It has been established that concentrations of greenhouse gases (GHG) such as CH₄, CO₂, and N₂O in the atmosphere have dramatically increased since the beginning of the industrial revolution, primarilybecause of fossil fuel combustion and land use change. Meanwhile, the increased GHG concentrations have led to a rapid rise in global temperature over the past decades.The impacts of future global warming on the structure and function of agricultural ecosystemsmay not only change the carbon balance of terrestrial ecosystems, but also threat the safety of the future global food supply. Maize (Zea mays L.)is one of the most important crops worldwide, and thus maize production determines the safety of the food supply in many regions of the world, includingthe North China Plain, which is an important region of crop production in China.Ithas been predicted that global warming may reduce maize yieldsin this region. However, the underlying mechanisms of the effect of climate change on crop production are not well understood.In particular, the impacts of global warming on the leaf structure, physiology, and biochemistry of crops such as maize plants were previously unknown.In this study, we examined the effects of experimental warming on the morphology, anatomy, ultra-structures, and physiological traits of maize leaves, via a fieldexperiment usinginfrared heaters conducted in a typical agriculture ecosystem on the NorthChina Plain. The warming experiment features six 3×4 m plots, with three of the plots serving as treatments and the others as control plots. In comparison to the control, the warming increased the air, soil, and canopy temperature by(1.42±0.18)/(1.77±0.24)℃ (day/night), (1.68±0.9)/(2.04±0.16)℃ (day/night), and (2.08±0.72)℃(day) during the maize growth period. The results showed that experimental warming significantly decreased the width and thickness of maize leaves by 4% (P=0.017) and 10% (P < 0.001), respectively, but barely affected leaf length. The decreased leaf thickness was mainly due to the decreased mesophyll cell size (mainly palisade tissue)rather than the number of cell layersproduced by maize leaves under warming conditions.Interestingly, experimental warming also significantly reduced the distance between vascular bundles by c.10% and the area of vascular bundle by c.30%, resulting in more and smaller vascular bodies. In contrast, elevated temperature significantly increased the average length and width of chloroplasts by 46% and 50%, respectively, compared to the control. This resulted in a dramatic c.140% increase in the chloroplast profile area. Moreover, experimental warming also increased mitochondrial size by c. 53%. Our results also showed that experimental warming significantly increased net photosynthetic rates (P_n), stomatal conductance (G_s), and transpiration rates (T_r) by 52% (P=0.019), 163% (P=0.001), and 81% (P=0.017), respectively. Meanwhile, experimental warming significantly decreased dark respiration rates in the leaves (R_d) by 24% (P=0.006), but had little effect on intercellular CO₂ concentration (C_i) or water use efficiency (WUE). These results suggest that future climate warming may not only directly change maize morphology and structure, but also influence the biological functions (such as photosynthesis and dark respiration) of maize leaves on the North China Plain. Our results may be of great importance for understanding the mechanisms of the maize response to experimental warming, and thus provide important information for agricultural ecosystem management under future global conditions.