| Wheat is one of the most important food crops in north China.Drought is one of the main factors that restrict the high and stable yield of wheat in China North areas.It is important to understand the mechanisms of plants adapt to water-limited conditions and select wheat genotypes better suited to drought.The effects of water stress on dry matter accumulation,translocation of ear and yield in different ploidy wheats were studied,in order to further tap the spike of wheat production potential,to lay a theoretical foundation for enhancing yield.Taking four wheat species(diploid Specie: Triticum.Boeoticum;tetraploid specie: T.dicoccoides;hexaploid species:Bima1 and Mazha)as test materials.The change of dry matter accumulation,distribution and translocation in the ear of wheat and its effect on yield were studied in the course of evolution and also studying the effect of awn on the distribution of ear and the yield components.The major results are as follows:1.In the evolution of wheat from diploid to tetraploid and hexaploid,the dry matter translocation amount,translocation ratio and the contribution rate to grain of ear before anthesis increased firstly and then decreased,the dry matter accumulation after anthesis increasing gradually and the contribution rate to grain drecreasing first and then increasing,as well as the distribution of grain dry matter increased gradually.Compared to the hexaploid and diploid wheat species,the dry matter distribution in peduncle,palea,and glume were the lowest in tetraploid wheat.Water stress increased the dry matter allocation rate of ear,the dry matter accumulation amount and the contribution rate to grain,which reduced the dry matter transportation,transport efficiency,and its contribution to grain pre-anthesis of the wheat organs in different ploidy wheats.Water stress had the minimal impact on the translocation,translocation efficiency and the contribution rate of pre-anthesis in tetraploid wheat.,2.The dry matter distribution of ear in awned wheat was lower than the awness wheat,increasing the distribution of grain dry matter.The results showed that the dry matter retention amount in the ear of the awn wheat was the least,and the dry matter transported to the grain was higher.It showed that the dry matter of organs in the ear could be transported more to grain,which laid the foundation for maintaining the yield.Water stress increased dry matter distribution of ear,reducing the distribution of grain dry matter.The results showed that drought stress could change the distribution of assimilates in different parts of the ear,and affect the transport of assimilates to grain,resulting in lower yield.The awned wheat improved the grain number per ear,1000 grain weight and water use efficiency,so it played a major role in the increase of wheat yield.Under the water stress,grain number per ear,1000 grain weight of the awned wheat drecreased smaller,and the water use efficiency increased more,indicating that the awned wheat was beneficial to the improvement of water use efficiency.3.In the evolution of wheat from diploid to tetraploid and hexaploid,above-ground biomass increased firstly and then decreased,and 1000 grain weight,grains per spike,grain yield,harvest index and water-use efficiency increased gradually.In the process of evolution,the increase of wheat above-ground biomass and yield were closely related to the increase of 1000 grain weight.Warer stress reduced the harvest index of 3 different ploidy wheats,indicating that the drought was not conducive to the transport of wheat dry matter into the grain,thus reducing the yield.The water use efficiency was improved under water stress,indicating that water stress was beneficial to improve water use efficiency.The higher yield of hexaploid wheat may be related to the higher accumulation of dry matter and the higher contribution rate to grain after anthesis.Under water stress,the yield of tetraploid wheat decreased smallest,it is possible to be associated with the minimum distribution of dry matter in the ear and the maximum translocation ratio of each organ in tetraploid wheat,the higher dry matter translocation efficiency and the lower dry matter retention amount in the ear of tetraploid wheat contributed to the increase of the 1000-kernel weight.This may be the underlying mechanism of the tetraploid wheat showed stronger drought resistance under water stress. |
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