Studies On Water Requirement Characteristic For High Quality And Grain Yield And Its Physiological Basis In Wheat

1 Effect of irrigation rate on quality and grain yield and its physiological basis in wheatEffect of irrigation rate on the water requirement characteristic, the physiological metabolism of carbon and nitrogen mechanism, the formation of grain yield and quality in wheat was studied by using two wheat cultivars including Jimai20 which with strong gluten potential and Taishan 23 which with medium gluten potential. Set up three treatments including no irrigation (expressed as W0), irrigation at jointing stage and anthesis stage (expressed as W1), irrigation at jointing stage, anthesis stage and filling stage (expressed as W2), the irrigation rate was 60mm once. The principal results were as follows.1.1 Effect of irrigation rate on soil moisture contentAccording to the distribution and development principle of wheat roots, soil layers of 0¹40cm were divided into 4 layers: 0²0cm, 20⁶0cm, 60 100cm and 100¹40cm. The soil moisture content of 0²0cm, 20⁶0cm, 60¹00cm and 100¹40cm soil layers were 17.73%, 17.02%, 16.90%, 17.60% before sowing, the soil moisture content of the above-mentioned soil layers of high grain yield treatment in this experiment were 8.80%⁹.20%, 12.10% 13.13%, 16.10%¹6.19%, 17.89%¹8.35% at jointing stage; 7.03%⁹.24%, 12.25%¹3.89%, 15.53%¹6.14%, 16.23%¹7.40% at anthesis stage; 4.86% 7.40%, 9.08%⁹.95%, 12.61%¹4.55%, 15.95%¹6.24% at maturity; respectively. To ensure high grain yield, 20⁶0mm soil layers from jointing stage to anthesis stage and 60¹00mm soil layers from anthesis stage to filling stage must be contained proper water content.1.2 Effect of irrigation rate on water consumption rate of wheatThe contribution percentage of precipitation to total water consumption rate ranged from 43.82% to 46.41%, the contribution percentage of irrigation rate to total water consumption rate ranged from 26.82% to 28.40%, the contribution percentage of soil water consumption rate to total water consumption rate ranged from 25.19% to 29.36%. The increasing of irrigation rate at the base of treatment W1 increased the contribution percentage of irrigation rate and decreased the contribution percentage of soil water consumption rate to total water consumption rate while there was no significant effect on grain yield. At the stage from anthesis to maturity, the stage water consumption percentage ranged from 46.73% to 46.97%,the daily water consumption rate ranged from 5.67 to 5.97mm·day^-1, they were higher than these of other stages. With the increasing of irrigation rate, the stage water consumption percentage and the daily water consumption rate increased.The total water consumption rate of Jimai20 which had the grain yield from 7745.57kg·hm-2 to 9231.45kg·hm-2 ranged from 364.21mm to 422.55mm .The total water consumption rate of Taishan23 which had the grain yield from 7719.18 kg·hm-2 to 9663.65kg·hm-2 ranged from 386.03mm to 447.49mm. The total water consumption rate increased with the increasing of irrigation rate.1.3 Effect of irrigation rate on soil nitrate leachingThe soil nitrate of treatment W1 and W2 had leached in 80cm soil layer at anthesis stage. The soil nitrate of treatment W1 was detained in 40⁸0cm soil layers mainly at maturity and treatment W3 made the soil nitrate leach in 140cm soil layer. The soil nitrate of the treatment W0 was detained in 0²0m soil layer mainly with little leaching during the whole growth stage.1.4 Effect of irrigation rate on nitrogen metabolism in flag leaf and quality in wheatWith the increasing of irrigation rate, the Glutamine synthetase (GS) activity, the endopeptidases (EP) activity from 21DAA to 35DAA, the soluble acid amino content and the free amino acids content in flag leaf increased until the irrigation rate of treatment W1. In treatment W2, the soluble acid amino content and the free amino acids content in flag leaf from 21DAA to 35DAA was increased.The protein content, glutenin and its components content, gliadin and its components content, was increased in treatment W1; the dough stability time was increased too. The protein content, HMW-GS content, glutenin content and the dough stability time of treatment W2 was declined. The gliadin content of treatment W2 was increased.Jimai20 had longer dough stability time than Taishan23.1.5 Effect of irrigation rate on carbon metabolism and grain yield in wheatThe activity of soluble starch synthase (SSS) and granule bounded starch synthase (GBSS) in kernels from 21DAA to 35DAA was increased in treatment W1; the GBSS activity in kernels and DP=3 fructan content in penult stem and sheath at 28 DAA was increased, the SSS activity in kernels from 21DAA to 35DAA was declined in treatment W2.The amylopectin content, amylase content, total starch content and grain yield was increased at maturity in treatment W1. The amylopectin content, total starch content was declined at maturity in treatment W2, but there was no significant difference between treatment W1 and W2 on grain yield.The grain yield of Taishan23 was higher than that of Jimai20 under irrigation conditions.2 Regulation of irrigation rate and nitrogen fertilizer rate on formation of quality and grain yield in wheatThe regulation of irrigation rate and nitrogen fertilizer rate on the water requirement characteristic, the physiological metabolism of carbon and nitrogen mechanism, the formation of grain yield and quality in wheat was studied by using wheat cultivar Jimai20 which with strong gluten potential. Set up four treatments of different irrigation rates: no irrigation(expressed as W0); irrigation at jointing stage and anthesis stage, the irrigation rate was 30mm (expressed as W1), 60mm (expressed as W2), 90mm (expressed as W3) once and four treatments of different nitrogen fertilizer rates: no nitrogen (expressed as N0), 120kg·hm-2 (expressed as N1), 210 kg·hm-2 (expressed as