Transportation And Partitioning Of Photosynthate In ‘Relay’ Grain-filling Wheat

The grain filling model of inverse leaf aging sequence(ILAS) is called ‘relay’ grain filling model,which is different from traditional wheat grainfilling. ILAS wheat has a certain proportion of tillers of which flag leaf senesced earlier than penultimate leaf in late grain filling stage. Although traditional wheat breeding theory considers that early senescence of flag leaf is an adverse phenotype to wheat yield and mainly focuses on the physiology of flag leaf, ILAS wheat was reported having a higher yield than normal leaf aging sequence wheat. To explore the grain filling characteristics of ILAS wheat and translocation and partition of its assimilates. ILAS wheat Lankao ai zao 8、Yumai19、Xinmai13 and normal leaf aging sequence wheat cultivar Xiaoyan22、Shan229 was chosen as materials. Dry matter weight of thousand grains during grain filling period was recorded and was fitted to Logistic equation. Dry matter weight and chlorophyll content of top two leaves was also measured to indicate its dynamics of physiological status. To estimate the contribution of top two leaves to the dry matter accumulation of kernels, flag leaf or penultimate leaf was treated by shading with hand made cloth bag. Shading treatments were set at two different levels, namely 5-day and 10-day shading. Dry matter weight and volume of grains per ear, dry matter weight of peduncle and penultimate internode of shading wheat were measured. The results are as follows:1.The dry matter weight of grain and grain filling rate of ILAS is higher than normal leaf aging sequence. Flag leaf shading and penultimate leaf shading can affect the grain filling rate and dry matter weight of grain increase. Flag leaf shading affect grain filling and dry matter weight of grain more than penultimate leaf shading for normal leaf aging sequence. In early filling stage,ILAS is consistent with normal leaf aging sequence,but during late filling stage is in contrary.2.Shading treatments restrain dry matter of the culm-sheath during early filling stage,but it is contribute the dry matter of the culm-sheath during late filling stage. The dry matter of the culm-sheath of ILAS were higher than normal leaf aging sequence during early filling stage, export dry matter of the culm-sheath of ILAS were higher than normal leaf aging sequence during late filling stage.3.The chlorophyll contents of top-two leaf and grain volume of ILAS is higher than normal leaf aging sequence when top-two leaf shading or not.4.The reasons of higher yield of ILAS is because of the higher capacity of photosynthetic assimilation and the higher accumulation and re operation of dry matter of the culm-sheath.