Effects Of Nourishment On The Physiological Character In The Process Of Tuber Formation In Solanum Tuberosum L.

Potato ranges the forth of food crops in the world while it is increasing importance in Chinese food,vegetable,feed and processing.However the unit yield and production level are low and the cultivation technique is lacking today than those of developed countries.So it is very significant to study the high-yield culture techniques in order to improve the potential of production and increase the economic benefit.It is also important to promote the market competitive power in the world,to assure the food safety in our country and to raise the comprehensive economic benefits in agriculture,so it can push the processing industry of potato enter a new stage in the country.In order to reveal the mechanism how nutrients promote tuber development under different nutritional levels,the flesh-edible potato,high yielding variety,high-starch and low-starch content potato have been used as experiment materias.The first objective of this study was to reveal the changes of endogenous hormones,polyamines(PAs),yield and quality in the process of tuber development in potato(Solanum tuberosum L.)under different nutrition.The second objective was to analyse the the dynamic accumulation of starch,amlose and amylopectin and to determine the patters of the actives of key enzyme involved in starch synthesis and to find the relationship between the accumulation of starch and key enzyme in the process of buberization uder different levels of nitrogen.The third objective was to discuss the characteristic of photosynthesis and chlorophyll fluorescenceS under different nutritional conditions in order to reveal the mechanism how nutrition influence the photosynthesis of potato.The expected results would help understand the mechanism how nutrients affect the tuber development and obtain a new technique of high yield.The main results are as follows:1.In tuber development,under- or over-supply of nutrients reduced ZT content at initial stage and IAA,ABA and JAs content at middle stage,but increased GA₃ content in the whole process,which caused GA₃/ABA and GA₃ /JAs to be off balance in the key stage of tuberization.Appropriate nutrient supply kept higher ZT content at initial stage and higher ABA,JAs and IAA content and lower GA₃ content at middle period,which could satisfy the demand of important hormones in every stage of tuberization and keep GA₃/ABA and GA₃/JAs at reasonable levels during tuber formation.2.The contents of three kinds of PAs(put,spm and spd)have two peak values at early and middle stages in the tuber development respectively,comforming with the trend of decrease-increase-decrease.However the contents had different respondenc to different fertility levels.In middle stage of tuberization PAs contents under moderate fertility level were higher than that under low and high fertility levels.High fertility made the put content decrease,the peak time of put advance,and the peak time of spm and spd postpone. With the increase of fertility the peak value of put/spd reduced continuously and the peak time advanced.Under low fertility level JAs content was low in all stage.And in the middle stage the JAs content under moderate level was higher than those under low and high fertility levels.The GA₃/JAs under low and high fertility levels increased firstly and then decreased.The change trend was reverse to that under the moderate fertility level.JAs content had significant positive correlation with the content of put,and significant netive correlation with the contents of spd and spm.3.The photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO₂ concentration(Ci)of potato showed a single-peak trend with the amount of nitrogen increasing.As far as responsing to the light quantum flux density(PFD)and CO₂,the Pn showed the similar trend.To the nitrogen nutrition on the characteristic of light and CO₂ demand of potato,the maximum net photosynthetic rate(Am),the apparent quantum efficiency(Ψ),CO₂ saturation point(CSP)increased at first with raising of nitrogen levels then diecreased with further nitrogen enhancement At the effects of nitrogen on the chlorophyll fluorescence characteristics,the actual photochemical efficiency of PSâ…¡(ΦPSâ…¡),photochemical fluorescence quenching(qP)and electronics trancelation rate(ETR)showed of the same changes.4.There were some differences in the use of light energy at different varieties of potatoes.To the high-starch varieties QS2,the stomatal conductance(Gs),transpiration rate(Trmmol),photochemical quenching factor(qP),non-photochemical quenching factor(qN)and CO₂ saturation point(CSP)were higher than the low-starch variety C117 in the same level of nitrogen.Furthermore the light use efficiency(LUE)and net photosynthetic rate(Pn)also had more advantages than the low-starch variety C117. However to the low-starch varieties C117,the efficiency of water(WUE),the light saturation point(LSP),the light compensation point(LCP),the CO₂ concentrations point(CCP),the potential photochemical efficiency(Fv/Fm)and actual photochemical efficiency(ΦPSâ…¡)were higher than the high-starch variety QS2 under the different conditions of nitrogen fertilizer.At the same conditions of nitrogen,the maximum net photosynthetic rate(Am)of C117 was higher than the QS2 in different concentration of CO₂.However,the light use efficiency(LUE)and photosynthetic rate(Pn)of high-starch cotent variety was higher than the C117 at NO,N1,N2 levels of nitrogen,expressing a stronger ability of using light.5.The amylose,amylopectin and starch content(the sum of amylose and amylopectin content)increased in "S" curve fashion in the process of tuber development under different levels of nitrogen,and the curves satisfied the Logistic function of Y=K/(1+ae^-bT),but the greatest accumulated intensity and the time reaching the peak exsisted difference at different levels of nitrogen and different varietyis of potato.For the low-starch variety C117,with the increasing of nitrogen nutrient,the greatest accumulation intensity of amylose showed decling tendency,and the amylopectin showed the increasing trend while the starch showed increasing until reach the peak then decreasing.The time of reacing the gretest accumulated intensity of amylose and starch esist the trend of increasing at first and then decreasing,but the amylopectin showed the decreasing constantly.For the high-starch content variety of QS2,the gretest accumulated intensity of amylose were lower with middle level of nitrogen than that of low and high level of nitrogen,but the trend of amylopectin and starch increasing at first and then decreasing with increasing of the nitrogen levels.As a result the amylase,amylopectin and starch content of QS2 were lower than C117,not reading it's potential of stach accumulating as a high-starch variety under the circumustance in Sichuan.6.In the process of tuber development,all of the ADPGPPase,SSS,GBSS,SBE content increased constantly after reaching the maximal then decreasing until the last, showing the single peak trend at every nitrogen level and reaching a stationary phase of maxismal content at 54-61 days after emergence of seeding.As far as to the effects of nitrogen on key enzyme,the ADPGPPase,SSS showed the same changes of single peak trend,but for the influence of the GBSS and the SBE,different varieties had different results.The content of the ADPG-PPase,SSS of low-starch variety of C117 was higher than the high-starch content variety of QS2 under each nitrogen levels,showing the significant activety.At the influence of nitrogen nourishment on correlation of the enzymes and starch accumulation,the SSS activity was significantly and positively correlated with the starch and amylopectin content(r_starch=0.86^**,r_amylopectin=0.83^**),but was not significantly and positively correlated with the the amylose content.7.The result of nitrogen application on potato showed that all of the base fertilizer and the topdressing of nitrogen were important on yields of the springs potato,especially to the topdressing,and the yield increased more obviously than the base fertilizer.But for the autumn potato,the function of base fertilizer was more important than the topdressing of nitrogen on the yield,and the action of topdressing was absent.So in order to obtain the high yield of spring potato,we should think much of topdressing besides the base fertilizer, but for the autumn potato,it should play important role of base fertilizer,and topdressing of nitrogen should be specially cautious.