The Research On The Relationship Between The Group Light Distribution, The Stem Morphological Characteristics, Anatomical Structure And Lodging-resistance Of Different Density-tolerant Varieties Of Maize

Xinjiang is the region of the most high-yield records of maize in China. In recent years, thereare some places like Yili and Qitai which have continuously created high-yield records.However, lodging is the main reason for the maize production decreasing in Xinjiang.Generally, we attribute field shade canopy closure increasing, light and nutrient fiercecompetition among the plants to maize planting density increased. This paper directed atproblems such as change of plant stem morphology and lodging increase leading by plantingdensity increased. In this experiment, I applied resistance of different density-tolerantvarieties of maize as materials and set three planting densities: low-density, medium-densityand high-density; aiming at studying the characteristics of canopy structure, thephotosynthetic characteristics and dry matter accumulation of different cultivars; analysingthe relationship between the stem morphology characteristics and the stem mechanicalcharacteristics; clarifing the influence of different planting densities on the formation of thestem morphological structure and the stem strength, field lodging rate, yield and itscomposition factors in the maize prone to lodging. The results revealed the mechanism ofhigh yield and resistant lodging of different density-tolerant varieties of maize under theecological conditions of Xinjiang and provided the theory basis of maize high yieldcultivation and dense planting technology to increase production for Xinjiang. The mainresults were as follows:1. The impact of different planting densities on the light transmittance at the bottom of thecanopy and leaf area indexIn the whole growth period, light transmittance at the bottom of the canopy of the testingvarieties decreased with increasing planting density, but the leaf area index had the oppositeregulation. The canopy structure built step by step following with vegetative organs of rapidgrowth from elongation stage to tasseling stage. The reduction of light transmittance at thebottom of the canopy was large from the elongation stage to the big bellbottom stage, whilesmall from the big bellbottom stage to the tasseling stage. The canopy structure of ZD909wasbetter than XY41. While the leaf area index was close to4, the reduction of lighttransmittance at the bottom of the canopy was smaller; as it reached6, the LAI declinedaccelerate for the canopy was too large causing the lower light worse. Light transmittance atthe bottom of the canopy and the LAI presented decline trend of exponential function, andthey reached the extremely significant negative correlation.2. The impact of different planting densities on the plant morphological characteristics andanatomical structurePlant height, ear height, center of gravity height and internode length of the testingvarieties all increased with increasing planting density, while internode diameter decreased.The plant type structure of ZD909was better than XY41. Thickness of mechanical tissue, mechanical cell layers and cortical thickness/radius of stem decreased in the internal structure,as the change of the density of vascular bundle along with the planting density was stronglyinfluenced by internode diameter and the change rules performed inconsistent beforeflowering and after it. The degree of internodes cortex mechanization of ZD909was betterthan XY41. Density treatments had large effects on plant morphological structure. While itless affected by the interactions of density and culture.3. The impact of different planting densities on the stem strengthMechanical indicators of the testing varieties all decreased with increasing plantingdensity, and decreased with the increase of internodes section, and increased with the passageof growth period. All the mechanical indexes of each internode of ZD909were greater thanXY41. Light transmittance at the bottom of the canopy and the stem strength of basalinternode and ear position internode had positive correlation. All the indicators in plantmorphological structure had correlation with the stem strength.4. The impact of different planting densities on the lodging resistanceThe field lodging rate of the testing varieties increased with increasing planting density.The field lodging rate of ZD909was smaller than XY41under the various density treatments.ZD909was toleranter to density and lodging than XY41. Density treatments and cultures hadlarge effects on lodging rate. While it less affected by the interactions of density and culture.5. The relationship of plant morphological structure, the stem strength and lodging ratePlant height, center of the gravity height and ear internode length had positive correlationwith the field lodging rate; while internode diameter, thickness of mechanical tissue,mechanical cell layers, and densitiy of vascular bundle and cortical thickness/radius of stemhad negative correlation with the field lodging rate. The stem strength and lodging rate had anegative correlation and the relevant degree had associate with different growth periods andinternode positions.6. The impact of different planting densities on dry matter accumulation and yieldDry matter accumulation and reproductive organs of the testing varieties increased withincreasing planting density, while full production capacity had the same trend. In thecomposition of production factors, the number of ears increased with increasing plantingdensity, while grain numbers per ear and one thousand seed weight decreased. The yieldpotential of ZD909was better than XY41. When the optimum density of ZD909was9～10.5×10~4plants/ha, its yield would reach13948～14883kg/ha. While the optimum density ofXY41was7.5～9×10~4plants/ha, its yield was11969～12491kg/ha. The affect of the densityand culture on the yield were greater than the interactions of them.