| Title: Transport and partitioning mechanism of assimilates in hybrid wheat.Supervisor: Professor Gaojunfen Ph.D Candidate: Gong yuehuaThe approaches on the sink-source relationship of crops in recent years provioded that either source strength, flow availability or the characteristics of sink itself would affect the transportation and the partitioning of photo assimilates, and thus the final yield. K-type hybid wheat 901 has the the following characteristics: long functionate duration of leaves, strong assimilatibility,green leaves and shoot in the end of growth stage.Accordingly, the present paper used hybrid wheat 901,the father plant R205 and the mother plant K3314A,the general plant Shan229 and Xiaoyan22 as experimetal materials,to study the characteristics of the sink,flow and source after anthesis using pot and field experiments from 1997 to 2000.The purposes for this study were to reveal the transport and partitioning of assimilates,and the mechanism of assimilates left in the source area in hybrid wheat 901 during the end of growth stage.After anthesis,the net photosynthesis speed(Pn),the transpiration speed and the size of flag leaves, and the content of chlorophll and carbohydrates in flag leave were determined.The results showed that the Pn of the hybrid wheat was lower just after anthesis,but higher than that of the controlled plant during the mid- and end of the filling stage,having priority in this aspect. Also, the leaves of 901 had a larger size,its chlorophyll content lowered slowly,and the functionate duration of leaves was longer. As a result,in the middle and the end of filling stage, the source leaves could provided enough assimilates for utility.However, in the end of filling stage,the content of starch in the leaves of the hrbrid wheat was high,and much available carbohydrates reserved were left in the leaves while the matter in the leaves were exported slowly.All these showed that much photoassimilates were not export and left in the souruce leaves.This was closely related to the characteristics of the father plant.Wax slicing technique and micro-structure determination methods were adopted to study the vascular bundle structure in flag leaves,sheath,internodes,the 1st node below the ear,rachis of hybrid wheat 901,the father and mother plant,and Shan229.The results showed that the numbers and the area of vascular bundle in the above tissues of hybrid wheat 901 and its father plant were larger than Shan229.These might be the structure basis for 901 yeilding larger ears,many spikelets and many glumiflorous.However, the vascular bundle area in kernel crease tissues of 901 was the smallest,and thiswould be one of clues why the kernels of 901 were slowly filled in the end of filling stage. The ultrastructure research in source loading area and sink unloading area and the histochemical research of ATPase activity in source loading area both revealed that no apparent difference occurred in four experiment materials.The sizes, water content.the accumulation speed of dry matter weight of kernels, and the content of total soluble carbohydrates(TSC), sucrose and starch in the wheat kernels were determined.The results indicated that, during the formation stage of kernels,hybrid wheat 901 grew more quickly in cell expansion of kernels, and the size increased faster,but during the middle and the end of the filling stage the filling speed became slower with the filling time lasting longer. While TSC and sucrose being the substrates for starch formation.the changes of their content in kernels were strongly related with that of the starch accumulation speed and the filling speed. The changes of enzyme activities which dissoluted the sucrose showed that the invertase activities mainly played a role during the kernel formation stage, and the sucrose synthase activities were the highest during the time when starch began to accumulate quickly.This proved that the sucrose synthase had a key role in sucrose degradation during the transformation of sucrose to starch.The lower...
|
PDF Full Text Request