Structural volume composition of internodes determines culm non-structural carbohydrates accumulation in rice

Abstract

Abstract Non-structural carbohydrates (NSC) stored in the stem play a crucial role in supporting yield formation in rice. However, internode morphological determinants of NSC accumulation are 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. Manipulation of internode development using plant growth regulators demonstrated that altering VCR effectively modified 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 NSC accumulation to achieve high and stable yield performance in rice.

Plant phenotyping relevance

イネ茎の形態からNSC蓄積能を評価する新規指標VCRを導入し、再現性と既存形態形質との比較まで行っており、表現型評価法が研究の中心である。

Code and data availability

The preprint describes field/pot phenotyping of rice internode morphology and NSC content, but no blocks contain any public phenotype dataset deposit, image/sensor data release, or author analysis code with an explicit availability statement or public URL. Supplementary files are summary tables/figures hosted on the (c

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