Foliar uniconazole application increases rice lodging resistance by altering stem morphological and anatomical traits

Abstract

Lodging is a limiting factor for rice production in the Sichuan Basin, China. However, the mechanisms of stem lodging resistance, especially its regulation by plant growth regulators are still unclear. A two-year field study, by using the three foliar application rates of uniconazole with two rice varieties, Yuxiang203 (YX203) and Cliangyouhuazhan (CLYHZ), was conducted to determine stem lodging resistance and its morphological and anatomical mechanisms in rice plants. The results revealed that, compared with 2019, the grain yield in 2020 significantly decreased, while the lodging index (LI) significantly increased. Uniconazole treatment increased the rice yield by 4.6%-11.2% and 2.1%-7.0%, and decreased LI by 21.1%-33.9% and 11.4%-29.6% in YX203 and CLYHZ, respectively. Uniconazole treatment shortened the length of the basal internodes by 19.5%-33.0% (YX203) and 24.7%-40.7% (CLYHZ), resulting in a significant reduction in plant height. Uniconazole treatment increased the mechanical tissue thickness, areas of small and larger vascular bundles, and culm diameter, and further increased the breaking strength of the two varieties. Cell wall components, including cellulose and lignin, were increased by foliar application of uniconazole, thereby creating denser sclerenchyma cells and increasing the thickness of the mechanical tissue and area of the vascular bundle. These results suggest that the application of uniconazole enhances stem mechanical strength via increased mechanical tissue thickness and larger areas of small and large vascular bundles, thereby improving the lodging resistance of rice plants.

Keywords

Anatomical traits / Grain yield / Lodging resistance / Morphological traits / Rice / Uniconazole

Abbreviations

ALVB area of large vascular bundle

ASVB area of small vascular bundle

BS bending stress

CLYHZ Cliangyouhuazhan

DWIC dry weight per cm of N₅ internode culm

DWILS dry weight per cm of N₅ internode leaf sheath

FW fresh weight from the broken point to the panicle top

GCH gravity center height

LI lodging index

M breaking strength

NLVB number of large vascular bundle

NSC non-structural carbohydrate

NSVB number of small vascular bundle

SL distance from the broken point to the panicle top

SM section modulus

WP bending moment of the whole plant

YX203 Yuxiang203

Availability of data and materials

Data will be shared upon request by readers.

Authors' contributions

W.Z. and X.Y.: Funding acquisition; W.Z., J.L., and X.Y.: Conceptualization; M.L. and Z.L.: Investigation; X.D., M.L., Y.W., and Y.T.: Data curation; W.Z., B.D., and X.Y.: Manuscript writing, reviewing, and editing; and Z.L.: Data analysis.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the Chongqing Modern Agricultural Industry Technology System (COMAITS202301), the Chinese Academy of Agricultural Sciences “Introduction, Excavation and Innovative Utilization of High-quality Rice Resources”, the earmarked fund for the China Agriculture Research System (CARS–01–25), the National Key Research and Development Program of China (2023YFD2301903), the National Natural Science Foundation of China (31701382), and the strategic cooperation project of the Chongqing Municipal People's Government.

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