The Response Of Water-use Efficiency To Drought, High Temperature, Fungal Inoculation And Other Environments

The research of this paper was conducted in drought, high temperature, fungal inoculation and other several different environments to evaluate water use efficiency, photosynthetic characters and other relative items. On the Loess Plateau, (1) 8 varieties were analyzed to see the differences between their water use efficiency, sap flow velocity and gas exchange parameters, (2) using 3 different P levels on another wheat variety Changwu 134 to see the water use efficiency and other characters changes. There were also some experiments conducted in Alberta, Canada, (1) In greenhouse condition, under high temperature and water-deficit treatments the relationship between water use efficiency and arabinoxylan fractions of spring wheat was analyzed; the fungal inoculation to nutrient uptake and water use efficiency change were also analyzed; (2) Under drought field conditions, the inoculation of different fungi and different P levels adding were used to measure the differences of the water use efficiency. Those researches of water use efficiency under these several environments and combined the yields and other characters, which is useful to the wheat variety selection and cultivating model. Main results are as follows:1. The results of photosynthetic characters showed that the value of leaf photosynthesis rate at stem elongation stage was higher than that at flowering stage, and the value of leaf transpiration rate at stem elongation stage was also higher than that at flowering stage. For the results of instantaneous WUE, it showed that under the wheat variety experiment the instantaneous WUE was higher at stem elongation stage than that at flowering stage; but in phosphorus experiment, the instantaneous WUE was a little higher at flowering stage, and the highest value of the WUEi at both stages was under F1 treatment, and it was 3.04 and 3.77 umol CO₂/mmol H₂O respectively. It showed that adding P could increase the instantaneous WUE. The SPAD of LuoYang 8716 at stem elongation stage was the highest and had significant differences among 8 varieties, and the yield of the LuoYang 8716 and Shaan Mai 893 were the highest. Both the SPAD and the yield of F2 was the highest among 3 different phosphorus treatments.2. The results of the sap flow showed that curves of daily sap flow velocity firstly rose up and then dropped down. In phosphorus experiment, the highest sap flow velocity in a day was 2.796,3.734and 3.873 g/h under F0, F1 and F2 respectively, and the sap flow was increased by the P adding. Radiation had a greater impact on sap flow change during many environment factors. The correlation analysis of time synchronization for sap flow velocity and leaf transpiration rate showed that there was a significant positive correlation between them but had the hysteretic nature of the time, and that maybe because the water capacitance had effect on the water movement.3. Under a controlled environment of water-deficit (imposed at the stem elongation stage) and high temperature (imposed at the booting stage), the water use efficiency (WUE) and arabinoxylan concentration of two spring wheat varieties ('Superb'and'AC Crystal') were analyzed. The temperature treatments were 22/12 (day/night) and 32/22℃. Overall, time to maturity under high temperature was 10 days shorter for'Superb'than for'AC Crystal', indicating that'Superb'was more sensitive to high temperature stress. Leaf relative water content (RWC) and specific leaf area (SLA) were more sensitive to drought than to high temperature for both varieties. Drought and high temperature decreased (P < 0.05) biomass, water use and grain yield but increased WUE of'Superb'and'AC Crystal'. Without temperature stress, significant drought and variety effects were found on CID (carbon isotope discrimination) which was negatively correlated with WUE. All gas exchange parameters declined under drought and high temperature. High temperature increased the grain arabinoxylan concentration (especially the water-extractable arabinoxylans). The different arabinoxylan fractions were positively correlated with WUE suggesting that arabinoxylans can be increased by selecting for increased WUE.4. Arbuscular mycorrhizal fungal inoculation, nitrogen adding (180 kg/hm2) and drought (imposed at the stem elongation stage, 40% filed capacity) were used to analyze changes of the water use efficiency, nitrogen and phosphorus uptake. The nitrogen adding and fungal inoculation can improve the leaf relative water content, but drought decreased it; drought decreased the specific leaf area, but nitrogen adding and fungal inoculation increased it. The water use efficiency was improved by drought, while under the same nitrogen level, fungal inoculation didn't have much impact on water use efficiency; nitrogen adding and drought all decreased the leaf carbon isotope discrimination. Under different treatments, the leaf and stem nitrogen concentrations were changed a lot and the phosphorus concentrations of different parts were also improved by drought and fungal inoculation, while nitrogen adding indirectly influenced the stem uptake of phosphorus but not seed.5. This experiment evaluated the combined effects of fungal (arbuscular mycorrhizal (AM) and Penicillium) inoculations and phosphorus (P) fertilization (0, 45 and 90 kg/ha) on the net rate of photosynthesis, water use efficiency, P uptake and the growth of spring wheat (Superb) under field conditions at two locations (Castor and Vegreville) in Alberta, Canada. The results showed that both fungal inoculation and P application increased the rate of photosynthesis. Under the same P level, AM inoculation had a greater positive effect on the rate of photosynthesis than Penicillium. The AM inoculation increased the instantaneous water use efficiency (WUEi) of plants at Castor but not at Vegreville. The carbon isotope discrimination (Δ¹³C) of the leaves increased with the rate of P application but was not affected by fungal inoculations. Phosphorus concentrations of stem and seed increased with both fungal inoculation and P application irrespective of location, with AM inoculation showing the largest effects. The interaction between P and fungi was significant for stem P concentration in plants grown in Vegreville. Both Fungal inoculations and P application increased the leaf area index (LAI), biomass and grain yields at both locations.