The Impact Of Elevating CO₂Concentration And Temperature On Winter Wheat Growth And Water Requirement

It is an indisputable fact that the greenhouse effect which caused by the increasing concentration of CO2, the effect of this change on growth and water demand of food crops is attracting all of attention. This study discussed the effect of elevated CO2concentration and temperature on the winter wheat growth and water requirement by using2012-2013OTC test, also observe the changes of elevating CO2concentration on wheat water requirement. This paper simulated and analysied the OTC test of CO2and temperature by using improved WOFOST model, explored the mechanism of climate change on growth and water requirement of winter wheat. For further improvement the model and formulate crop irrigation system to adjust high CO2concentration and high temperature weather conditions this study provides theoretical foundation. The main conclusions are as follows:(1) To achieve the localization model WOFOST by adjusting parameters of winter wheat in North China.By2010-2011winter wheat test data of two normal sowing date to adjust WOFOST model adaptation and determine the main parameters. Then simulated and validated winter wheat growth and development of2009-2010two normal sowing date and three other sowing date. The results show that the model can mainly reflect the winter wheat growth and estimate yield.(2) To analyze the effects of elevated CO2concentration and temperature on physiological ecology and yield of winter wheat in field trials.①By2012-2013winter wheat OTC test observing and analyzing the change of physiological and ecological indicators under elevated CO2concentration and temperature. The results show that increased CO2concentration and temperature can shorten the growing period of wheat, enhance leaf area index (LAI) and green leaf dry weight, and the temperature effect was more obvious. Elevated CO2concentration and temperature can be enhance stem weight, but high CO2concentration increased stem weight and height in proportion, so that the stem was more robust. While high temperature increased the height faster than stem weight, so the plant was prone to lodging. On the flag leaf analysis found that elevated CO2concentration and temperature will increase the flag leaf area, and the CO2effect was more obvious. Elevated CO2concentration will increase leaf thickness and chlorophyll content, elevated temperature on the contrary. However both can cause the leaf water content increases. High temperature will improve stomatal conductance and increase transpiration, while high CO2concentration will reduce stomatal conductance, thereby reducing transpiration of per unit leaf area. Use the pots weighing to measure winter wheat water requirement from jointing stage to milky stage found with increased CO2, water requirement will increase.②Elevated CO2concentration and temperature will increase spike length, thereby increasing the number of spikelets. But high temperature will increase the infertile spikelets, resulting in decreasing grain number and grain weight, high CO2concentration on the contrary. Elevated CO2concentration and temperature will improve the total spikes. High CO2concentration can lower ineffective spikes further improving yield. Although grain weight decreased, due to total spikes augment, increased double CO2concentration can mainly offset the negative impact on yield of increasing4℃temperature.(3) To improve simulation method of CO2concentration affected winter wheat growth and development, and try to simulate the influence of elevating CO2concentration on water requirement.According to previous experience to improve the WOFOST model in photosynthetic rate and stomatal resistance to the CO2factor sensitivity did indicate that the improved model can reflect the increase CO2concentration in winter wheat growth scenario. According to the observed experimental data fitting equation for improving model in dry matter partitioning coefficient to simulate winter wheat growth and water requirement of elevating CO2concentration and temperature with the localized model. The results show that improved WOFOST model can more accurately reflect the effect of high CO2concentration and temperature on winter wheat main physiological processes and yield. The model evapotranspiration simulation revealed the simulated and measured values of goodness is good, but the model mechanisms and experimental error lead to the biggest difference from jointing stage to booting stage. The total evapotranspiration simulated and measured values of the absolute error were less than30mm. However, the model of water requirement simulation is needed to improve, and the error from water requirement of trial observation to water requirement of theoretical formulas need a more comprehensive testing to eliminate, as well as more test data to verify.(4) To preliminary analyze the effect mechanism of elevating CO2concentration on winter wheat water requirement.The effect of CO2concentration on water requirement is mainly affecting transpiration. Elevated CO2concentration will enhance leaf area and improve light saturation point. Leaf is the important place of photosynthesis. In the fact, transpiration is more sensitive for leaf area and light. Larger leaves and more photosynthetically active radiation accelerated physiological and biochemical reaction of winter wheat, they will accumulate more dry matter. Forever, increasing the biomass of wheat will increase the body’s water cycle, so increasing transpiration. This point proved by the experimental observation of leaf water content rising. The study also found that high CO2concentration will promote the sensitivity of temperature for water requirement, resulting in more increasing on water requirement from flowering stage to milky stage.