| Taking the dominating planted hybrid late supper rice variety’WufengyouT025’as the test material, removal pot of rice were transplanted rice fields after treating immediately. The experiment was designed with two low temperatures (19℃ and 20℃) and 1 to 3 running days, three low temperatures (21℃,22℃ and 23℃) and 2 to 5 running days under low temperature stress at heading and floweingr stage. The natural temperature was taken as the control. Under the condition of low temperature stress pollen vitality, photosynthetic parameters and chlorophyll content (SPAD value) in the second upper leaves and proline content, cell membrane permeability, membrane lipid per-oxidation product malondialdehyde content (MDA) in the flag leaves were measured and then surveyed yield components, using subordinate function has carried on the comprehensive evaluation of yield components, and then determined to the order of chilling injury.Results were as follows:(1) Effects of different treatments on yield and yield components under low temperature stress.The panicle weight of 20℃ 2-3d,21 ℃2-5d,22℃ 4-5d and 23 ℃ 4-5d highly significantly dropped. The 1000-grain weight of 19℃ 3d and 23℃ 5d very significantly reduced. The grain-filling rate of 20℃ 2-3d,21℃ 2-5d,22℃ 2-5d and 23℃ 2-5d highly significant lowered. The seed-setting rate of 19℃ 2-3d,20℃ 2-3d,21℃ 2-5d,22℃ 2-5d and 23 ℃ 2-5d very significant reduced. The empty grain rate of 19℃ 2-3d,20℃ 2-3d,21℃ 2-5d, 22℃ 2-5d and 23℃ 2-5d very significant added. The non-fully filled grain rate of 20℃ 2-3d and 22℃ 3-5d highly significant reduced. Yield components of average subordinate function value were more than 0.3, chilling injury sequence in the order was: 21℃5d>21℃4d>23℃5d>23℃4d>21℃3d>20℃3d>21℃2d>22℃5d>20℃2d>23℃3d>22℃ 4d.(2) Effects of different treatments on physiological indexes under low temperature stress.Low temperature treatments resulted in the reduction of net photosynthesis, stomatal conductance and water use efficiency, whereas increase of intercellular CO2 concentration in the second upper leaves. The changes of photosynthetic parameters of 21℃ 2-5d treatments were more than other treatments. Different treatments of relative chlorophyll content (SPAD value) were greater differences in the second upper leaves. SPAD value of 19℃ 1-3d and 22℃ 2-3d showed a initial rising trend to the downward trend on 0 day after treatment, but SPAD value rapid decreased on 5 days after treatment; the other treatments of SPAD value showed a gradual decrease, and SPAD value rapid reduced on 10 days after treatment. Different treatments of pollen vitality were decreased to varying degrees. The decreasing percentage of pollen vitality in the order was:21℃ 5d=21℃ 4d>21℃ 3d>23℃ 5d>20℃ 3d>22℃ 5d>19℃ 3d>20℃ 2d>22℃ 4d>21℃ 2d>19℃ 2d>23℃ 4d>20℃ 1d>19℃ 1d>22℃ 3d>22℃ 2d>23℃ 3d>23℃ 2d. Different treatments of proline content were some differences in the flag leaves under low temperature stress. There were increase on 0 day after treatment, but the changes of proline content showed differently on 3 and 6 days after treatment. Proline content of 19℃ 1-3d,20℃ 1-3d,22℃ 2-5d and 23℃ 2-5d showed initial rising trend to the downward trend, but proline content of 21℃ 2-5d showed rising trend after treatment. Different treatments of relative electric conductivity and damage rate of the rice flag leaves showed an initial rising trend to the downward trend and increasing trend. Relative electric conductivity and damage rate showed rising on 0 day after treatment, relative electric conductivity of 20℃ 3d,21℃ 2-5d and 23℃ 4-5d highly significantly augmented. Different treatments of MDA content presented up-trend in the rice flag leaves. |
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