Preliminary Researches On Tuber Formation Of Helianthus Tubersosus Land The Relation With Endogenous Phytohormones

The salt stress is one of the most serious limitations for agricultural production.It has important strategic significance to use and improve the saline lands and to increase the reserve cultivated land resources.This study focused on the biological characteristics of tuber formation of Jerusalem artichoke(Helianthus tubersosus L.).It clarified the relationship between endogenous hormones and tuber growth and discussed the rules of accumulation and distribution of main inclusions of tuber.The preliminary researches provide theoretical support for the high yield potential for the development of Jerusalem artichoke.Two Jerusalem artichoke varieties(NY-1 and QY-2)were selected as experimental materials to find the differences in tuber development and take the rules of endogenous phytohormones level in tuber.By comparing the differences between two genotypes of Jerusalem artichoke to division the tuber formation process and evaluate the effects of phytohormones to tuber growth.Based on the results,Jerusalem artichoke cultivar MY-1 was used in water-culture experiment to evaluate the relation of endogenous phytohormones and biomass by NaCl treatment.And the NY-1 tuber growth in saline soil and change rules of the of endogenous phytohormones level were studied.The results and contents are listed as follows:1.Jerusalem artichoke tuber formation mainly by phellogen produce a large number of phelloderm cells inward along with the secondary microtubule organization thin-wall organized continually,and parenchyma cells in marrow proliferated and increased at the same time.The tuber formation process of Jerusalem artichoke could be mainly divided into three stages:stolon formation and growth,Induction of tuberization and tuber initiation and tuber growth.There was a time difference in tuber development of different varieties.2.Sugar was temporary storage in the stem before tuber formation,and then transferred to underground tuber.The sucrose and fructose synthesized into fructan and stored in tuber.Tuber growth with the fructan accumulated gradually.The underground biomass accumulation and TSS accumulation rate in tubers of QY-2 were only 35.31%and 9.90%of NY-1 respectively,which is the reason of the lower tuber yield in QY-2.3.During tuber development,NY-1 and QY-2 showed the same changing rules of endogenous phytohormones.GA3 and IAA concentrations increased in stolon and then declined in tuber.While ZT and ABA increased over the whole process.The higher GA3/ABA and IAA/ABA riatos were beneficial for stolon elongation,while lower riatos promoted tuber expansion.And the GA3/ABA and IAA/ABA riatos were significantly related to sugar accumulation in tuber.4.When under salt stress,the biomass in Jerusalem artichoke of NY-1 was decreased significantly compared to control.It was clearly showed that the biomass not only in part of aboveground but also in underground all reduced observably under the treatment of 4‰ salinity,and the fresh weight and dry weight were increasing gradually with the increasing of concentration of NaCl,however,the contents of total sugar and reducing sugar in cultivar of NY-1 demonstrated shifty tendency that raised first then fell.The level about endogenous hormones of IAA and GA3 also increased first and then decreased,when the concentration of NaCl raised to 6‰ or higher,the content of ABA increased significantly.5.In NY-1,the underground biomass and sugar content in stem as well as the efficiencies of dry matter and sugar transfer to tuber declined with the soil salinity increased.Moreover,the synthesis of fructan start earlier while the fructain accumulation rate declined with salinity increased.During the formation of Jerusalem artichoke tuber,higher GA3/ABA and IAA/ABA ratios were stimulative for the elongation of stolon,nevertheless,downtrend of the ratios manifested the facilitation of tuber expansion.When treated with moderate salinity,the synthesis of IAA and GA3 were inhibited significantly,but an opposite phenomenon emerged in the synthesis of ABA.These results suggested that the tuber formation of Jerusalem artichoke were the transportation of aboveground dry matter and the fructan accumulation.It was closely related to endogenous phytohormones levels.The growth of seeding and tuber under salt stress were adjuted by endogenous phytohormones.