| In this paper, field experiments were carried out to evaluate the effects of row spacing and planting density on canopy structure, its microclimate, carbon-nitrogen metabolism and yield in two spike-type winter wheat cultivars (large-spike cultivar Lankao Aizao 8 and multi-spike cultivar Yumai 49, which were widely used in Henan province.) for two growth seasons (2005~2007). The main results were as follows:1 Effects of row spacing and planting density on canopy structure and ray radiation characteristics were studied. The results showed that leaf area index (LAI) for two cultivars presented a single-peak curve during growth stages, and the peak value appeared at booting stage. LAI under different row spacings showed that R2>R1>R3 for Lankao Aizao 8, and for Yumai 49, LAI appeared R3>R2>R1 before middle-filling stages and then there were no distinct differences between row spacings. Mean leaf inclination angle (MLIA) for two cultivars increased with increased planting density and row spacing. At middle-filling stages, Transmission coefficient for radiation penetration (TCRP) for Lankao Aizao 8 decreased with increased density and decreased row spacing, and that for Yumai 49 had no obvious laws in different row spacing and density. Extinct coefficient (K) for tow cultivars rose with larger zenith angle and density, but with increased row spacing, K would decrease. Leaf distribution (LD) for two cultivars became high then low with larger zenith angle. The value for max-min of R2D3 treatment was the smallest for Lankao Aizao 8, and R3D1 treatment for Yumai 49. All in all, canopy structure presented better and leaf distribution showed even for treatment R2D3 to Lankao Aizao 8, and R3D1 for Yumai 49.2 Stalk thickness, mechanics strength, lodging resistant index, vascular numbers and area for two wheat cultivars showed that Lankao Aizao 8 >Yumai 49. Stalk morphological structure of Lankao Aizao 8 displayed better for row spacing R2. Stalk thickness, lodging resistant index, vascular numbers and area, cell wall thickness for Yumai 49 were better for row spacing R3; stalk and cell wall thickness, mechanics cell layers showed better for R3 in low density and for R2 in high density.3 Under the condition of two different densities, the effects of row spacing in two spike-type winter wheat cultivars on canopy microclimate in later growth stages were studied. The results showed that light vertical distribution became more uneven with increased planting density and row spacing. Narrow row spacing population had higher interception (LI) than wide row spacing population. Canopy temperature in vertical way for two cultivars appeared low in upper and lower levels and high in middle level. With larger row spacing, canopy temperature increased. Canopy relative humidity for two cultivars in vertical way would increase from upper level to lower level. With increased row spacing, canopy relative humidity decreased. Carbon dioxide concentration in vertical way showed that lower level > upper level>middle level, and canopy CO2 concentration increased with larger row spacing.4 The activities of SS and SPS in flag leaves for two cultivars presented a single-peak curve during grain filling ( the peak value for Lankao Aizao 8 appeared at 14 days after anthesis, and that for Yumai 49 at 7 days after anthesis). Changes of soluble sugar content in flag leaves for Lankao Aizao 8 presented also a single-peak curve, and the peak value at 28 days after anthesis. And that for Yumai 49 appeared a double-peak curve, and the peak value at 7 and 21 days after anthesis. Contents of soluble sugar and sucrose in grain for two cultivars decreased during days after anthesis. Starch content for two cultivars appeared the trend of"S"type during grain filling. There was an effect of row spacing on sucrose metabolism for two cultivars. SS activity in flag leaves for two cultivars reached the maximum in row spacing R2. SPS activity in flag leaves for two cultivars reached the maximum in row spacing R3 in low density and for R2 in middle-high density. The soluble sugar content in flag leaves reached the maximum in row spacing R3 for Lankao Aizao 8 in high density and for Yumai 49 in low density. The soluble sugar content in grain for Lankao Aizao 8 got the maximum in row spacing R2, and in R3 for Yumai 49 in low-middle density and in R2 for Yumai 49 in high density. Grain starch accumulation for Lankao Aizao 8 showed that R3>R2>R1 in low density, and no distinct difference between row spacing in middle-high density. Grain starch accumulation for Yumai 49 had no distinct difference in low density before 14 days after anthesis, then R3>R2>R1. But in middle-high density, there was no distinct difference among row spacings. 5 Nitrogen content, NR and GS activities in flag leaves for two cultivars decreased during grain filling. Nitrogen content in flag leaves for Lankao Aizao 8 reached the maximum in R1 in low-middle density, and in R2 in high density, and for Yumai 49 it reached the maximum in R1. NR and GS activities in flag leaves after anthesis for two cultivars reached the max in wide row spacing in low-middle density and for narrow row spacing in high density. At maturity, grain protein content for Yumai 49 presented higher than Lankao Aizao 8, and grain protein content for Yumai 49 reached higher in treatment R3D1 and for Lankao Aizao 8 in treatment R1D2.6 Fertile spikelet number and spikelet weight in different spikelet positions for two cultivars showed parabolic changes. And this was accord with medial dominant in grain development. Fertile spikelet number in different spikelet positions for two cultivars decreased with increased planting density. Spikelet weight for Lankao Aizao 8 increased with larger density, and contrary to Lankao Aizao 8 for Yumai 49. Under the same density, fertile spikelet number for two cultivars reached the maximum in row spacing R2, and spikelet weight increased with larger row spacing. Yield for Lankao Aizao 8 reached the maximum for the treatment R2D3 and Yumai 49 for R3D1.According to the result, it was suggested that, to improve grain yield large-spike cultivar Lankao Aizao 8 be planted in narrow row spacing with high density and Yumai 49 in wide row spacing with low density in wheat cultivation.
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