Effects of row orientations and planting patterns on senescence of maize leaves at later growth stage

The maize yield mainly comes from photosynthate accumulation after tasseling, while the photosynthetic and physiological characteristics of maize leaf directly affects grain filling; thus, premature aging of functional leaf is one of the important factors affecting maize yield.An appropriate change of row orientation and planting pattern could optimize the canopy structure to improve the light condition within the canopy, and effectively extend green period of maize leaf and increase maize yield.We conducted a field experiment in Jilin Province with 2×2 treatments:2 row orientations, east-to-west orientation (EW) and northeast-to-southwest orientation (SW20), where the orientation was southwestern 20°; 2 planting patterns, ‘65+65’ with 65 cm of both rows (65) and ‘160+40’ with 40 cm of narrow row and 160 cm of wide row.Then, we investigated, during grain filling period, the effect of row orientation and planting pattern on SPAD value, nitrogen content, superoxide dismutase (SOD) and peroxydase (POD) activity of leaves at different leaf positions(leaves above ear leaf, ear leaf and leaves below ear leaf).The results showed that SPAD value with lower and ear leaves during the early filling stage and upper leaf during the later filling stage were higher in SW20 than that in EW.Nitrogen content with different leaf positions was higher in SW20 than that in EW.As for SW20, nitrogen content with lower and upper leaves in ‘160+40’ row was significantly higher than that in ‘65+65’ row.As for east-to-west orientation, SOD activity with ear and upper leaves in ‘160+40’ row was higher than that in ‘65+65’ row.Compared with traditional planting pattern, treatments with 160 cm+40 cm row delayed the aging time of maize leaves and significantly slowed leaf aging speed.