| In order to select the suitable sowing dates of Brassica pekinensisin in high altitude cold area at Tian Zhu county,Two different altitude experiment sites were selected,Six sowing date treatments were designed at both sites,sowing seed on April 25,May 2,May 9,May 16,May 23 and May 30.during the effects of different sowing dates on Brassica pekinensisin growth,leaf photosynthesis,physiological characteristics,the yield and quality of Brassica pekinensisin were studied in the experiment using field experiments.The following conclusions were obtained:1.Two different altitude trials of Brassica pekinensisin in 6 sowing dates can be normal growth;With the delay of the sowing date,the growth period of Brassica pekinensisin gradually shortened,T1 is the longest in,T6 is the shortest;plant height is showed late sowing treatment was better than early sowing,Plant vertical projection area and root length have the same trend,the results showed that the late sowing treatment was better than early sowing in the whole growth period.2.With the delay of sowing date,leaf chlorophyll content,POD,SOD and CAT showed the trend of increasing first and then decreasing,and the content of MDA increased first and then increased.The activity of root activity and free proline increased gradually.3.In the rosette stage,the leaf Pn,Gs,Tr,Fv / Fm,ФPSⅡ,q P gradually increased with the delay of sowing date,and the Ci and NPQ of the leaves showed the trend of decreasing first and then increasing,the late sowing treatment of photosynthes is best.4.With the delay of sowing date,fresh weight,root / shoot ratio,dry matter accumulation and dry matter accumulation rate increased first and then decreased,and the maximum amount of dry matter accumulation occurred in advance.5.with the delay of sowing date,yield showed first increase and then decrease,both sites respectively reached the maximum in T3、T4;vitamin C content of both places respectively reached the maximum in T3、T4;nitrate content of T4 was significantly lower than other treatments,209.32 mg/kg and 247.69 mg/kg. |
