| Camellia oleifera Abel is an evergreen shrub of the genus Camellia in the family Theaceae,which is a unique woody oil species in China as well as an important afforestation and greening species in the southern hilly areas.C.oleifera large-size seedlings are those who are more than 3 years old and have reached the large-size standard in terms of growth index.Traditionally,2-year-old seedlings have been used in C.oleifera forests.However,the growth of young forests is very slow,and the young forests are easily covered by weeds,with a low survival rate,a long time to enter the fruiting stage,and a high cost and long time for land rental and nurturing.The use of more than 3-year-old large-size seedlings to create C.oleifera forests,with seedlings strong,more branches,root system developed,fast growth,drought resistance and infertile ability,not easy to be covered by weeds,high survival rate,can shorten 2 years or even 3 years into the fruiting season,early production,significantly reduce the production costs of young C.oleifera forest nursery,is also the current and future C.oleifera seedlings production and high-yielding C.oleifera forest to create an important development direction.Three state-approved C.oleifera seedlings of`Huajin’,‘Huashuo’,and‘Huaxin’were utilized as test materials in this paper to investigate the effects of varying substrate ratios,non-woven container cups,and transplanting density on the growthand photosynthesis of C.oleifera seedlings.We studied the effects of various substrate ratios,non-woven container cups and transplanting density on the growth of C.oleifera seedlings,and identified the suitable substrate,the best container size and seedling planting density for the cultivation of 3-year-old large cups of C.oleifera seedlings,in order to provide a scientific basis for the strong seedlings of C.oleifera.The main research results are as follows:(1)Study on the effect of different substrate ratios on the growth of 3-year-old C.oleifera seedlings.Transplanting 2-year-old C.oleifera seedlings of three cultivars in seedling containers with yellow subsoil added in A1 treatment revealed that in May,August,and October,seedling height,ground diameter,number of leaves,new shoot thickness,number of branches,root length,root surface area,root diameter,and chlorophyll SPAD values were significantly lower than those in other containers with light substrate,and overall growth was weaker.The seedling height,ground diameter,number of leaves,new shoot thickness,number of primary branches,number of secondary branches,root length,root surface area,root diameter and chlorophyll SPAD values of C.oleifera ’Huashuo’ in October under A3 treatment(50%yellow subsoil+30%peat soil+20%perlite)were higher than those of A1 treatment by 24.12%,47.95%,38.83%,11.96%,97.87%,208.33%,53.33%,30.07%,7.74%and 18.21%respectively,with highly significant differences(P<0.05);Under A4 treatment(20%yellow subsoil+50%peat soil+30%perlite),seedling height,ground diameter,number of leaves,new shoot thickness,number of primary branches,number of secondary branches,root length,root surface area,root diameter,chlorophyll SPAD values,net photosynthetic rate and transpiration rate in October were 27.98%,45.21%,36.63%,16.30%,119.15%,316.67%,66.25%,40.12%,10.97%,19.76%,40.16%and 22.55%respectively,with highly significant differences(P<0.05),and non-significant differences between A3 and A4 treatments compared to each other.The comprehensive analysisshowed that the peak growth period of large-size container seedlings of the three C.oleiferacultivarswasmainly between axillary bud emergence and before May,followed by growth from May to August,and relatively slow growth after August.Through the comprehensive analysis of each index,the suitable substrate formula for 3-year old container seedlings of C.oleifera is:20%yellow subsoil+50%peat soil+30%perlite,and in later production,the proportion of yellow soil in the substrate can be increased when the transportation distance is closer in order to save the cost of seedlings from the comprehensive consideration of seedling transportation,uphill and production cost.In addition,the differences in seedling height,ground diameter,number of leaves,thickness of new shoots,number of branches and other indicators among the three C.oleiferacultivars were not obvious,and the seedling height and ground diameter of C.oleifera ’Huajin’ variety were higher than those of ’Huashuo’and ’Huaxin’ cultivars as a whole.(2)Study on the effect of different sizes of seedling containers on the growth of C.oleifera seedlings.Three cultivars of oil tea seedlings transplanted in two non-woven container cups of B1(8 cm diameter × 10 cm height)and B2(14 cm diameter × 16 cm height)showed lower overall growth than other large size non-woven container cups,and were prone to coiled roots,with the main roots penetrating the containers.The seedling height,ground diameter,number of leaves,number of primary branches,number of secondary branches,root length,root surface area,root diameter as well as chlorophyll SPAD values,net photosynthetic rate,stomatal conductance and transpiration rate of C.oleifera’Huashuo’ under B3(20 cm diameter × 22 cm height)in October were 36.76%,59.09%,36.60%,36.60%and 154.76%,430.00%,55.91%,40.12%,8.86%,20.03%,65.28%,85.25%and 120.42%respectively,with highly significant differences(P<0.05);and the seedlings under B3in October were higher than those of B1 by23.13%,31.25%,18.15%,16.50%,46.58%,89.29%,15.14%,6.17%,8.47%,32.32%,54.79%and 105.10%respectively,with highly significant differences(P<0.05).Under B4(26 cm diameter × 30 cm height),seedling height,ground diameter,number of leaves,new shoot thickness,number of branches,root length,root surface area,root diameter and chlorophyll SPAD values,net photosynthetic rate,stomatal conductance,transpiration rate and water use efficiency of the three C.oleifera cultivars were slightly higher than those of the B3 treatment,but there were no significant differences(P<0.05).Therefore,the suitable container size for cultivating 3-year-old seedlings of C.oleifera is 20 cm × 22 cm.(3)Study on the effect of different transplanting density on the growth of C.oleifera seedlings.The effect of four different transplanting densities of the same container size on the growth of 3-year-old C.oleifera seedlings was investigated in this paper,and it was discovered that the growth of seedlings under treatment C1(no gap in the middle of the container cup)was not significantly different from treatment C2,except for a significant difference in seedling height.The seedlings under treatment C2(leaving 5 cm distance in the middle of the container and filling with yellow subsoil in the middleof the container)have the highest seedling height,but the seedlings grow vigorously,and some of the roots penetrate the container deep into the soil.Compared to the seedlings under the C3 treatment(5 cm distance between containers,no yellow subsoil filling)and the C4 treatment(10 cm distance between containers,no loess filling),the root system of the seedlings under the C1 treatment is more complete and retains water and fertilizer better,producing more large seedlings per unit area.Therefore,through the test and comprehensive comparison,it was found that a constant density of 20 cm × 22 cm non-woven containers placed next to each other is suitable for cultivating large-sized seedlings of 3-year-old C.oleifera. |
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