Research Of Influence On Relay-cropping Potatoes’Photosynthetic Physiology Characteristics And Yield Caused By Different Spacing And Row Spacing

To investigate efficient utilization principle and production-increasing mechanism of light energy inside relay-cropping groups and enrich the relay-cropping cultivation system of Southwest China, this experiment studied light environment, photosynthetic physiological characteristics, leaves physiological response mechanism under light stress and dry plant tissue accumulation and its influence on yield inside potatoes/maize relay-cropping system through different combinations of small row spacing and spacing of potatoes and small row spacing of maize with sole cropping and a row proportion of2:2. Main findings are as follows:(1) Influence on content of LAI, SLW and chlorophyll of potatoes’photosynthetic leavesStaging measurement on green leaves of potatoes indicated that LAI had a positive correlation with potatoes’small row spacing, namely, the smaller the row spacing and spacing of potatoes were (the bigger the row spacing of maize was), the lower the LAI was. Duo to the shading from maize, the content of SLW, Chla, Chlb, Chla+Chlb in potatoes developed in a trend of augment-reduction, with a peak obtained during the tuber growth period. In this experiment, the LAI of treat1and7, in which field of treat7consisted of40-centimeter-wide small row spacing and60-centimeter-wide spacing of potatoes and20-centimeter-wide small row spacing of maize and that of treat4consisted of20-centimeter-wide small row spacing and60-centimeter-wide spacing of potatoes and40-centimeter-wide small row spacing of maize, has reached over4and treat7kept a high content level of Chlb, which effectively enhanced leaves’ capacity of light energy intercepting and laid a solid foundation for high yield.(2) Influence on light distribution and light interception of potatoesMeasurement on layering and quantile of potatoes’PAR demonstrated that differences existed among PAR in terms of time and space and changed in a "W-shaped" manner along with the change of measuring sites, which showcased a synchronization relation between the interception of PAR and vertical structure of potatoes, with upper and middle parts of canopy intercepting the most. With the evolvement of breeding period, PAR interception during starch accumulation period was lower than that during tuber formative period.Besides, the perception of PAR was also affected by lighting direction. Following the lighting direction, light interception of middle and upper parts of potatoes away from maize line was higher than that of middle and upper parts of potatoes near the maize line. With a fixed radial width of potatoes (with a fixed small row spacing of maize), more PAR could be intercepted at each site when potatoes were arranged in wider spacing; the wider the spacing was, the more light energy obtained by the upper parts of leaves was and the augment of the row spacing could increase lower leaves’ capacity of light intercepting. The lower leaves could obtain more light when radial width of potatoes increased (small row spacing was fixed while spacing increased).(3) Influence on photosynthetic indexes of potatoesRelay-cropping lowered Pn, GS and Tr of potatoes and the lower the leaf position was, the lower the Pn, GS and Tr were.And increased Ci,the lower the leaf position was,the higher the Ci. In this experiment, Pn of relay-cropping was lower than that of sole cropping during the starch accumulation period for common effect of non-stomatal factors. Pn in treat1and7were relatively higher. Pn of middle and lower position were higher in treat1while Pn of upper position was higher in treat7, which was an energy basis for treat7to yield more than treat1.Correlation analysis on photosynthetic characteristics indexes of upper, middle and lower leaf position indicated the positive correlation between PAR and photosynthetic physiological indexes and between photosynthetic physiological indexes except Ci, yet different leaf positions displayed different significance. It is negative correlation between Ci and other photosynthetic physiological indexes.Intercropping accelerated the correlation between PAR and Pn, between indexes of middle-positioned leaves and indexes of lower-positioned leaves and between indexes of lower-positioned leaves.(4) Influence on active oxygen metabolism and membrane lipid overoxidation of potatoesIntercropping improved the augment of activity of SOD and CAT in potatoes and the content of MDA, but differences exited in different Conditions. The protective enzyme activity and membrane lipid peroxidation were closely related with light. The activity of SOD and CAT and content of MDA in treat7were the lowest, with scarce change within two hours.(5) Influence on dry plant tissue accumulation and yieldSmall row spacing of potatoes was the main constraint factor affecting the dry plant tissue accumulation of their stem and leaves in early stage of breeding period, while in middle and later stages spacing became the main constraint factor. Treat7enjoyed the most dry plant tissue accumulation of tuber. Relay-cropping decreased the yield of both potatoes and maize, in which potatoes’ yield witnessed more decrease. LER of all Conditions in this experiment were above1, which offered competitive advantage for intercropping.Composite production of treat7and4were the most,875.10kg/667m2and865.96kg/667m2respectively. No significant differences were between the two Conditions.