Baiyan Wang Shenghao Gu Juan Wang ^* Guangtao Wang ^* Xinyu Guo ^* Chunjiang Zhao ^*

• Beijing Academy of Agricultural and Forestry Sciences, Beijing, China

The formation of yield and quality in maize involves the accumulation of substances such as starch, proteins, and fats, which interact with water within the kernel. Although temporal dynamics of grain moisture and its functional and environmental determinants have been broadly demonstrated, we still do not have a comprehensive understanding of the distribution of water phase within a kernel. We investigated the relationship between tissue structural traits, including embryo volume (EMBV), endosperm volume (ENDV), vitreous endosperm volume (VEV), floury endosperm volume (FEV), and water content in different phases, such as bound water, semi-bound water, and free water, in maize kernels under different cultivars, nitrogen application rates, and soaking durations by combing low-field nuclear magnetic resonance (LF-NMR) and X-ray microcomputed tomography (μ-CT) for kernels. The results demonstrates that bound water is major phase (57-82%) in maize kernel, and this proportion decreases with prolonged soaking duration. The bound water content and semi-bound water content positively correlate to ENDV, VEV, and EMBV, whereas free water content to ENDV, EMBV, and VEV in the descending order of correlation coefficient. This indicates that water might penetrate embryo through pedicel and vitreous endosperm through pericarp during soaking. Finally, we suggested that the proportion of semibound water could be a robust indicator to predict moisture content in maize kernel. The study provides a preliminary understanding of the structural basis of water distribution in maize kernels, thereby opening up the potential for designing efficient production systems and breeding cultivars well-suited for mechanical harvesting.