Effects Of Row Direction And Row Spacing On Leaf Sene-scence In Maize

Appropriate planting methods can effectively extend leaf holding period and increase maize yield.By changing row direction and planting pattern,canopy structure can be optimized and maize canopy lighting conditions can be improved,thereby increasing maize yield.Southwestern 20°‘160 + 40’ changed plant field configuration by different row orientations and planting patterns,optimizing population structure and improving microenvironment such as illumination,temperature,humidity and CO2 in population.It may affect the growth and function of maize leaves,which will slow down the aging of maize to a certain extent.The previous which studies individually on row orientation or row spacing had a greater impact on the senescence of maize leaves.But considering row direction and row spacing comprehensively,the impact on the senescence of maize leaves was less studied.This paper takes maize as the research object,using field test(regional contrast)to analyze three row orientations(south-north,east-west,southwestern 20°)and two row spacing(‘65 + 65’,‘160 + 40’).To reveal regularity of senescence and development of maize leaf,as well as clarify physiological and ecological mechanism,we investigated the effect of row orientation and planting pattern on occurrence and development,as well as photosynthetic performance,physiological and biochemical indicators related to the aging of leaves.Concluded as follow:(1)‘160 + 40’ effectively extended the growth period in the upper and middle leaves of maize,enhancing the lodging resistance of maize and delaying the decay rate of leaf area after flowering.Southwestern 20°can extend the green period of leaves,effectively increasing the leaf area,leaf area index and specific leaf weight of ear leaf after flowering in maize.Southwestern 20°‘160 + 40’ is conducive to prolonging the green period and photosynthesis time of ear leaf.Planting direction had no significant effect on the plant height of maize.Both planting direction and the row spacing had no significant effect on the specific leaf weight of maize.(2)During mature period,‘65 + 65’ resulted in the increase of Fo values in different parts of maize and the decrease of Fv/Fo and Fv/Fm in lower leaves,resulting in relatively increasing damage to the PSII reaction center,thereby inhibiting photo-synthesis.The light energy conversion efficiency is lower than the 160 cm + 40 cm,which exacerbates photosynthetic inhibition of maize and reduces the potential activity of PSII.During mature period,Southwestern 20°and ‘160 + 40’ significantly increased photosynthetic rate at different parts of maize leaves.Southwestern 20°‘160 + 40’was beneficial to improve the photosynthesis and Fv/Fo of ear leaf after flowering,delaying leaf senescence.During mature period,in south-north and east-west,Fo values of leaves at different positions in ‘65 + 65’ were higher than those of ‘160 + 40’.Fv/Fo values and Fv/Fm values in the upper leaves of ‘160 + 40’were higher than those of ‘65 + 65’.Fv/Fo values of ear leaf after flowering in southwestern 20°‘160 + 40’ is higher than other planting methods.Planting direction had no significant effect on the chlorophyll fluorescence parameters of maize.During mature period,in three different rows,the photosynthetic rate of leaves at different positions in ‘160 + 40’ was higher than ‘65 + 65’ with the order was: southwestern 20°>east-west >north-south.The photosynthetic rate of ear leaf after flowering in southwestern 20°‘160 + 40’ was higher than other planting methods.During mature period,southwestern 20°can maintain higher SPAD values in the upper leaves.Both planting direction and row spacing had no significant effect on chlorophyll content of leaves at different positions.(3)Southwestern 20°,‘160 + 40’ and southwestern 20°‘160 + 40’ can all effectively remove reactive oxygen free radicals,which helps the leaves to accumulate more organic matter and prevent cells from damage,maintaining the integrity of the structure and delaying the aging of the leaves.During the mature stage,the protective enzyme activity and soluble protein content of leaves at different positions in ‘160 + 40’ were higher than ‘65 + 65’ with the order was: southwestern 20°>east-west >north-south.The malondialdehyde content and proline content of leaves at different positions in ‘65 + 65’ were higher than ‘160 + 40’.During the mature stage,the protective enzyme activity,soluble protein content and reducing sugar of leaves at different positions in southwestern 20°‘160 + 40’ were higher than other planting methods.The soluble protein content and reducing sugar in ear leaf after flowering in southwestern 20°‘160 + 40’ was higher than other planting methods,but free amino acid content and malondialdehyde content is opposite.Planting direction had no significant effect on reducing sugar content and total free amino acids in maize leaves.Row spacing had no significant effect on the proline content in maize leaves.(4)During the mature stage,maize yield in ‘160 + 40’ were higher than ‘65 + 65’ with the order was: southwestern 20°> north-south> east-west.The maize yield of southwestern 20°‘160 + 40’ was significantly higher than other planting methods.In summary,southwestern 20°‘160 + 40’ is favorable for prolonging the photosynthesis time of ear leaf,increasing photosynthetic rate,effectively removing the active oxygen free radicals in leaves at different parts of the maize at the mature age,and accumulating more organic matter,preventing cells from damage,maintaining the integrity of the structure,delaying leaf senescence and increasing maize yield.Therefore,in Dehui City,Jilin Province,southwestern 20°‘160 + 40’ delays leaf senescence at the late stage of growth of maize,as well as the effect of increasing maize yield is most obvious.