Remobilization of dry matter and nitrogen in maize as affected by hybrid maturity class

The length of the growing cycle is one of the most important traits determining hybrid adaptability to the environment. The objective of this research was to compare in a field trial the pattern of dry matter and nitrogen accumulation and remobilization of four commercial maize hybrids belonging to FAO maturity group 400, 500, 600 and 700. The duration of the periods emergence-silking and silking-physiological maturity increased with the increase of hybrid maturity class. Silking occurred 6 days later in the latest maturing hybrid than in the earliest one, and physiological maturity 21 days later. Hybrids differed for biomass production at silking and at physiological maturity. At silking, plant dry weight and leaf area increased with hybrid maturity, owing to greater leaves and stalks. The lengthening of the period emergence-silking allowed a greater accumulation of assimilates in the plant, thus increasing the source of remobilization in the following period. The increase of the length of the period silking-maturity from hybrid 400 to hybrid 700 brought to an increase of dry matter accumulation coupled to a reduction of dry matter remobilization. Increases in hybrid maturity class resulted also in an increase of post-silking N uptakeand N remobilization from vegetative plant parts. Thus, the longer period silking-maturity was associated with an increased photosynthetic activity of the plant, which hampered the rate of leaf senescence and deterred the mobilization of reserve carbohydrates for grain filling. Conversely, the longer was the hybrid cycle, the greater was the quantity of both N uptake from soil and remobilized N from vegetative plant part