Mechanism Of Quality Formation And Key Cultural Technique Of High-protein Maize Cultivars

The quality character of maize grains is quantitative character controlled by multi-genes,whose expression is affected by environmental factors.The researches have been well-reported,but the mechanism of environmental factors and cultivation measures regulating protein content remain largely unknown.Although normal maize cultivars are well trailed,few high-protein maize cultivars are used as material.Moreover the effect of natural factors and cultivation measure on protein components is not comprehensively investigated.In the paper,it was studied that the physiological and biochemistry mechanism by which the high protein formed in maize seeds to find the best cultivation measure and the ecology region where maize grew best by using the materials of high-protein maize Yudan2002 and normal maize Zhengdan 136 in Henan Province.The main results are as follows:1.Character of nitrogen metabolism in high-protein maize seedsNitrogen use efficiency of high protein maize(Yudan2002)was 7.79%higher than that of normal maize(Zhengdan 136);The change trend of NRase in above two cultivars was similar. NRase activity in Yudan2002 was higher than that in Zhengdan 136 in those days from the 30^thday after pollination to the 45^thday after pollination except the days before the 30^thday after pollination.The change tendency of GS activity was the same as "∽" in both Yudan2002 and Zhengdan136 at the filling stage,but GS activity in Yudan2002 was higher than that in Zhengdan 136.High activity was benefit for generating protein.High protein in high-protein maize seeds belonges to its character with high use efficiency and high activities of nitrogen assimilation enzymes.2.Change in protein components and relevant enzyme activities in high-protein maize seedsDynamic change in protein and protein components content in both high-protein maize cultivars and normal maize cultivars assumed decreasing tendency.Protein content in former was higher than that in latter during development.Albumin content in high-protein maize seeds was higher than that in normal maize seeds during the whole development and globulin content in the former was also higher than that in the latter during 5-15 days after pollination, and it was opposite during 15-50 days after pollination.Albumin and globulin content in two maize seeds were not significantly different.Gliadin content in high-protein maize seeds was lower than that in normal maize seeds.The difference of glutenin between two genotype maize cultivars was small during 5-25 days after pollination and increased from 25 days after pollination.NRase and GS content in high-protein maize seeds were higher than that in normal maize seeds though their change trend was consistent.NRase activity was positive correlation to protein accumulation in single seed and GS activity change was consistent in protein accumulation speed in maize seeds.Time of GS peak was earlier than that of protein accumulation speed peak in both genotype maize cultivars.Amino acid content in seeds of high-protein maize cultivars was higher than that in normal maize cultivars,but it was lower in ear leaf of high-protein maize cultivars than that in normal maize cultivars and amino acid could not be transported quickly from ear leaf to seed so that protein in seeds formation became slowly.3.Change in endogenous hormone content in high-protein maize seed during developmentIAA content in two cultivars changed as parabola.Change in IAA quality liked split-blip curve and the general trend raise.Both IAA content and quality in Yudan2002 seeds were higher than that in Zhengdan136 during early and later grain filling period and they were opposite during intermediate grain filling period.Change in ZR content in high-protein maize seeds showed the single peak curve and the time arrived peak was the 15^thday.Change in ZR content in normal maize seed showed "M" curve and the first peak was much higher than the second.Change in ZR quality of both of two cultivars showed double peak curve and the time arrived the first peak was same but the time arrived second peak was different.GA₃ content in Yudan2002 seeds decreased slowly and GA₃ content in Zhengdan136 seeds increased quickly during 5-10 days after pollination and decreased quickly during 10-15 days after pollination,and then to keep steady.GA₃ content in Yudan2002 seed was higher than.that in Zhengdan136 during development.GA₃ quality in single seed of both cultivars increased and GA₃ content in single seed of Yudan2002 was lower than that in Zhengdan136 before the 32^th day after pollination and higher later.There was no difference on the 45^thday between two cultivars.ABA contents in Yudan2002 and Zhengdan136 seeds decreased during development and ABA content in the high-protein cultivars was lower than that in the normal cultivars. ABA quality in single seed of the both cultivars increased during development.ABA