Abstract
In soybean production, the shade avoidance response can affect yield negatively in both mono- and inter-cropping systems due to increased heterogeneity of the crop and lodging. This is mainly regulated by photoreceptors responding to the ratio between red and far-red light (R:FR) and photosynthetic photon flux density (PPFD). In this study, three soybean cultivars were grown under different R:FR and PPFD in a light emitting diode (LED) climate chamber to disentangle the effect of each on morphology and dry matter. Results showed that plant organs were influenced differently and indicated an interaction with the increase in assimilates at high PPFD. Internode elongation was mainly influenced by low PPFD with an additive effect from low R:FR, whereas petiole elongation responded strongly under low R:FR. Hence, petiole elongation can be seen as the main response to the threat of shade (high PPFD and low R:FR) and both petiole and internode elongation as a response to true shade (low PPFD and low R:FR). Interactions between cultivar and light treatment were found for internode length and diameter and leaf mass ratio, which may be unique properties for specific cropping systems.
Highlights
Plants competing for light recognize neighboring vegetation through changes in the light quality, which leads to shade avoidance responses (SARs), with the aim to increase light interception and competitiveness
Plant weight decreased under low photosynthetic photon flux density (PPFD) and increased under low R:far-red light (FR) (Table 3)
The results showed that the response of soybean to low PPFD and low R:FR can be characterized as an interactive response with differences between organs
Summary
Plants competing for light recognize neighboring vegetation through changes in the light quality, which leads to shade avoidance responses (SARs), with the aim to increase light interception and competitiveness. A reduction in red to far-red ratio (R:FR) while photosynthetic photon flux density (PPFD) is still high, appears by the threat of future shade from surrounding short vegetation [3,4]. In this situation, FR is reflected from the surrounding vegetation, whereas red light (R) is absorbed and decreases the R:FR perceived by the taller crop. FR is reflected from the surrounding vegetation, whereas red light (R) is absorbed and decreases the R:FR perceived by the taller crop Under shading, both perceived PPFD and R:FR are reduced, due to the high absorption of other wavelengths when compared to FR by the tall vegetation
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