马铃薯/玉米不同行比套作对马铃薯生理特性和群体产量的影响

以马铃薯中薯5号(早熟,株型直立)和米拉(中晚熟,株型扩散)单作为对照,设置2∶2和3∶2两种套作行比,研究大田条件下马铃薯/玉米套作模式中2个品种块茎形成期至块茎增长期群体光合有效辐射(PAR)和生理特性的差异及其对群体产量的影响。结果表明,从块茎形成期至块茎增长期,两品种PAR、可溶性蛋白含量(SPC)均呈下降趋势,中薯5号脯氨酸含量(Pro)、丙二醛含量(MDA)、过氧化氢酶(CAT)活性呈上升趋势,超氧化物歧化酶(SOD)活性呈下降趋势,过氧化物酶(POD)活性的变化因行比而不同;米拉MDA、CAT呈下降趋势,SOD相近,Pro、POD的变化因行比而不同。套作降低了两品种SPC,提高了两品种Pro、SOD、POD。中薯5号PAR套作低于单作,MDA套作高于单作,CAT块茎形成期低于单作,块茎增长期高于单作;米拉PAR套作高于单作,MDA、CAT套作低于单作。两品种套作PAR和CAT 3∶2行比高于2∶2行比,SPC相近,其他生理指标因生育时期而不同。套作降低了中薯5号的光环境,提高了米拉的光环境,3∶2行比光环境优于2∶2行比。套作条件下米拉的耐荫性比中薯5号更强,两品种3∶2行比套作比2∶2行比套作耐荫性更强。光环境的变化导致生理特性的变化,并使套作马铃薯块茎产量显著降低。中薯5号和米拉2∶2行比套作LER分别为0.88,1.00,均无套作优势;3∶2行比套作LER分别为1.24,1.40,具有较强的套作优势,后者宜在生产中推广。

Effects of a potato/maize intercropping system on physiological characteristics and total yield with two potato varieties at different row ratios

The intercropping of potato (Solanum tuberosum) and maize (Zea mays) is a traditional cropping pattern in southwest China. Potato/maize intercropping trials were carried out to determine the dynamic changes of photosynthetical active radiation (PAR), soluble protein content (SPC), proline content (Pro), malondialdehyde content (MDA), superoxide dismutase (SOD), peroxide dismutase (POD), and catalase activities (CAT) from the tuber initiation stage to the tuber expansion stage. The yield was also studied using monocropped potato as the control. Two potato varieties: Zhongshu 5 (early-maturing variety with erect branches) and Mira (mid-late maturing variety with spread branches)were employed as well as two potato to maize ratios. The ratio 2∶2 meant two rows of potato to two rows of maize and 3∶2 meant three rows of potato to two rows of maize. Gradual decreases in PAR and SPC were observed from the tuber initiation stage to tuber expansion stages in both Zhongshu 5 and Mira. However, there were gradual increases in Pro, MDA, CAT and a decrease in SOD in Zhongshu 5 but decreases in MDA, CAT and a similar SOD activity in Mira. POD activity in Zhongshu 5 and Pro and POD activity in Mira had different trends due to row ratios. In addition, intercropping led to lower SPC and higher Pro, SOD and POD in the two potato varieties. Lower PAR, higher MDA, and lower CAT at the tuber initiation stage and higher CAT at the tuber expansion stage in Zhongshu 5 were also detected, as was a higher PAR and lower MDA and CAT in Mira compared with the monocropped plants. Moreover, higher PAR and CAT in the 3∶2 intercropping system than in the 2∶2 intercropping system were observed, as well as a similar SPC. Other parameters changed differently due to growth stages. Nonetheless, intercropping reduced the light environment in the Zhongshu 5/maize system but improved it in the Mira/maize system. A better light environment was found in the 3∶2 than in the 2∶2 systems. Mira was more tolerant to shade than Zhongshu 5 while both Mira and Zhongshu 5 were more tolerant to shade in the 3∶2 combination than in the 2∶2 one. In summary, a varied light environment in intercropping led to substantial changes in physiological characteristics of potato and a reduction in tuber yield at harvest. LERs were 0.88 and 1.00 in the 2∶2 intercropping potato/maize system for Zhongshu 5 and Mira, respectively, while it was 1.24 and 1.40 in the 3∶2 system. It is suggested that there is no intercropping advantage in a 2∶2 potato/maize system but an obvious advantage in the 3∶2 system with better production in the latter.