Structural Volume Composition of Internodes is a Key Morphological Factor Contributing to Culm Non-structural Carbohydrate Accumulation in Rice.

Abstract

Non-structural carbohydrates (NSC) stored in the stem play a crucial role in supporting yield formation in rice. However, internode morphological factors associated with NSC accumulation remain unclear. This study aimed to clarify the relationship between internode morphology and NSC accumulation and to identify a robust morphological indicator for evaluating NSC accumulation capacity. Two years of field experiments were conducted using multiple cultivars. The NSC content was quantified for individual internodes and at the whole-plant culm level, and its relationships with internode morphological traits were analyzed. Since the upper internodes (UIN; first and second internodes) and lower internodes (LIN; third and subsequent internodes) exhibited contrasting roles in NSC accumulation, a novel index was introduced, the volume composition ratio (VCR) of UIN/LIN, which represents their relative volumetric contributions within a culm. The VCR of UIN/LIN showed the strongest correlation with culm NSC and high reproducibility across years, outperforming simple morphological traits. In addition, plant growth regulator treatments that altered VCR were accompanied by changes in culm NSC accumulation. Accordingly, the VCR of UIN/LIN serves as a robust morphological indicator of culm NSC accumulation capacity, providing a practical framework for improving stem carbohydrate storage capacity in rice.

Plant phenotyping relevance

イネ茎の形態からNSC蓄積能力を評価する新規指標VCRを導入し、複数年で再現性と既存形態形質との性能を検証しており、形態表現型の抽出・評価法が中心である。

Code and data availability

The manuscript reports field and pot phenotyping of rice internode morphology and NSC accumulation, but no public phenotype dataset, image/sensor inputs, analysis code, or trained model is deposited. The only availability statement says data are within the article and its additional files, which does not constitute a作者

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