AUTHOR=Ji Yongran , Ouzounis Theoharis , Schouten Henk J. , Visser Richard G. F. , Marcelis Leo F. M. , Heuvelink Ep 

TITLE=Dissecting the Genotypic Variation of Growth Responses to Far-Red Radiation in Tomato

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 11 - 2020

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.614714

DOI=10.3389/fpls.2020.614714

ISSN=1664-462X

ABSTRACT=Recent development of light-emitting-diodes (LEDs) and their application in modern horticulture stimulated studies demonstrating that additional far-red radiation (FR, 700-800 nm) increases plant dry mass. This effect of FR has been explained by-improved photosynthesis and/or plant architecture. However, the genotypic variation in this response is largely unknown. Here, we aim to explore and explain the genotypic variation in growth responses to additional FR. We expected genotypic variation in responses of plant dry mass to additional FR. Further, we hypothesized that a significant improvement of both net assimilation rate (NAR) and leaf area ratio (LAR) are responsible for a strong dry mass increase under additional FR, while some genotypes respond only marginally or even negatively in NAR or LAR under FR, thus resulting in a weak FR effect on plant dry mass. To test these hypotheses, we grew 33 different tomato genotypes for 21 days with 0, 25 or 100 μmol m−2 s−1 of FR added to a common white + red LED background lighting of 150 μmol m−2 s−1. Genotypes responded similarly with respect to plant height, stem dry mass and shoot: root ratio, i.e. they all increased with increasing FR. However, the response of total plant dry mass varied among genotypes. We categorized the genotypes into three groups (a strong, moderate, and weak responding group) based on their relative response in total plant dry mass to FR. Growth component analysis revealed that, the strong responding genotypes increased strongly in net assimilation rate (NAR) rather than leaf area ratio (LAR). The weak responding genotypes, however, showed a substantial increase in LAR but not NAR. The increase in LAR was due to the increase in specific leaf area. Leaf mass fraction, which is the other component of LAR, decreased with FR and did not differ between groups. In conclusion, tomato genotypes that increased strongly in NAR in response to FR were able to achieve a more substantial increase in dry mass compared to other genotypes. This is the first study to explain the differences in growth responses of a large number of tomato genotypes towards FR in their light environment.