Tiller growth and mortality in winter wheat as affected by carbon and nitrogen partitioning via stem internode structure

Context

Tiller growth and development are crucial determinants of grain yields in wheat (Triticum aestivum L.). However, the impacts of tiller internode structures associated with carbon (C) and nitrogen (N) partitioning underlying tiller development and the ultimate yield have not yet been fully elucidated.

Objective

To investigate the tiller internode structure in association with C and N partitioning between stems and their impacts on tiller growth and mortality and the ultimate yield.

Methods

Two wheat cultivars with moderate-tillering (ZM578) and high-tillering (LY502) were grown under field conditions with zero N (N0) and 200 kg N ha⁻¹ (N200). Wheat tillering, C and N partitioning, and the anatomical structures of tiller internodes were investigated.

Results

Compared to the N200 supply, N0 suppressed tillering by 46.8 % in ZM578 at the jointing stage and by 34.7 % in LY502, indicating a more pronounced tillering response to N availability in the moderate-tillering cultivar. However, at maturity, ZM578 achieved comparable spike numbers and grain yields relative to LY502. This can be attributed to the 11.8–22.5 % lower tiller mortality rate in ZM578, which strongly depended upon the maximum tiller numbers rather than N availability. Although comparable or even lower leaf area and SPAD readings were observed, ZM578 exhibited higher photosynthetic rates compared to LY502. Moreover, ZM578 allocated a greater proportion of assimilates to the main stem and superior tillers, resulting in larger assimilate accumulation gaps between the main stem and tillers. In parallel with these findings, ZM578 displayed larger vascular bundle and phloem sizes, particularly under N-deficient conditions, primarily due to larger size of individual vascular bundle and phloem. Likewise, assimilate partitioning to late-generated tillers in ZM578 was lower than that in LY502, indicating a reduction in unnecessary assimilate consumption.

Conclusion

Tiller internode structure plays a significant role in C and N partitioning, which in turn influences tiller development and the ultimate yield.

Implications

The results are informative for creating high-yielding wheat populations through the selection of moderate-tillering cultivars and optimized N management.