Induction Of Root-shoot Signals And Regulation Of Yield Formation By Root Partition Irrigation In Spring Wheat

Since Blackman and Davies firstly proposed the theory of root-to-shoot communication in the root-splitting experiment in maize in 1985, a large number of experiments have certified the phenomenon of non-hydraulic root-sourced signal in plant and its regulatory effects on water saving and yield improving in crops. However, the theory is only based on pot experiment conditions of observation; there is a lot of the lack of empirical research under the condition of field production. Alternate irrigation (alternate partial root-zone irrigation, APRI) technology has been developed and showed great productive potential in the past few decades, but its physiological and ecological mechanism is not clear, we speculated that the mechanism is closely related with plant root-shoot communication process. To verify the theories, this paper test carried out the experiment of potted plant root partition water and the root partition irrigation experiment in field production. The experiment was conducted from 2013 to 2014 in greenhouse of Yuzhong experiment station, Lanzhou University. Use modern spring wheat varieties (Longchun 8275) by four different irrigation treatments (deficit irrigation DI; fixed furrow irrigation FFI; alternate furrow irrigation insulation AFI; sufficient water treatment CK) for two years field experiment and a year in pot. We analyzed the soil moisture change, physiological and ecological index, adjustment of root-sourced signals, plant growth, biomass allocation, yield formation and water use efficiency in the process of spring wheat growth. In order to illustrate the regulating effect of non-hydraulic root-sourced signals in APRI and the formation mechanism of spring wheat yield under APRI technology, in order to provide theoretical potential of agricultural APRI technology application to arid and semi-arid regions. Major results were achieved as follows:1. In pot experiment under water stress, the stomatal conductance of DI, FFI and AFI was significantly higher than that of CK (DI is 0.125 molCO2/m2s, FFI is 0.161 molCO2/m2s, AFI is 0.156 molCO2/m2s, CK is 0.183 molCO2/m2s), at the same time significantly improved the leaf ABA content (DI is 118.920 ng/g, FFI is 73.942 ng/g, AFI is 78.512 ng/g, CK is 52.313 ng/g). Although leaf relative water content and leaf water potential of DI was significantly lower than that of CK (DI were 76.287% and 2.969 Mpa, CK were 85.124% and 2.532 Mpa), the FFI and AFI processing leaf relative water content and leaf water potential only slightly lower than CK treatment with no significant difference (FFI were 82.745% and 2.752 Mpa, AFI were 83.348% and 2.638 Mpa). The result showed that the root partition watered treatments FFI and AFI induced the hydraulic source signal and its persistent effect.2. AFI treatment rationally adjusted the opening of stomata and significantly improved photosynthetic water use efficiency (WUE) (increased by 20.55% and 24.79% respectively) despite photosynthesis slightly is less decreased (decrease by 4.85% and 4.15% respectively compared with CK).3. In partial root-zone irrigation treatments AFI and FFI, the yield is increased significantly compared with DI (34.68% and 33.75% respectively). Their biomass water use efficiency (WUEB), compared with DI and CK treatment, increased by 10.03% and 10.03%,6.76% and 14.97%, respectively. The yield water use efficiency (WUEY) compared with DI and CK, increased by 21.32%and 24.45%,19.52% and 22.60% respectively.4. Two years field experiment results showed that both flowering and filling stage, with the increase of days in irrigation cycle, the stomata conductance of AFI and FFI were significantly lower than that of CK on the basis of slow fall in leaf water potential and leaf relative water content. At the same time, the ABA contents of leaves and stems had significant upward trend. The ABA content of wheat leaves and stems enhanced from 50 ng/g to 150 ng/g and 10.2ng/g to 21.2ng/g in 2013 and 2014 flowering stage. Further, wheat leaves and stems ABA content also enhanced from150 ng/g to 195ng/g and 12.5ng/g to 28.5ng/g in filling stage in 2013 and 2014. Therefore, it has verified the function of root-shoot source signal regulation in spring wheat production under the condition of FFI and AFI.5. At the same time, compared with high water treatment CK in 2013 and 2014, the transpiration rate, photosynthetic rate and intercellular CO2 concentration of AFI treatment reduced by 36.87%,11.28% and 36.87% respectively; 21.46%,9.68% and 32.56%, and the instantaneous water use efficiency increased by 22.71% and 17.15%, respectively. This shows the great biological water saving ability of AFI.6. In field experiment conditions in 2013 and 2014, the yield production in AFI treatment was 21.02% lower than CK, but compared with DI treatment increased by 23.56%; at the same time its WUEB and WUEY increase by 68.00%,17.72% and 56.40%,68.00% respectively compared with DI and CK treatment in 2013. AFI treatment in production was 23.41% lower than CK, but compared with DI treatment increased by 34.84%; meanwhile, WUEB and WUEY increase by 44.05%,43.88% and 40.47%,44.05% respectively than DI and CK treatment.7. Pot experiment and field experiment results showed that AFI treatment enhanced the effective tiller number by spring wheat (increased by 16.95% in 2013; increased 29.70% in 2014; and increased 26.2% in pot experiment) and effective photosynthetic leaf area (enhanced 32.25% in 2013, while 29.98% in 2014; and 34.0% in pot experiment). At the same time, compared to CK, AFI significantly increased the antioxidant enzymes activity (SOD increased by 5.21%; CAT increased by 92.11%; the POD increased by 40.85%), by reducing the damage in spring wheat under drought stress so improving the drought adaptability of spring wheat.By concluding all this study, on the basis of production of root-shoot signals and its persistent effect, the partial root-zone irrigation treatment AFI can optimizes the stomatal conductance and adjusts the leaf water status and in the stability of leaf photosynthetic rate significantly improves the leaf water use efficiency. So by, improving the ability of spring wheat population due to increasing photosynthetic rate enhanced the effective tiller number by spring wheat and effective optical hinges. As a result, the biomass and yield of wheat have a huge improvement. So by conclusion we can say that, APRI technology has remarkable water-saving effect to increase production. In plant, generally the physiological and ecological mechanism is closely associated with the process of plant root-shoot communication, and our research results showed that our speculation, both for APRI technology provides theory basis for further optimization and integration, while at the same time broaden the root-shoot communication theory application potential in agricultural production practice.