quality of Zhengdan136 was higher than that in Yudan2002 before the 37^thday after pollination.The high content of IAA and ZR during the initial period of seed growth and the low content of ABA and the GA3 at seed filling stage were benefit for protein synthesis.The relativity between NRase activity and GA₃ quality was obvious.The changes in protein content in seeds are regulated by various endogenous hormones and the interaction between these hormones could be the physiological foundation on which the protein content synthesizes.4.Studies on the daily variation of correlated physiological characters in high-protein maize cultivars.The dynamic change of protein content in Yudan2002 at the 30th day was similar to that of Zhengdan136.The protein content was highest at 20 o'clock and lowest at 2 o'clock.The dynamic change in the NRase activity in seeds and ear leaf was consistent with that of the protein content in seeds,and the NRase activities in seeds and ear leaf of high-protein maize cultivars during 30th day were higher than that in normal maize cultivars.The GS activities in seeds of Yudang2002 were higher than that of Zhengdan136 and the GS activity in the ear leaf was higher during 8-11 o'clock and lower during the other time.The proteinase activities in the seeds of normal maize cultivars were higher than that in the high-protein maize cultivars,and the verse in the ear leaf,which was benefit for transporting nitrogen from leaf to seed.5.Studies on ecological adaptability of high-protein maize cultivars.The protein content and the yield were different in different zones of Henan Province.The protein biosynthesis was affected by accumulated temperature,light time and humidity.The relativity between temperature and the protein content was the most obvious.Protein components were different in different zones and four kinds of components were affected by environment,but their change rules were different.Effect of the different years on the protein content was slighter than the different ecological zones.West watered area of Henan Province was suitable to high-protein maize cultivars grow.6.Effect of planting densities on the yield and quality of high-protein maize.The change trend of the yield was "increase-decrease" and that of the protein content was "increase-decrease-increase" following the densities increase.45 000 plant·hm^-2was the most suitable density for high-protein maize cultivars to grow.The content of protein components changed following different densities,and the gliadin was affected the most easily.7.Effect of soil texture on the yield and quality of high protein maize cultivars.The yield and the protein content of high-protein maize cultivars were the highest in loam among the three soils,and the yield and the protein content were the lowest planted in the sandy soil.So,the loam was the most suitable soil of high-protein maize cultivars.The order of content of 17 kinds of amino acids including lysine in high-protein maize seed planted in three soil types is the centerthe loam soil＞sandy soil＞sandy clay soil.The contents of four components of maize seeds growing in the center loam soil were higher than that in the sandy soil and sandy clay.The albumen and globulin content differences among the three soils were less than gliadin and glutenin. 8.Effect of fertilizer amount and proportion on the yield and quality of high-protein maize cultivars.The fertilizer obviously raised the yield and the protein content of high-protein maize cultivars.The effect of kinds of fertilizers was more obvious than that of any single fertilizer. The yield and protein content increased following proper increasing of the fertilizer amount. The suitable fertilizer proportion for high-protein maize cultivars was 225:112.5:112.5 kg·hm^-2of N:P:K.Applying the extra nitrogen increased gliadin and glutenin content more obviously than albumin and globulin.The nitrogen could mostly increased the content of gliadin.The change in albumin was not obvious with different fertilizer proportion.The effect of fertilizer on globulin content was more obvious before 20 d after pollination than later.Proportional nitrogen,phosphorus and kalium could mostly enhanced glutenin content,and it showed that fixed fertilizer was most benefit for impoving protein.The glutenin content was highest when the proportion of nitrogen,phosphorus and kalium was 112.5:56.25:56.25 kg·hm^-2.But too fertilizer minimized glutenin content.Applying fertilizer alleviated the decrease of the NRase activities in the ear leaf,so it was advantageous to protein biosynthesis in the ear leaf.The NRase activity in maize seeds was also high and its change trend was "S".The NRase activities increased by applying fertilizer,but the trend had no change.At the latter filling stage,applying fertilizer raised the NRase activity in maize seeds,which benefit for protein biosynthesis.Proportional fertilizer enhanced GS activities in the maize seeds at the entire filling stage.