| Phoebe sheareri is a unique precious timber tree species in China.In order to explore the dormancy type of Phoebe sheareri seeds,improve the seed germination rate,and study the best N,P,K fertilization formula for the growth of Phoebe sheareri container seedlings.In this paper,by measuring the permeability,air permeability and germination inhibitors of the seeds of Phoebe sheareri,the causes of seed dormancy were explored and the types of dormancy were determined.The method of breaking dormancy was studied by low temperature stratification.The temperature suitable for seed germination was studied by setting 7 temperature treatments:15 ℃,20 ℃,25℃,30℃,35℃ constant temperature,30℃ night 20℃,25℃ night 15℃variable temperature.At the same time,this experiment used 1-year-old container seedlings of Phoebe sheareri as materials,and set up 18 different N,P,K formula fertilization groups.By measuring the growth,physiology,nutrient content and photosynthetic characteristics of Phoebe sheareri container seedlings,using seedling quality index analysis,principal component analysis,membership function analysis and other comprehensive analysis and cvaluation methods,the best fertilization formula for Phoebe seedlings was screened in N,P,K formula fertilization.The main findings are as follows:(1)Fresh seed coat has obvious water absorption and respiratory barriers to seeds,and has the characteristics of physical dormancy.The germination rate of 60-day peeled seeds is about 31 times that of intact seeds.The seeds of Machilus thunbergii contain water-soluble and alcohol-soluble endogenous inhibitors,which have the characteristics of physiological dormancy.Therefore,it is determined that Machilus thunbergii is a comprehensive dormancy(physical dormancy and physiological dormancy).(2)Low temperature stratification can break the dormancy of Phoebe sheareri seeds.With the extension of low temperature stratification time,the germination of seeds was earlier,the germination rate was accelerated,and the germination rate was increased.The germination rate of seeds with low temperature stratification for 100 days was significantly higher than that of other treatments,up to 98.89%.The effect of GA3 soaking on breaking seed dormancy was not ideal.25℃ is the optimum temperature for germination.(3)Among the growth indexes of each fertilization treatment group of Phoebe sheareri container seedlings,CK growth was the worst,G10(18.28cm)seedling height was the best,61.77%higher than CK;g10(4.98mm)had the highest ground diameter,which was 144.10%higher than CK.G10(32.22cm2)had the largest leaf area,which was 3.37 times that of CK.The total biomass of G10(5.15g)was the largest,which was 6.5 times that of CK.G10(N2P2K1)performed best in growth indicators.(4)The total root length of G10 was 730.97 cm higher than that of CK.The root surface area was 6.59 times that of CK.The total root volume was 7.03 times that of CK.The highest average root diameter was G12(0.89cm),which was 33.35%higher than CK.Except that the average root diameter was the best in G12(N2P1K2),the other three indexes were the best in G10(N2P2K1).(5)Among the nutrient element indexes of each fertilization treatment group,the effects of nitrogen,phosphorus and potassium formula fertilization on the nutrient elements of Phoebe sheareri container seedlings:N,P,K,Ca and Mg were different.Among them,the highest total cumulative content of nutrient elements in roots,stems and leaves was G10,containing 43.40 mg·g-1,39.35 mg·g-1 and 46.67 mg·g-1,respectively,which was 66.41%,78.85%and 36.69%higher than CK,respectively.(6)Among the physiological indexes of each fertilization treatment group,the contents of soluble sugar and soluble protein in each fertilization treatment group were all higher than CK,June,August,October generally showed a trend of rising first and then falling.The soluble sugar content of G12,G15 and G10 in June,August and October was 69.66%,84.74%and 79.73%higher than that of CK,respectively.The soluble protein content of G13,G12 and G10 in June,August and October was 55.99%,71.08%and 63.64%higher than that of CK,respectively.The highest malondialdehyde content in G9,G12 and G10 in June,August and October was 11.71%,25.26%and 15.09%lower than that of CK,respectively.Fertilization can affect the accumulation of soluble sugar and soluble protein nutrients,reduce the content of malondialdehyde,and help to maintain the normal physiological activities of seedlings and promote growth and development.(7)Among the photosynthetic indexes of each fertilization treatment group,chlorophyll content,net photosynthetic rate,intercellular CO2 concentration and stomatal conductance showed a trend of increasing first and then decreasing,while water use efficiency showed an opposite trend.The chlorophyll content of G12,G10 and G10 in June,August and October was 17.24%,44.69%and 41.27%higher than that of CK,respectively.The net photosynthetic rate of G6,G10 and G15 in June,August and October was 67.81%,53.36%and 26.19%higher than that of CK,respectively.The highest water use efficiency of G17 and G15 in June and August was 51.16%and 82.20%higher than CK,respectively.(8)There is a certain correlation between the indicators of each fertilization treatment group,and some indicators are significantly correlated.According to the results of seedling quality index analysis,comprehensive score of principal component analysis and membership function analysis,the ranking of the better fertilization treatment groups obtained by the three analysis methods is roughly the same.Compared with the other two comprehensive analysis methods,the analysis method of seedling quality index can save time and manpower cost,and quickly obtain the optimal fertilization treatment group of Phoebe sheareri container seedlings.Therefore,the comprehensive analysis results showed that G10(N2P2K1)was the best fertilization treatment group in this experiment,which was N:2.8g·plant-1;P:0.8g·plant-1;K:0.5g·plant-1. |
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