Effects Of Water And Phosphorus On Yield Formation In Different Ploidy Spring Wheat

In order to understand the effects of water and phosphorus on root function efficiency and yield, a potted plant experiment was conducted to investigate three different ploidy (diploid, tetraploid and hexaploid) spring wheat for growth, water use efficiency, root-shoot ratio and grain yield so that the differences between various ploidy as affected by water and phosphorus regimes on these traits can be found out. Two soil water treatments were employed: drought stress (D, 40～50% of field water capacity) and well-water supply (W, 70～80% of field water capacity). Two phosphorus treatments were also employed: no phosphorus and suitable phosphorus. In joiting and flowering stage, shoot biomass, root biomass, height and leaf area were measured. Grain yield and everyday water consumption were also measured. The main results were listed as follows:1. In the evolution of wheat from diploid to tetraploid and hexaploid, height and leaf area increased correspondingly under either drought stress or well-watered conditions. In different treatments, the difference was not the same between ploidy levels. Phosphorus and water played important roles in whole growth stage. Overall, the effects of the interaction between water and phosphorus to leaf area on different ploidy were significant. As to height, the synergism of phosphorus under drought stress condition to hexaploid was the largest (In jointing stage was 33.1%, and in flowering stage was 30.33%). To area leaf, the effect was largest under well-water supply while employed with phosphorus (In jointing stage was 230.02%, and in flowering stage was 235.99%).2. Under two water treatments, root and shoot biomass all increased with the evolution of wheat, but the root-shoot ratio decreased adversely. Phosphorus deficit significantly reduced the dry matter which played the most important role in hexaploid. Water and phosphorus deficit can raise the root-shoot ratio but the effects on different ploidy were not significant.3. With the evolution from diploid to hexaploid, water consumption firstly raised and then descended which may be correlated to the growth period. And water use efficiency for biomass and grain yield both increased by the evolution of wheat. The effects of interaction between water and phosphorus were extremely significant on water consumption and water use efficiency for biomass of diploid, but there was no significant influence for tetraploid and hexaploid. In addition, the interaction had no much effect on different ploidy of water use efficiency for grain yield.4. Water use efficiency and grain yield were affected significantly by phosphorus. The synergism of phosphorus under drought stress condition to hexaploid was the largest (grain yield improved 158.33% ). Grain yield improved which was directly related to the remarkable increase of harvest index and the decrease of root-shoot ratio. However, the root function efficiency of latterly varieties was higher than the wild because they reduced the consumption of nutrition in root which can be moved more to the vegetative organs.