Response Of Different Cunninghamia Lanceolata Under Atomized Low-phosphorus Stress Environment

Phosphorus(P)is an essential element for the growth of trees,which is the composition of many important compounds such as nucleic acids,cell membranes and ATP.It plays an important role in the process of plant photosynthesis/respiration and enzyme transport regulation.However,Phosphorus is poorly migrated in soil and highly heterogeneous in the acid soil,because the strong chemical fixation of P in the south of China.The available P content of trees is low,while it could be easily lead to forest growth was inhibited.Cunninghamia lanceolata is an important fast growing and tree species in the south of China.The decline of yield of Cunninghamia lanceolata plantation is becoming more and more obvious due to the long-term multi-generation planting.The available P is extremely deficient is one of the most important factors limiting the yield of Chinese fir plantation.In the long process of evolution,Different plants had formed different strategies for adapting to low phosphorus stress,which to increase the chances of completing the lifecycle in Phosphorus deficiency environment.When the phosphorus resources are insufficient in Plants,which couldn’t meet the nutrient requirements of the plant to complete the life cycle,plant root growth is significantly blocked,the ability of the root to capture P from the soil is weakened.Under these conditions,how to fully tap the potential suitability of Chinese fir in low phosphorus stress adversity,especially the fir roots to find the capture P element and accelerated the use of P in the plant,which have great ecological significance for improving rhizosphere phosphorus availability and promoting the efficient use of plants for effective P resources.The current research on phylogenetic response mechanism of Cunninghamia lanceolata adaptation to low phosphorus stress,which using soilless cultivation mode include sand cultivation or hydroponics,but observing the root system in sand cultivation inconveniently;The water-gas-fertilizer three-phase is also difficult to control.Nutrient solution dissolved oxygen concentration is limited in hydroponics,poor plant ventilation and plant easily rot is also in it.Spray Culture had emerged in recent years,which is a new soilless cultivation mode to place the plant roots in the aerobic environment for growth and development completely.The plant root growth without the soil,substrate environment and other mechanical resistance in the aerosol environment.In aerosol cultivation,the roots stretch freely to facilitate observation、oxygen intake is rich、moisture absorption evenly、adequate supply of mineral nutrients,that provide a water-gas-fertilizer three-dimensional root domain environment for high-quality fast-growing plants.However,the application of aerosol cultivation technology is limited to crop production and research,sightseeing and display of modern agriculture and other fields currently,application of aerosol cultivation technology in forest seedling cultivation is not yet visible.In view of this,the paper selected the fast-growing fir seedling in the state-owned forest farm of Zhangping in Fujian as the reference material which had investigated by the instructor group for many years.We used self-designed forest-type atomization cultivation device,on the basis of screening for atomized cultivation conditions suitable for the growth of Chinese fir families,we had designed different atomized phosphorus stress environment,comparing the morphological and physiological changes of different Chinese fir families in atomized low-phosphorus stress environment,exploring the response mechanism of different Chinese fir families on the atomized low phosphorus stress environment.To provide theoretical reference for further revealing adaptive strategies of different P use efficiency of Chinese fir genotypes in atomized low P environment.Main results were as follows:(1)The effects of different atomization and intermittent treatments on the growth of Chinese fir seedlings were different.The average survival rate、the new root system rate、the average seedling height and diameter of the M25 families in the four fir families was the highest,and significantly higher than other families during the atomized stage Ⅰ;Compared to atomized stage Ⅰ,the indexes of M4 and M10 family in four fir families were significantly improved during the atomized phase Ⅱ,M25 family of the indicators were still the highest compared to other families.The growth characteristics of the fir family are better in the atomized phase Ⅱ,which proved Chinese fir growth was more appropriate in the relative temperature(20-28℃)humidity(100%RH),nutrient liquid droplets relative to the stagnation time(≥1.5min)in the cultivation environment,a single atomized solution(20min),intermittent(130min)within the atomized time.(2)There were no significant differences in SPAD,FM,FV,FV/FM,FV/F0 between the four fir families M4,M10,M24 and M25 at different stages of processing time atomization.M4 and the other three families F0 value difference significantly at the different working hours of the atomized stage.Accompanied by the extension of a single spray interval time,M4,M10,M24 family of F0,FM values showed a downward trend,that indicated the appropriate P element is conducive to the electron transfer of PS Ⅱ;M10,M24,M25 family of FV/F0 values were on the rise,that indicated the appropriate P level is conducive to the original PS Ⅱconversion efficiency.(3)The root length、root surface area、root mean diameter and root volume increment of six Chinese fir families were significantly different(p<0.05)in the atomization of different phosphorus treatment.The root of M4,M28 had extended and root surface area increased ability to be increased in the case of P deficiency,root length of M1 was relatively reduced,and root surface area was increased;M28 fir had the highest average root diameter increment,while M10 roots had the lowest average root diameter.In the environment of atomized P stress,with the increase in P stress levels,the root volume of M4 family increased significantly,root volume increment of M1 reduced significantly,that indicated there are different in the response mechanism of Chinese fir genotype with high P efficiency under the conditions of atomized P stress.(4)There were differences in the SPAD values of different Chinese fir families in the atomization of different phosphorus treatment.The SPAD values of M32 family reached a significant level(p<0.05)between three different treatments for P;compared with the atomization normal for P,the SPAD of M1 reached the highest value in the mild P stress treatment,the SPAD of M4 was highest in the case of moderate P stress treatment.Under the conditions of atomized P stress,Two Cunninghamia lanceolata may increase the Chlorophyll content of Plants by increase the leaf thickness,and expand the unit leaf area.With the increase of P stress gradient,the SPAD of M24 showed a gradual reduction trend at different levels of phosphorus treatment,while SPAD values of M28 showed a trend of descend first and then rising,that may be related to plant nutrient imbalance due to the absence of P element in aerosol environment.(5)There were differences in the impact that atomization of different phosphorus stress treatment on Chlorophyll fluorescence parameters of Chinese fir.With the strengthening of the degree of P deficiency,M1,M10,M28 fir family F0 value,FM value,FV values showed a trend of first rise and fall,indicating the appropriate level of phosphorus,is conducive to the PS Ⅱ electronic transmission;M32 family of FV/F0 changes in the trend of the first rise after the downward trend,this may be due to the lack of phosphorus is not conducive to PS Ⅱprimary light energy conversion efficiency.The maximum photochemical efficiency FV/FM and the initial light energy conversion efficiency(FV/F0)of M1 and M4 fir families showed an increasing trend.Indicating that the PS Ⅱ activity of the fir family with high efficiency was not significantly inhibited,and the degree of openness of PS Ⅱ was relatively high.(6)Under atomization of different P stress levels,The differences in the activities of SOD,POD,CAT and MDA were all significant(p≤0.001)in the different parts of Chinese fir.Under each of the gradient P of different organs of different Chinese fir families,SOD presented a general leaf>stem>root;POD was generally expressed as leaf>root>stem;CAT on the whole showed the roots>stem>leaves.The activity of SOD,POD and CAT in M32 family was significantly enhanced with the increase in P stress levels,which indicated Chinese fir with different P efficiency may have activated the protective enzyme system to adapt to low P stress environment.The activity of SOD,POD and CAT in M4 family decreased under atomization of different P treatment,this may be related to the genetic characteristics of Chinese fir genotypes.