Regulation Of Root In Deep Soil Layers On Plant Growth And Yield Formation After Anthesis In Summer Maize

This study was conducted to evaluate the regulating effects of roots in different soil layerson plant growth after anthesis and yield formation in summer maize，aimed to providetheoretical supports for building high efficient root systems of maize and then increase grainyield of maize.Two high yield summer maize varieties, Zhengdan958(ZD) and Denghai661(DH), were used as experimental materials, and they were planted in soil columns. Threetreatments (without cutting the roots, CK; cutting maize roots at40cm below the surface atanthesis, T-40; cutting roots at80cm below the surface at anthesis) were designed to evaluatethe regulating effects of summer maize roots in different soil layers to shoot growth and yieldformation. The main results were as follows:1. Effect of deep roots on yield and yield components of maize in different treatmentsThe TTC reducing capacity was higher and duration of root activities was longer of rootsin deep layers than upper roots (0-40cm). Cutting upper roots (0-40cm) reduced maizeyield significantly. Intermediate roots (40-80cm) had significant influences on grainnumbers per ear and grain weight; deeper roots (below40cm) had significant effect on grainweight than grain numbers per ear. In high-yielding cultivation, keeping deep root activelycan increase the grain yield per unit area. This was significant to increase maize yield.2. Regulating effects on accumulation and translocation of nitrogen to deep rootsTotal root activity, nitrogen meTableolism enzymes (nitrate reductase, glutamatedehydrogenase and glutamate synthase) activity and nitrogen absorption capacity weresignificantly reduced due to cutting deeper roots. The nitrogen contribution rate to gains was leaves, followed by stems, sheaths and bracts. The regulation of upper roots to nitrogenuptake and translocation was the most significant. Loss function of deep roots (below40cm)reduced nitrogen absorption capacity, and then accelerated the transportation from nutritoriumto grain sink.3. Regulating effects on leaf physiological characteristics of nitrogen to deep rootsCutting deeper roots at anthesis significantly decreased green leaf area per plant,chlorophyll content, activity of SOD and Pn, and increased the content of MDA, shortened theduration of high photosynthesis and reduced biomass of plant and grain yield significantly.Reducing photosynthetic key enzyme activities inhibited the photochemical reaction proceeds,decreased the electron transfer rate, PS II actual photochemical efficiency and PS II maximumphotosynthetic efficiency, eventually leaded to the decline in leaf photosynthetic capacity.Maintain a deep root activity can delay leaf senescence and improve the net photosyntheticrate, to extend the duration of high photosynthesis.4. Effect of deep roots on bleeding intensity and bleeding components of root in differenttreatmentsCutting deep root reduced significantly bleeding intensity, root activity and contents ofMg, B, Fe and Zn in bleeding components of root. Deep roots in maize roots play animportant role in the absorption of trace elements.