| With dwarf sorghum hybrid Liaoza 35, suitable for mechanized production, as the main test material, three planting densities of 90000 plant-ha-1,120000 plant·ha-1 and 150000 plant·ha-1 as the treatments with the medium-high sorghum hybrid Liaoza19 as the control in the planting density of 105000 plan·ha-1 were designed to explore dwarf sorghum photosynthetic characteristics, dry matter production and distribution,yield and its components, for providing a theoretical basis for the dwarf sorghum yield planting techniques. The main results were as follows:1.Dwarf sorghum Liaoza35 different densities,exhibited different photosynthetic characteristics:with the increasing of planting densities,sorghum plant height increased, while stem diameter tapering; in the upper, the middle, the bottom part of leaf angles, within the same canopy leaf level, with the density increasing, the LOV, the leaf inclination showed an increasing trend, with the decreasing of the canopy, the leaf angle is also an increasing trend, the high-density treatment are more obvious,compared with Liaozal9, it showed a significantly difference.2.Dwarf sorghum Liaoza35 in different density treatment groups showed that different abilities to use sun’s energy, which resulted in the different groups of photosynthetic characteristics:with the increasing of planting density in the lower part of the canopy, light intensity and light transmittance significantly reduced, the leaves of the upper canopy was not significant; while in the same growing season, leaf area index increased as the planting density increasing, tended to increase to the maximum in flowering period, then decreased. The treatment of 150000 plant·ha-1 declined faster, group LAD showed the same change trend, the total LAD shown the rise trend; Photosynthetic characteristics from the point of view, with the increase of planting density, canopy photosynthetic rate and stomatal conductance of the lower leaves showed a significantly decreasing trend, while intercellular CO2 concentration showed a gradually rising trend, the difference of index leaf of upper canopy was not significant. During every growth stage, in the upper, the middle, the bottom of the plant canopy, with the planting density increasing, chlorophyll content(SPAD value) showed that lower, the treatment of 150000plant·ha-1 and other treatments were significant differences and since the upper, the middle and the bottom part of the leaves is withdrawn at different times, the aging time is not the same, so the chlorophyll content of each canopy decreased in different stages, were the filling stage, flowering stage, flag leaf stage. With the increasing of planting density, rETR, qP, Fv/Fm of sorghum leaves had a decreasing tread, while Fo showed an increasing tread.3.Dwarf sorghum Liaoza35, different planting densities, the plant dry matter accumulation and distribution are also different. With the increasing of planting density, the sorghum dry matter accumulation per plant showed a decreasing trend, while the population dry matter accumulation was significantly increased. Among all the different densities, leaf assimilates transfer the most to the amount of grain, the average transfer amount is 7.1g per plant. The transfer rate of sheath to the grains with an average of 13.6%is the largest. The contribution rate of leaves was an average of 9.8%, followed by the stem, an average of 6.5%, the sheath was the smallest, an average of 3.5%. The population growth rate gradually increased as the density increasing, especially in the flowering stage, the differences was most obvious. With the increasing of planting density, dry matter stored before anthesis increased, the transfer amount and the contribution rate of Liaozal9’stem were more than Liaoza35’s each treatment, transporters and the amount of Liaozal9’s leaf are similar to Liaoza35’s, but slightly lower than the contribution rate of Liaoza35"s leaves.4.Different densities of sorghum field microclimate groups also had some differences. In the plant canopy, as the density increases, in the upper canopy, CO2 concentration, wind speed had no significantly difference, in the middle of the canopy, the CO2 concentration decreased as the density increased, while the wind speed decreased as the planting density increased. In the bottom of the canopy, the CO2 concentration increased while the planting increased, while the wind speed is no difference.5.With the increasing of planting density, economic yield and biomass of the sorghum Liaoza35 showed an increasing trend, but grain number per spike showed a decreasing trend, while the 1000-grain weight was no difference. The economic yield of Liaoza35 was the highest when planting density’reached 150000 plant ha-1, it reached 9923.5kg ha-1... |
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