Leaf anatomy, not root anatomy, is related to yield improvement in winter wheat genotypes in a subtropical area of eastern China

Wheat (Triticum aestivum L.) production in the subtropical environment of eastern China plays a critical role in national food security. However, high temperatures and high humidity during the reproductive phase in the region limit wheat growth and yields. We investigated the relationships between anatomical traits in leaves and roots and grain yield to understand the effects of yield improvement on anatomical traits in a hot, wet climate. We selected 20 wheat genotypes that have been widely planted in the past decade in Nantong, Jiangsu, China. We measured yields in the fieldand anatomical traits of seminal roots and flag leaves relevant to carbon allocation and water transport at anthesis. Cross-sectional flag leaf mesophyll area was negatively correlated with yields, but cross-sectional leaf vein area, xylem area of the major vein, and leaf thickness were positively correlated with yield. However, there were no significant associations between yield and root anatomical traits, including cross-sectional seminal root cortex area and xylem area.Yield improvement in eastern China is associated with the increase in leaf vein area, leaf thickness, and vessel size in the major vein, but is not related to the anatomical traits in roots, implying that high-yielding genotypes had increased leaf water transport efficiency and may effectively regulate canopy temperature and maintaingas exchange. These could be key anatomical adaptive strategies to cope with high temperature and highhumidity stress and contribute to yield improvement in the subtropical environment of eastern China.