Better with far red light
Plants use light for their growth. To be more specific, they use the photons from blue and red light. Now Now Dutch researchers show that in addition, photons from far-red light can contribute to the conversion of CO2 to sugars.
Plants use far red light it to figure out if they are getting shaded over. Leaves mostly absorb red light, and allow far red light to pass through. This is why the ratio red to far red light decreases with the amount of overhanging leaves. But far red light can also make photosynthesis more efficient. Although, there is no photosynthesis when plants are only receiving far-red light. This effect the researchers decided to investigate using rice plants.
Rice plants were growing better when they get during the day an extra dose of far red light in addition to their normal amount of white light. But far red light appeared not to have any effect on gene expression. Moreover, the extra growth was only there when the extra dose of red light was received simultaneously with the white light. Giving the plants an extra dose of far red light at the end of the day did not make the plants grow better.
An extra bit of far red light rice plants make their photosynthesis more efficient
To decipher this further the researchers studied the leaves. Even though plants had increased leave size when growing in white and far red light, they did not have extra stomata. And the leaves were also paler, they had fewer chloroplasts. The opposite of what you might be expecting of plants that grew better. Lastly the researchers studied the photosynthetic activity. This appeared to be increased in plants that grew in white light supplemented with far red light.
Growing in the shadow does not have to be the end of photosynthesis. As long as there is enough red and blue light, and extra bit of far red light might make photosynthesis even more efficient. Although the study also showed that the amount of increased efficiency depended of the variety of the rice plants. Some variety get more out the extra far red light photons that another variety.
Literature
Huber, M., de Boer, H.J., Romanowski, A., van Veen, H., Buti, S., Kahlon, P.S. et al. (2024) Far-red light enrichment affects gene expression and architecture as well as growth and photosynthesis in rice. Plant, Cell & Environment, 1–18. https://doi.org/10.1111/pce.14909
Plant en Zo 