| In order to investigate the changes and differences of potato’s growth,photosynthetic characteristics,chlorophyll fluorescence characteristics,yield and quality with different plant-row spacing configurations,finally to get potato’s optimum plant-row spacing for high yield and good quality.This experiment based on single cropping condition adopted a randomized design.It was through the different combinations of potato varieties,planting density and the ratio of intrarow spacing to row spacing(IS/RS)to mainly explore the effect of IS/RS on potatoes’ photosynthesis physiology,yield and quality.The main results were as follows:1.Effects of IS/RS on dry matter accumulation above ground of potatoThe dry matter weight of potato’s stems and leaves showed a single peak curve with the advance of growth period,and all treatments reached the peak in tuber expansion stage.The dry matter weight of stems and leaves per plant of Qingshu 9 was higher than that of Favorita in same plant-row spacing.In later growth period,higher density made lower dry matter weight of stems and leaves.IS/RS had little influence on dry matter weight of stems and leaves in tuber initiation stage,but the difference between treatments of each experiment increased with the advance of growth period.The dry matter weight of stems and leaves in general showed a downward parabolic change with the increase of row spacing.Configurations for higher dry matter weight of potato stems and leaves were as follows: Qingshu 9 in 2 500 plants/667 m~2 chose the IS/RS of 1:1(51.7cm×51.7cm)and 1:1.5(42.2 cm×63.3 cm)and in 4 000 plants/667 m~2 chose 1:2(28.9 cm×57.7 cm);Favorita in 4 000 plants/667 m~2 chose the IS/RS of 1:1.5(33.3 cm×50.0 cm)and in 5 000 plants/667 m~2 chose 1:1.5(29.8 cm×44.7 cm)and 1:2(25.8 cm×51.7 cm).2.Effects of IS/RS on LAI and chlorophyll of potatoDuring the growth period,LAI of potato increased first and then decreased,and all treatments reached the maximum in tuber expansion stage.In the same plant-row spacing,Qingshu 9’s LAI was higher than Favorita’s.Within a certain range,LAI increased with the increase of density,and LAI in higher density decreased more than lower density’s in later stages of growth.IS/RS made little effect on LAI in tuber initiation stage but a significant impact in tuber expansion stage and starch accumulation stage.The LAI of this two periods showed a downward parabolic change with the increase of row spacing.Generally considering,the configurations for higher LAI were as follows:Qingshu 9 in 2 500 plants/667 m~2 chose the IS/RS of 1:1(40.8 cm×40.8 cm),in 4 000 plants/667 m~2 chose 1:2(28.9 cm×57.7 cm)and 1:2.5(25.8 cm×64.4 cm);Favorita in 4 000 plants/667 m~2 chose the IS/RS of 1:1.5(33.3 cm×50.0 cm),in 5 000 plants/667 m~2 chose 1:1.5(29.8 cm×44.7 cm)and 1:2(25.8 cm×51.7 cm).From tuber initiation stage to starch accumulation stage,the chlorophyll content decreased firstly and then increased slightly,all the treatments reached the highest chlorophyll content in tuber initiation stage.Qingshu 9’s chlorophyll content was higher than that of Favorita under same plant-row spacing.For the same cultivar,the content of chlorophyll in high density was slightly higher in early stage,little difference with lower density’s in medium stage and lower in later stage.IS/RS had a significant impact on chlorophyll content.Each experiment showed a different change in tuber initiation stage,but the content of chlorophyll in tuber expansion stage and starch accumulation stage was tend to a downward parabolic change or a gradual decline.In the middle and late growth period of potato,the configurations for higher chlorophyll content were as follows:Qingshu 9 in 2 500 plants/667 m~2 chose the IS/RS of 1:1(40.8 cm×40.8 cm)and 1:1.5(42.2 cm×63.3 cm),in 4 000 plants/667 m~2 chose 1:2(28.9 cm×57.7 cm)and 1:2.5(25.8 cm×64.4 cm);Favorita in 4 000 plants/667 m~2 chose the IS/RS of 1:1.5(33.3 cm×50.0 cm),in 5 000 plants/667 m~2 chose 1:2(25.8 cm×51.7 cm).3.Effects of IS/RS on photosynthetic parameters of potatoWith the advance of potato growth period,Pn,Gs and Tr decreased,Ci increased.In same plant-row spacing,Qingshu 9’ photosynthetic rate was higher than Favorita’s.In later growth period,Pn,Gs and Tr in higher density were slightly lower but Ci slightly higher.IS/RS had a significant impact on Pn,Gs,Tr and Ci.Pn,Gs and Tr were tend to a downward parabolic change or a gradual decline with the increase of row spacing,the change of Ci was contrary to theirs.Significant positive correlations were found between Pn,Tr and Gs and they all negatively correlated with Ci.4.Effects of IS/RS on chlorophyll fluorescence parameters of potatoWith the advance of growth period,Fv/Fm,Y(II)and qP decreased and NPQ increased.Compared with Favorita,Qingshu 9 had higher Fv/Fm,Y(II)and