N2), 300 kg·hm-2 (expressed as N3).2.1 Effect of irrigation rate and nitrogen fertilizer rate on water utilizationThe treatment N2W2 which had higher grain yield water use efficiency, protein yield water use efficiency and lower consumption coefficient than other treatments is better to achieve the aim of high grain yield with high efficiency.In treatment W2N2, the contribution percentage of precipitation to total water consumption rate ranged from 32.28% to 32.58%, the contribution percentage of irrigation rate to total water consumption rate ranged from 30.26% to 30.54, the contribution percentage of soil moisture rate to total water consumption rate ranged from 36.88% to 37.47%, it was propitious to utilize different sources of water equally. The increasing of irrigation rate at the base of treatment W2 improved the contribution percentage of irrigation rate and decreased the contribution percentage of soil moisture rate to total water consumption rate while had no significant effect on grain yield.The stage water consumption percentage from anthesis stage to maturity ranged from 47.59% to 48.74%,the daily water consumption rate ranged from 4.60 to 5.01mm·day^-1. With the increasing of irrigation rate, the stage water consumption percentage and the daily water consumption rate increased.The total water consumption rate of Jimai20 which had the grain yield from 6752.18 kg·hm-2 to 8040.45kg·hm-2 ranged from 364.21mm to 449.64mm. The total water consumption rate of Taishan23 which had the grain yield from 7719.18kg·hm-2 to 9698.78kg·hm-2 ranged from 348.31mm to 396.59mm. The total water consumption rate increased with the increasing of irrigation rate.2.2 Effect of irrigation rate and nitrogen fertilizer rate on nitrogen cycle in plant and soil system of wheatThe nitrogen uptake rate of kernels and vegetative organs increased in treatment W2 at maturity. The increasing of irrigation rate at the base of treatment W2 improved the nitrogen uptake rate of vegetative organs but decreased that of kernels.In treatment N2,the nitrogen uptake rate of kernels and plants increased at maturity. The increasing of irrigation rate at the base of treatment W2 increased the nitrogen uptake rate of vegetative organs while there was no significant effect on the nitrogen uptake rate of kernels.The increasing of irrigation rate improved the soil nitrate leach to deep soil layer. Under the conditions of treatment N0, N1 and N2, the treatment W2 had no significant accumulation of soil nitrate. The treatment W2 and W3 had significant accumulation in soil layers from 140cm to 160cm. With the increasing of nitrogen rate, the content of soil nitrate increased in soil layers from 80cm to 100cm. The combination that irrigated at jointing stage and anthesis stage with 60mm irrigation rate and 210kg·hm-2 nitrogen rate was the reasonable style under this experiment conditions.2.3 Effect of irrigation rate and nitrogen fertilizer rate on nitrogen metabolism in flag leaf and quality in wheatThe protein content, HMW-GS content, glutenin content, gliadin and its components content and dough stability time was increased in treatment W2. The protein content, glutenin and its components content and dough stability time was declined while gliadin and its components content was increased in treatment W3.The protein content, glutenin and its components content, gliadin and its components content and dough stability time was increased in treatment N2. The glutenin and its components content, gliadin and its components content and dough stability time was declined in treatment N3 while there was no significant difference on protein content between treatment N2 and N3.In treatment W2, the GS activity from 7DAA to 28DAA, the EP activity from 14DAA to28 DAA, the soluble acid amino content from anthesis to 21DAA and the free amino acids content after 7DAA was increased in flag leaf. In treatment W3, the GS activity from anthesis to 28DAA, the EP activity from 14DAA to28 DAA was declined in flag leaf; the free amino acids content from 7DAA to 28DAA was declined, and the soluble acid amino content at 28DAA was increased in flag leaf.With the increasing of nitrogen rate, the GS activity and the EP activity,the soluble acid amino content and the free amino acids content in flag leaf was increased until the nitrogen rate of treatment N2.2.4 Effect of irrigation rate and nitrogen fertilizer rate on carbon metabolism and grain yield in wheatThe photosynthetic rate after anthesis, the granule bounded starch GBSS activity from 14DAA to 28DAA in kernels, the SPS activity and sucrose content from 14DAA to 28DAA in flag leaf was increased in treatment W2, but there was no significant difference between treatment W2 and W3 on SPS activity and sucrose content in flag leaf. The amylopectin content, total starch content was declined while amylase content and grain yield was increased at maturity in treatment W2. The DP≥4, DP=3 fructan content in penult stem and sheath from 28 DAA to 35DAA in treatment W3 was increased. The amylopectin content of treatment W3 was declined while there was no significant difference on amylase content, total starch content and grain yield between treatment W2 and W3.With the increasing of nitrogen rate, the SPS activity and sucrose content after anthesis in flag leaf was increased until the nitrogen rate of treatment N2. The grain yield of treatment N2 was increased but the amylase content; total starch content was declined while there was no significant difference on amylopectin content between treatment N1 and N2 at maturity. In treatment N3, the DP≥4 fructan content in penult stem and sheath from 21DAA to 35DAA was increased and the DP=3 fructan content in penult stem and sheath at 28DAA was increased; amylopectin content, total starch content was declined at maturity while there was no significant difference on amylase content and grain yield between treatment N2 and N3.