mechanism that allows them to adapt to living with less light, thus planning ahead for a possible future in the shade.
In order to perform photosynthesis, plants absorb specific regions of the electromagnetic spectrum, blue and red, and let the far-red pass through or reflect it. Thus, when the sunlight filters through the leaves, it loses blue and red (which is absorbed and used for photosynthesis) and has is strong in far-red. These changes in the quality of the light are a sign that other plants recognise as generated by the proximity of neighbouring plants (and thus of competitors for resources), and use it to trigger a series of responses known as the shade avoidance syndrome (SAS).
The teams led by researchers from the CSIC at the IBMCP, Jaume Martínez García and Manuel Rodríguez Concepción, studied the response to changes in the quality and amount of light from different species of Brassicaceae, a family which includes important crops such as cabbage, cauliflower, broccoli, rapeseed, radish or mustard. Thus, they classified the species into two groups: those that avoid the shade and those that tolerate it. The former grew better at high-intensity levels of light and elongated significantly upon sensing the signal of vegetable proximity. Those that tolerate the shade, however, barely elongated with this signal and adapted better to live with little light.
Furthermore, they observed that, when the species that avoid the shade were exposed to the signal that notified the proximity of vegetation and grew with less light, their photosynthetic efficiency was better than that of the plants that had not been previously exposed to this signal. “We observed that this was due not only to a decrease in the levels of photosynthetic pigments but also to changes in the expression of genes and chloroplast structures linked to photosynthesis,” explains Manuel Rodríguez. Furthermore, the researchers verified that the mutant plants, unable to translate the signal of the proximity of other plants, and the species that tolerate the shade did not show this adaptive response.
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Morelli, L., Paulisic, S., Qin, W., Iglesias-Sanchez, A., Roig-Villanova, I., Florez-Sarasa, I., Rodriguez-Concepción, M., Martínez-García, J.F. Light signals generated by vegetation shade facilitate acclimation to low light in shade-avoider plants. Plant Physiology 2021. DOI: https://doi.org/10.1093/plphys/kiab206