NPQ and lower qP in the same plant-row spacing.Y(II),qP in high density was lower than that of low density,and NPQ was higher.Planting density and IS/RS had little influence on Fv/Fm but significant impacts on Y(II),qP and NPQ.Y(II)and qP showed a downward parabolic change with the increase of row spacing in general,NPQ was contrary to theirs.There was a not significant positive correlation between Y(II)and Fv/Fm,and Y(II)was positively correlated with qP.These three were all negatively correlated with NPQ.5.Effects of IS/RS on yield of potato and commodity potato rateThe commodity potato rate of Favorita was higher than Qingshu 9’s in same plant-row spcing,higher density caused lower commodity potato rate.The effect of row spacing on commodity potato rate decreased with the increase of density,and the commodity potato rate increased with the increase of the row spacing under lower density.Qingshu 9’s yield was higher than that of Favorita under a same field configuration.Within a certain range,yield of potato increased with the increase of planting density.IS/RS had a significant impact on potato’s yield,IS/RS showed greater influence on Qingshu 9’s yield than Favorita’s,the yield showed a downward parabolic change with the increase of row spacing.Qingshu 9 in the density of 2 500 plants/667 m~2 obtained the highest yield with the IS/RS of 1:1.5(42.2 cm×63.3 cm),it reached 3 134.92 kg/667 m~2 and it was significantly higher than others’.Qingshu 9 in 4000 plants/667 m~2 got the highest yield with the IS/RS of 1:2.5(25.8cm×64.6cm),it reached 4034.82 kg/667 m~2 and it was significantly higher than others’.Favorita in 4 000 plants/667 m~2 got the highest yield with the IS/RS of 1:1.5(33.3 cm×50.0 cm),it reached 2 252.22 kg/667 m~2 and had little difference with the IS/RS of 1:1(40.8 cm×40.8 cm).Under the density of 5 000 plants/667 m~2,Favorita’s IS/RS of 1:1.5(29.8 cm×44.7 cm)obtained the highest yield,it was 2 358.89 kg/667 m~2.Compared with the treatment in IS/RS of 1:2(25.8 cm×51.7 cm),which obtained 2 351.90 kg/667 m~2,the yield in IS/RS of 1:1.5 had no significant difference with the yield in IS/RS of 1:2,but they were significantly higher than others’.6.Correlations between potato yield and photosynthetic physiology indicatorsThe yield of potato had positive correlations with LAI,Chla+Chlb,Pn,Tr,Gs,Fv/Fm,Y(II)and qP.Other positive correlations were found between Chla+Chlb,Pn,Tr,Gs,Fv/Fm,Y(II)and qP,it showed that light energy absorption,conversion and photosynthetic carbon assimilation were closely combined and influenced each other.They greatly affected the formation of potato’s yield.7.Effects of IS/RS on tuber quality of potatoVariety was the main determinants of potato quality,Qingshu 9’s content of starch,vitamin C,soluble protein,reducing sugar and dry matter weight of tuber were higher than that of Favorita.The dry matter weight of tuber had a not significant positive correlation with soluble protein content,but significant positive correlations with starch content and vitamin C content and a not significant negative correlation with reducing sugar content.Starch,vitamin C and soluble protein were positively correlated.The effect of density on potato’s quality varied with density range and variety.The contents of dry matter weight of tuber,starch,soluble protein,vitamin C and reducing sugar in the range increased with the increase of density.The results showed that the dry matter weight of tuber,starch content,vitamin C content and soluble protein content were changed to the parabola with the increase of row spacing,and the content of reducing sugar was tend to an upward parabola.Optimum configuration for better quality of potato(ie,higher content of tuber dry matter,starch content,vitamin C content,soluble protein content and lower reducing sugar content)were as follow: Qingshu 9 under the density of 2500 plants/667 m~2 chose the IS/RS of 1:1.5(42.2cm×63.3cm),in 4000 plants/667 m~2 chose the IS/RS of 1:2.5(25.8cm×64.6cm);Favorita in 4000 plants/667 m~2 and 5000 plants/667 m~2 both chose the IS/RS of 1:1.5,represented plant-row spacing 33.3cm×50.0cm and 29.8cm×44.7cm respectively.8.Potatoes’ optimum plant-row spacing for higher yield and better qualityHigher yield and better quality configurations of potato were as follows: Qingshu 9 in 2 500 plants/667 m~2 selected the IS/RS of 1:1.5(42.2 cm×63.3 cm),the IS/RS of 1:2.5(25.8 cm×64.6 cm)for 4 000 plants/667 m~2;Favorita in 4 000 plants/667 m~2 selected the IS/RS of 1:1.5(33.3 cm×50.0 cm),the IS/RS of 1:1.5(29.8 cm×44.7 cm)for 5 000 plants/667 m~2.The best treatments for two varieties were that Qingshu 9 under 4 000 plants/667 m~2 chose IS/RS of 1:2.5 and Favorita under 5 000 plants/667 m~2 chose IS/RS of 1:1.5. |
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