Distribution and transport patterns of NSC in Lycoris radiata based on 13C tracing
[Objective]The objective is to analyze the synthesis,transportation and distribution of non-structural carbohydrates(NSC)in Lycoris radiata.[Method]13C isotope pulse labeling method was used to study the distribution and transport pathway of newly assimilated carbon in different organs(leaves,roots,inner bulb,middle bulb and outer bulb)and NSC components(sucrose,fructose,glucose and starch).[Result](1)The biomass and total carbon content were the highest in the inner bulb.The sink vitality of each organ in descending order was leaf,inner bulb,root,middle bulb and outer bulb.(2)After absorbing 13CO2,the distribution ratio of 13C in different organs from high to low was leaf,stem and root.The distribution in bulbs gradually decreased from inside to outside.The distribution ratio of 13C-labeled sucrose in different organs of L.radiata from high to low was manifested as inner bulb,leaf,middle bulb,root and outer bulb.The distribution ratio of 13C-labeled fructose and glucose ranging from high to low was leaf,inner bulb,root,middle bulb and outer bulb.The distribution ratio of 13C-labeled starch from high to low was expressed as leaf,inner bulb,middle bulb,root and outer bulb.(3)The transport of 13CO2 in L.radiata mainly involved two major pathways:horizontal and vertical,with 13C being transported more in vertical direction.(4)The distribution of 13C in NSC components was the highest in sucrose,followed by 13C-labeled fructose,while the content of 13C-labeled glucose was minimal in various parts,lower than other sugars.(5)In the process of sugar conversion and metabolism,the 13C distribution rate of fructose in leaves,roots and inner bulb was 9.6,41.5 and 118.1 times that of glucose,respectively.The newly synthesized fructose was much more than glucose in a short time.[Conclusion]The distribution of newly assimilated carbon in L.radiata gradually decreases in both vertical and horizontal transport.The photosynthetic products in the leaves of L.radiata are first transported to the inner layer of bulbs,and some are first transported to the roots.The other part is transported from the inner layer to the outer layer of the bulb.At this point,the middle and outer layers of the bulb mainly serve as temporary nutrient reservoirs.Sucrose is not only the main product of photosynthesis in L.radiata leaves,but also the main form of NSC transport in L.radiata.The production of a large amount of 13C-labeled fructose in L.radiata is related to the preferential use of sucrose synthase pathway in the sucrose hydrolysis process,which also elucidates the significance of illustrates that fructose for the growth and development of L.radiata.[Ch,6 fig.36 ref.]
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