| In order to select the optimum ionic strength of nutrient solution,light quality,formula of GA+6-BA and cutting times,as well as promoting the propagation coefficient of cutting seedlings and micro-tubers.This experiment was carried out in 2014-2016,using three potato varieties of ?Yushu No.1‘,Favorita and ?E`shu No.5‘.It was mainly studied on the differences of virus-free potatoes‘ plant growth,photosynthetic characteristics and chlorophyll fluorescence characteristics and the tuberization and reproduction of cutting seedlings in different light qualities,ionic concentration of nutrient solution,phytohormones and treatment of cut stem.We got the results as follows: 1.The optimum ionic concentration of nutrient solution of potato by hydroponic.The best ionic concentration of nutrient solution for both ?Yushu No.1‘ and ?E`shu No.5‘ was 3186.38 mg L-1（EC=2.91 MS cm-1）in the whole period,it obtained the highest number and production of micro-tuber per plant;during tuber bulking stage,root activity,net photosynthetic rate（Pn）,maximal photochemical efficiency（Fv/Fm）,actual photochemical efficiency（ΦPSⅡ）,electron transport rate（ETR）and photochemical quenching（qP）of this treatment all increased;high ironic concentration of 4248.51 mg L-1 promoted vegetative growth and chlorophyllous synthesis,in addition,increased the number of stolons per plant.While it inhibited tuber‘s initiation and delayed the stage of tuber formation.Low concentration of nutrient solution(C≤2124.26 mg L-1)improved the potato rate but significantly decreased leaf area per plant,root activity,Pn,Fv /Fm,ΦPSⅡ,ETR,qP and the number of stolons per plant,finally led to lower production.The ionic concentration‘ reduction in vegetative growth period and increase during tuber expansion stage was a key method to raise the yield of micro-tuber in hydroponic culture.2.The most reasonable LED light quality for potatoes‘ growth and tuberization.The 5Red+1Blue treatment got the best tuber weight per plant and 7 Red+1Blue treatment had the largest number of micro-tuber per plant.They both resulted in higher leaf area index,chlorophyll content,stomatal density and Gs;they also remarkably improved Pn,ΦPSII,qP and ETR and led to earlier tuberization compared with white light treatment.However,the contents of chlorophyll,Pn and ΦPSII decreased quickly on the 60 th day.It matured ahead of time with less stolon,and reached the best micro-tuber yield and potato rate.Those treatments under red light reduced the leaf area index,chlorophyll content,Gs,Pn,Fv/Fo,ΦPSII and qP,increased NPQ,slowed down tuber formation and led to the lowest yield.Furthermore,those treatments under blue light inhibited the formation of stolon and limited the number of micro-tuber per plant.The analysis indicated that higher proportion of red light could promote the formation of stolon;while higher proportion of blue light would promote the tuber formation and expans ion,shortened the production cycle.Basing on these results,in terms of light adjustment,it was advisable to increase the proportion of red light in the earlier stage to induce the formation of stolon,and increase the blue light‘s proportion in the later period to promote the formation and expansion of tuber,increase the number of tuber and final yield.3.The best formula of GA+6-BA and most suitable cutting times on reproduction of tuber and seedlingCutting treatment could promote the branching and expand the multiplication of the cutting seedlings.However,the treatment of cutting not only had a negative effects on the yield of micro-tuber,but also seriously affected the growth of potato plants after the first cutting.Concretely,it significantly decreased the leaf area,the dry matter weight of whole plant,the rate of stolons formation and micro-tuber‘s yield.The overall multiplication rate increased with the increase of the number of cuttings,it got the highest multiplication rate at third time.The maximum concentration of gibberellin applied to the leaves was 15 mg·L-1,otherwise,it would decrease final yield and caused lower number of cutting seedlings and worse quality.6-BA directly sprayed on the leaves would lead to premature senescence of stems and leaves.The addition of 6-BA in GA favored the underground material‘s accumulation.The relative concentrations of exogenous GA and 6-BA could regulate cutting seedlings‘ propagation and tubers growth of potato.The formula of GA 20 mg·L-1 + 6-BA 1.5mg·L-1 had the best number of branches;the treatment of GA 20 mg·L-1 + 6-BA 0.5 mg·L-1 had the best effect on cutting dispose.Increasing the concentration of 6-BA in mixed phytohormones significantly slowed the elongation of branches and reduced the number of cutting seedlings,but decreased the promotion of GA to stolons and promoted the formation of tubers.The foliar application of GA 10mg·L-1 or GA 20 mg·L-1+6-BA 0.5 mg·L-1 could significantly increase the yield of micro-tuber.The high concentration of 6-BA promoted the expansion of micro-potato but inhibited the stolon formation,and ultimately limited the tuber yield.The four formulas of phytohormones were significantly better than the blank control,and the highest propagation coefficient（both the quantity of micro-tubers and cutting seedlings）was got in the formula of GA 20 mg·L-1 + 6-BA 0.5 mg·L-1.The two factors interaction between cutting times and phytohormones significantly affected the reproduction of seedling-tuber.（1）The highest yield of micro-tuber was obtained under non cutting treatment and along with 10 mg·L-1 GA or GA 20 mg·L-1 + 6-BA 0.5 mg·L-1;（2）Cutting seedlings for 3 times with GA 20 mg·L-1 + 6-BA 0.5 mg·L-1 got the best effect of cutting seedlings and reached the highest total seedling multiplication.In the actual production,it was suggested to choose a more reasonable number of cutting times and phytohormones formulas based on production purpose. |
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