Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System
Tryptophan is a precursor of indole-3-acetic acid (IAA), which is the major auxin involved in the regulation of lateral root formation. In this study, we used a scanner-based rhizotron system to examine root growth and morphological responses of soybean (<i>Glycine max</i>, ‘Golden Harve...
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MDPI AG
2023-01-01
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| Online Access: | https://www.mdpi.com/2223-7747/12/1/186 |
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| author | Atsushi Sanada Shinsuke Agehara |
| author_facet | Atsushi Sanada Shinsuke Agehara |
| author_sort | Atsushi Sanada |
| collection | DOAJ |
| description | Tryptophan is a precursor of indole-3-acetic acid (IAA), which is the major auxin involved in the regulation of lateral root formation. In this study, we used a scanner-based rhizotron system to examine root growth and morphological responses of soybean (<i>Glycine max</i>, ‘Golden Harvest’) seedlings to exogenous tryptophan. Seeds were sown directly in the rhizotron filled with field soil. Tryptophan was applied at 1.9 and 3.8 mg plant<sup>−1</sup> by soil drenching or foliar spray. Canopy and root projected area were monitored by analyzing canopy and rhizotron images using ImageJ software. Seedlings were sampled at the first trifoliate stage, 18 days after sowing (DAS), and root morphology was determined by analyzing washed root images using WinRHIZO software. According to contrast analysis, when all tryptophan treatments were pooled, tryptophan application increased canopy and root projected area by 13% to 14% compared with the control at 18 DAS. Tryptophan application also increased root dry matter accumulation by 26%, root:shoot ratio by 24%, and secondary root number by 13%. Tryptophan applied by soil drenching also increased root length and surface area of fine roots (<0.2 mm diameter) by 25% and 21%, respectively, whereas it slightly inhibited primary root elongation. The efficacy of tryptophan soil drenching in stimulating root formation became greater with increasing the application rate. These results suggest that exogenous tryptophan induces auxin-like activities in root development. Soil drenching of tryptophan appears to be an effective strategy in improving the establishment of soybean. Importantly, this strategy is easily implementable by commercial growers with no negative side effect. |
| first_indexed | 2024-03-09T03:27:34Z |
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| id | doaj.art-9e4059749d3d49b5a5b1daa65820453d |
| institution | Directory Open Access Journal |
| issn | 2223-7747 |
| language | English |
| last_indexed | 2024-03-09T03:27:34Z |
| publishDate | 2023-01-01 |
| publisher | MDPI AG |
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| series | Plants |
| spelling | doaj.art-9e4059749d3d49b5a5b1daa65820453d2023-12-03T15:00:45ZengMDPI AGPlants2223-77472023-01-0112118610.3390/plants12010186Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron SystemAtsushi Sanada0Shinsuke Agehara1Department of International Agricultural Development, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, JapanGulf Coast Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 14625 CR 672, Wimauma, FL 33598, USATryptophan is a precursor of indole-3-acetic acid (IAA), which is the major auxin involved in the regulation of lateral root formation. In this study, we used a scanner-based rhizotron system to examine root growth and morphological responses of soybean (<i>Glycine max</i>, ‘Golden Harvest’) seedlings to exogenous tryptophan. Seeds were sown directly in the rhizotron filled with field soil. Tryptophan was applied at 1.9 and 3.8 mg plant<sup>−1</sup> by soil drenching or foliar spray. Canopy and root projected area were monitored by analyzing canopy and rhizotron images using ImageJ software. Seedlings were sampled at the first trifoliate stage, 18 days after sowing (DAS), and root morphology was determined by analyzing washed root images using WinRHIZO software. According to contrast analysis, when all tryptophan treatments were pooled, tryptophan application increased canopy and root projected area by 13% to 14% compared with the control at 18 DAS. Tryptophan application also increased root dry matter accumulation by 26%, root:shoot ratio by 24%, and secondary root number by 13%. Tryptophan applied by soil drenching also increased root length and surface area of fine roots (<0.2 mm diameter) by 25% and 21%, respectively, whereas it slightly inhibited primary root elongation. The efficacy of tryptophan soil drenching in stimulating root formation became greater with increasing the application rate. These results suggest that exogenous tryptophan induces auxin-like activities in root development. Soil drenching of tryptophan appears to be an effective strategy in improving the establishment of soybean. Importantly, this strategy is easily implementable by commercial growers with no negative side effect.https://www.mdpi.com/2223-7747/12/1/186auxin precursorbiostimulantimage analysisrhizosphereroot morphology |
| spellingShingle | Atsushi Sanada Shinsuke Agehara Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System Plants auxin precursor biostimulant image analysis rhizosphere root morphology |
| title | Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System |
| title_full | Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System |
| title_fullStr | Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System |
| title_full_unstemmed | Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System |
| title_short | Characterizing Root Morphological Responses to Exogenous Tryptophan in Soybean (<i>Glycine max</i>) Seedlings Using a Scanner-Based Rhizotron System |
| title_sort | characterizing root morphological responses to exogenous tryptophan in soybean i glycine max i seedlings using a scanner based rhizotron system |
| topic | auxin precursor biostimulant image analysis rhizosphere root morphology |
| url | https://www.mdpi.com/2223-7747/12/1/186 |
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