| The phosphorus of southern acidic soil is ease fixed by iron,aluminum and other metal ion,so it cannot be used by plants.Lacking of effective phosphorus is the one of limited factors for plants growth.In long-term evolution process,some plants formed a series of physiological and biochemical mechanisms to response to low phosphorus stress environment.Chinese fir is one of the main afforestation species in south China.The low available P in soil is an important factor of restricting southern Chinese fir growth.Calcium ion as the second messenger in cell could be participated in response to low phosphorus stress,and could induce morphological and physiological responses of plants.Many scholars did qualitative analysis pH changing of rhizosphere micro area by agar instructions statutory or acid-base neutralization titration methods.They considered that fir root can increase rhizosphere acidification ability to use environment difficult soluble phosphorus by secreting protons.But these traditional methods are hard to measure the dynamic proton quantitative accurately,and difficult to reveal the internal mechanism of Chinese fir response to low phosphorus stressIn order to solve this problem,the paper applied simulated low phosphorus environment method,with different Chinese fir families as the research object.On the basis of the preliminary screening different phosphorus-use-efficiency Chinese fir,used Non-invasive Micro-test Technique which could obtain the real-time,dynamic ion flow velocity and direction information of sanples to study difference between H+or Ca2+secretion and of different phosphorus-use-efficiency Chinese fir under phosphorus stress.Through the accurate measurement information of tissue and cell ion balance,trying to clarify the relationship between internal control mechanism and the root proton and calcium flux under low phosphorus stress,discussing the correlation of ion flux and phosphorus utilization characteristics.In order to provide scientific basis of the internal mechanism and adapt to phosphorus stress of Phosphorus use efficiency Chinese fir.The main results were as follows:1.There were obvious difference of 10 Chinese fir families in seedling height,root growth situation,biomass,the amount plant phosphorus accumulation and phosphorus efficiency under phosphorus stress.The root of No.28 were growth well in phosphorus deficiency,root extension and root surface area increased.The quantity of phosphorus accumulation was minimum reduction,and the ability of resistance to enhance phosphorus starvation by improving phosphorus use efficiency significantly.Both of root extension and surface area increased were receded of No.32,the varied range of phosphorus accumulation was bigger,but the change of P utilization rate was not obvious in the case of phosphorus deficiency.NO.32 mainly regulated their own growth speed to adapt to low phosphorus environment.2.Proton flux were significant difference in each part of the root,the net ions flux of root tip was the highest,but no significant difference between other parts.The rhizosphere pH had a slightly upward trend in NO.28 and NO.32.When under phosphorus deficiency,the variations in the rise of rhizosphere pH values were less than normal phosphorus levels.The H+flux direction and velocity of the different root parts were different,which leaded the absorption of anion and cation out od balance and changed rhizosphere pH eventually,this change distribution in root tip to the root apex almost root surface.There was 0-0.2 units difference in rhizosphere pH,and the root apex part increased nore pH value than the root tip.3.Tine of H+absorption peak were difference between two Chinese fir families,NO.32 had no obvious absorption peak,but NO.28 appeared absorption peak at 8th days.With the extension of processing time,compared with normal phosphorus controls,the H+net flux had no significant differences of NO.32,while the H+ net influx of NO.28 conformed to enhance to weakened regularity trend.Visible,root proton flux changes with the selected varieties of fir and the length of the processing time,and two Chinese fir families had no consistent in change of H+.4.In soluble phosphorus environment,some root parts had a little amount of protons outflow of NO.28 and NO.32 at 3th day under phosphorus stress,but were not observed protons outflow at 8th,15th day.This may be related to half-life of H+-ATPase and intermittent absorption of phosphorus.In the difficult soluble phosphorus environment,the protons were influx of NO.28,but NO.32 had H+outflows in two parts of root after dealing with 3 d.visible,under the difficult soluble phosphorus system,NO.32 had a strong ability to difficult soluble phosphorus utilization.5.With the increase of phosphorus concentration,H+net flow were continuously reduce in root tip and apex of two families,but the direction of H+ flow had not been changed.The H+variation trend had no difference between root tip of 2 families.No.32 was relatively flat,but No.28 had a great change.Both of them tended to stable state finally.The variation trend in root apex was different from root tip,which was obvious volatility,the H+variation trend of two Chinese fir families were opposite.Visible,proton flow related to the varieties of Chinese fir and part of root.H+/Pi synthetic transporter protein,H2PO4-/2-4H+ co-transport and dynamic balance of phosphorus in the cytoplasm may affect.the response of different Chinese fir6.The instantaneous change of Ca2+was related to Chinese fir varieties,phosphorus concentration and part of root.With the increase of phosphorus concentration,calcium in root cell had almost the same trend in root tip of No.28 and No.32,the trend was as follow:rise-fall-rise-steady state,Ca2+outflow both reached peak when added 0.1 mmol·L-1 KH2PO4 instantaneously.Ca2+flux in root tip cell of No.28 were greater than No.32,Ca2+outflow at a higher level.Ca2+outflow of No.32 weakened and eventually changed the direction when added 0.1 mmol·L-1 KH2PO4 instantaneously.Ca2+flux in root apex of two families were difference and showed the opposite trend after adding 1.0 mmol·L-1 KH2PO4 instantaneously.In the whole test process,Ca2+od No.28 were sustained outflow,both of root tip and apex hadt the same trend,while No.32 was different,both of root tip and apex had changed the original direction,but the duration of this phenomenon was shorter.Visible,Ca2+ was involved in plant perception and response tolow phosphorus stress process,and this process was associated with varieties of fir and phosphorus concentration,intracellular Ca2+ increasing was a transient process.7.When KH2PO4 was added to the environment instantaneously,the H+instantaneous net flow in maturation and immaturation zone of fir root and phosphorus concentration had significantly positive correlation.,but Ca2+flow had no obvious rule.The outflow of Ca2+and H+influx had a weak negative correlation in root tip,the outflow of Ca2+and H+influx had a weak positive correlation in the maturation zone.Ca2+and H+ reversed transportation,promoting the inflow of H+,causing apoplast basification and cytoplasm acidification,which might cause root apex pH value increase greater than the root tip. |
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