Study On The Relationship Between Photoassimilates Allocation And Freezing Tolerance In Arabidopsis

Dry matter is the final product of photosynthesis.The allocation of photosynthetic products in different organs not only affect the plant's own growth and development,but also directly affect the level of food production and grain yield.At low temperatures,the mechanism of plant photosynthesis distribution has not been elucidated.In this paper,Arabidopsis thaliana was used as the material to study the effect of low temperature stress on the allocation of photosynthetic products and its relationship with frost resistance.The SUT4 gene is overexpressed in Arabidopsis thaliana and revealing the influence on the plant frost resistance and soluble sugar content.These results laid solid foundation for further study of the role of the gene in the distribution of photosynthetic products.This paper has done the following aspects of research:(1)Using Arabidopsis thaliana wild type as the material,we use a modified hydroponic method to cultivate low-cost,large-scale,well-grown Arabidopsis thaliana.Hydroponic method is very convenient to the underground part of the sampling and suitable for the overall level of research allocation of Photoassimilates in Arabidopsis.(2)In order to study the distribution of photosynthetic products at different culture temperatures,we used hydroponic Arabidopsis as material,the shoot to root ratio(S/R)was measured at 22/22 ?,22/12 ? and 16/16 ?.It was found that the inhibitory effect of low temperature on the root biomass is greater than that of shoot at 22/22 ? and 16/16 ?.And in the 22/22? and 22/12?,the S / R value of cold temperature for 2 days is reduced,indicating that the inhibition of low temperature on the shoot biomass is greater than that of the root.At 4 days,the S / R value increased,and inhibition of the low temperature on the root biomass was greater than that of the shoot.(3)The wild type of Arabidopsis thaliana was used as a material,treated after 22/22?,22/12? and 16/16? three temperature mode,we measured the carbohydrate content.The results showed that the low temperature at 22/12? could increase the soluble sugar content in plant leaves and keep the starch content at a certain level.While the soluble sugar in the roots increased first and then decreased at low temperature at night,which was opposite to that of starch in roots.While the leaves of starch at 22/22? accumulated 6 ug / mg,the accumulation content of root was 2 ug / mg.At 16/16 ?,the leaf starch accumulated 0.5 ug / mg,3.9 ug / mg starch was degraded in the root,indicating that the low temperature during the day seriously hindered the accumulation of leaf starch and accelerated the degradation of starch in the roots.While the soluble sugar at the 22/22 ? in the accumulation of leaves was 1.8 ug / mg,the accumulation of root was 9.5 ug / mg.At 16/16? low temperature leaves accumulated 6.5 ug / mg,the root accumulated 0.8 ug / mg.It was indicating that the low temperature during the day increased the accumulation of soluble sugar in the leaves,reducing the accumulation of soluble sugar in the roots.It is shown that low temperature affects the content of carbohydrates in roots and leaves.(4)In order to study the effect of different temperatures on the photosynthetic capacity of the source tissues,we measured the photosynthetic parameters and fluorescence parameters of the Arabidopsis thaliana leaves at 22/22 ? and 22/12 ?.The results showed that the photosynthetic rate of Arabidopsis thaliana decreased by 0.85 umol CO2.m-2.s-1 at low temperature.The q P and q N at 22/12 ? were lower than 22/22 ?.It was indicating that photosynthetic activity and photo protective ability of plants decreased at low temperature,and the low temperature affected the photosynthetic rate.(5)In order to study the effect of culture temperature on frost tolerance,we analyzed the low temperature semi-lethal temperature(LT50)of wild type Arabidopsis thaliana at 22/22 ?,22/12 ? and 16/16 ?.The results showed that the LT50 of the leaves was lower than that of 22/22 ?,and the LT50 of the roots was higher than that of the room temperature at 22/12 ? or 16/16 ?.The leaves at 22/12? and 16/16 ? in the temperature mode were more resistant to freezing than the 22/22? normal temperature mode,while the frost tolerance of the roots was lower than that of the 22/22? room temperature model.In summary,the low temperature affected the frost tolerance of leaves and roots.(6)In order to study the effect of SUT4 gene on photosynthetic product allocation and frost tolerance,we cloned and identified homozygous Cb SUT4 and At SUT4 transgenic plants.The results showed that Cb SUT4 is strongly up-regulated and At SUT4 changes a little respond to cold and either N-terminal and C-terminal labeled YFP,the encoding protein are both located on the plasma membrane.The transgenic plants were treated with low temperature and found sugar-free condition promotes the Cb SUT4 transgene root elongation.The soluble sugar of leaves of transgenic plants is decreased,however,the soluble sugar content in roots is increased,and also the freezing tolerance of transgenic plants of leaf is decreased at low temperatures.Low temperature stress affects the distribution of photosynthetic products,which in turn affects the frost resistance of plants,and its specific adversity adaptation mechanism needs further exploration.Low temperature affects the distribution of sugar content and freezing resistance in transgenic plants.To study the distribution mechanism of photosynthetic products at low temperature is of great theoretical and practical value to cultivate resistant and high yield crops.