Effects Of Different Plant-type Maize On Photosynthetic Physiological Characteristics And Yield Of Relay-cropping Sweetpotato

In this study, we choose 3 maize varieties with different plant-types (compact, semi-compact and expanded) and 3 starch-type sweetpotato varieties (yushu 2, yushu 6 and nanshu 88) to research the effect on the photosynthetic and physiological characteristics in intercropping of sweetpotato by different plant-types, by two-factors randomized block design,and eventually provide references for the cultural techniques for high-yield and better-quality and the response mechanism of photosynthetic in the intercropping of sweetpotato. The main results of this study are as follows:1. Effect on the overground growth in intercropping of sweetpotato by maize plant-types.The vine length of sweetpotato first decreased and then increased along with the extending of maize plant-type:it was longer in the monoculture than in the intercropping within 50d after planting while shorter after 50d after planting. However, the stem diameter, branch number and LAI of sweetpotato decreased along with the extending of maize plant-type:the vine length and the stem diameter of yushu 2 were the longest while the branch number and the LAI of nanshu 88 were the highest.2. Effect on the dry matter accumulation in intercropping of sweetpotato by maize plant-types.Both the dry matter weight of overground part and the starch-rate of sweetpotato decreased along with the extending of maize plant-type. The dry matter weight of storage root was very significantly higher in the monoculture than that in the intercropping at 70d after planting in the intercopping; the starch-rate of sweetpotato was slightly higher in the monoculture than that in the intercropping, however it was very significantly higher of yushu 6 than that of yushu 2and nanshu 88, and there were no significantly differences across different maize plant-types.3. Effect on the photosynthetic characteristics parameters in intercropping of sweetpotato by maize plant-types.The Ch1 a+ Ch1 b increased along with the extending of maize plant-type in intercropping, it was higher in intercropping than in monoculture, and slightly higher in expanded-type maize than compact and semi-compact maize, and the Ch1 a of B2 was the highest.The Pn, Gs, Ci and Tr decreased along with the extending of maize plant-type. They were all significantly higher in monoculture than in intercropping, except for Ci. The Pn of A1B2 and the Gs, Ci and Tr of A1B1 were the highest while the Pn, Gs, Ci and Tr of A3B3 were the lowest.The PAR of the top of sweetpotato was only 12.4%-20.3% on the top of maize because of the overshadow by maize, and the PAR across sweetpatatoes was the lowest. The plant-type of maize didn’t affect the PAR between the top of maize and sweetpotato. However, the PAR of the bottom of maize and the top of the sweetpotato, and between maize and sweetpotato decreased along with the extending of maize plant-type.The Fo and Y (Ⅱ) of sweetpotato increased while the Fv/Fm, qP and NPQ decreased along with the extending of maize plant-type. The Fo, Y (Ⅱ), Fv/Fm, qP and NPQ of A2B3, A3B3, A1B3, A2B3 and A1B3 were the highest, respectively, while these of A1B2, A1B3, A3B3, A3B1 and A3B3 were the lowest.4. Effect on the physiological metabolism in intercropping of sweetpotato by maize plant-types.The activety of RuBPCase of sweetpotato decreased while the activety of SPS increased along with the extending of maize plant-type at 50d after planting. Both the activeties of RuBPCase and SPS in intercropping were significantly higher than that in monoculture. The activety of RuBPcase of sweetpotato in compact was significantly higher than that in semi-compact and expanded while the activety of SPS in expanded was significantly higher than in compact and semi-compact. There were very significantly differences of the activeties of SPS across different varities, and the activety of SPS of B3 was the highest.The activeties of POD, CAT and SOD of sweetpotato in intercropping were higher in monoculture, and increased along with the extending of maize plant-type. The activeties of POD of A1B1 and CKB3, CAT and SOD of CKB1 were the lowest; the activeties of POD of sweetpotato in semi-compact and expanded increased at the level of 29.3% and 15.6%, respectively, compared with that in compact. The activety of POD of B2 was significantly higher than B1 and B3 varied different sweetpotato varities, and the activeties of POD, SAT and SOD of yushu 6 were significantly higher than others.The contents of Pro and MDA of sweetpotato in monoculture were higher in intercropping, and decreased along with the extending of maize plant-type. The contents of Pro and MDA of A2B3 were the lowest; these of sweetpotato in compact were significantly higher than in semi-compact and expanded; these of nanshu 88 were significantly higher than others.5. Effect on the yield by maize plant-types.The fresh yield of sweetpotato was significantly higher in the monoculture than that in the intercropping (70%,116% and 173% higher than A1, A2 and A3, respectively), and the grain yield of maize was B2>B3>B 1>CK with no significantlt differences across different maize varieties. The fresh yield of sweetpotato decreased along with the extending of maize plant-type with a significantly higher of compact than expanded and semi-compact, however, there were no sinificantly differences of the grain yields of maize across different sweetpotato varieties, but the yield of maize was A1>A3>A2 with a with a significantly higher of A1 than A2. The composite yield decreased along with the extending of maize plant-type with a significantly higher of A1 and A2 than A3. The fresh yield of sweetpotato across different sweetpotato varieties was B3>B2>B1 with a significantly higher of B3 than B2 and B1. The fresh tuber weight per plant and commercial sweetpotato number per plot of monoculture were significantly higher than that of intercropping. The total LER was 1.35-1.82 with an average of 1.58. All the intercropping treatments had great advantages in the yield with the highest in A2B1.6. Correlation analysis between the fresh yield and Pn of sweetpotato and other indexes.The fresh yield was very significant positive correlation with the content of MDA, very significant negative correlation with the activeties of POD, CAT and SOD, and significant positive correlation with the content of Pro and the activety of RuBP; Pn was very significant positive correlation with the content of MDA and Pro, very significant negative correlation with the activeties of protective enzyme, and significant negative correlation with the activeties of SPS.