| Bryophytes are endowed with highly landscape value due to its special morphological structure and physiological adaptations which has been transformed into the research hotspot of gardening and afforestation in recent yeas.Because of the deficiency in cultivating and propagating technology,the moss gardening develops relatively slowly.Leucobryum juniperoideum was considered to be an excellent ornamental bryophyte,but the mechanism underlying its propagation and growth is poorly known.For revealing its population distribution patterns,habitat types and limitation factors of introduction,its habitats were investigated in the Tianmu Mountain National Nature Reserve.For revealing the ecodaptation of L.juniperoideum,the experiments on its main limitation factors were made in laboratory from 2009 to 2013.In order to offer guidances and suggestions to its introduction,the cultivation and propagation methods were researched in the greenhouse.The main results of this paper were summarized bellow.1.The populations of L.juniperoideum were distributed in elevations from 317 m to 1292 m in the Tianmu Mountain National Nature Reserve.There are three population distribution types,i.e.the epigeic populations,the epixylous populations and the epilithic populations.There also are three main habitats,i.e.the Phyllostachys heterocycla var.pubescens(moso bamboo)dominated forest,the Cryptomeria fortunei(Chinese cedar)dominated needle and broad-leaved mixed forest,and the Cunninghamia lanceolata(Chinese fir)dominated needle and broad-leaved mixed forest.The epigeic populations of this bryophyte only occurred in areas with moso bamboo forest,while epixylous populations and the epilithic populations occurred in all three habitat types.The soil chemical analysis showed that the content of nitrogen(N),phosphorus(P)and potassium(K)in the Chinese fir forest and the Chinese cedar forest was remarkably higher than that of the moso bamboo forest.The habitats of L.juniperoideum were highly diversified in the Tianmu Mountain National Nature Reserve.The field investigation showed that the photosynthetic active radiation(PAR)ranges from 13.0 μmol·m2·s-1 to 44.0 μmol·m2·s-1,air humidity ranges from 67.8%to 98.2%and air temperature ranges from 18.9℃ to 31.1 ℃.Therefore,the typical habitats of L.juniperoideum were characterized by low cotent of soil N,P and K,acidic soil,shade and moist.2.In order to reveal the ecodaptation of L.juniperoideum,the experiments of the shade,the soil N,P,K and pH,the arid and high-temperature were made.The light test showed that this bryophyte maintained a highly photosynthetic rate in the PAR from 5 to 40 μmol m-2,and the largest photosynthetic rate occurred when PAR was on 80 μmol·m-2.A one-yeared shade test indicated that the bryophyte kept normal growth under the treatment of 75%shade,and be injured under the treatment of 50%or 95%shade on the conditions of routine potted cultivation.The arid and high-temperature test revealed that the plant was affected significantly by water deficit,and it reached the critical point(10.01%)at the condition with 38℃ and 50%relative humidity(RH)on the sixth day.Nitrogen,P and K fertilization experiments showed that L.juniperoideum was sensitive to the N additions of 0.05 mol·L-1,but not to the P and K additions.The pH test showed that seedlings of L.juniperoideum survived in the media of pH 4 and 5.5,but died out in the media of pH 6.5 and 8.0.The spore germination rates and the initial germinating time of L.juniperoideum were not affected by the pH stress,but the final germinating time was shorten as the pH rising.Therefore,the ideal culture conditions were the acidic soil with pH 4.0-4.5 and little soil N and moist,75%shading rate and RH 95%..3.For screening out the suitable propagating methods for L.juniperoideum,the methods of the small stem culturing and the tissue cculture were researched.The test of the small stem culturing showed that culture media were the key factors for moss farming,and the survival rate of L.juniperoideum seedlings was higher on the peat or the mixed media of peat and mountain clay(1:1)than the others.Tissue culturing test showed that the spore culture was very good.The sterilizing methods of capsules were disinfected with 75%alcohol for 5 s,then with 0.5%NaClO for 120 s.There are remarkable differences of the protonemata multiplication coefficients among the culture media,sugar and hormones.The multiplication coefficient of the protonemata cultred on the media of Beneck,l/2 MS,MS,1/4 MS,BCD and KM were separately 8.3,7.3,6.1,5.7,5.7 and 4.1 in turn.The maximum multiplication coefficient of the protonemata cultred on the media with sucrose and glucose were separately 19.2 and 22.9 at the concentration of 40 g·L-1.Except 10 μmol·L-1 GA3,there was no remarkable increase to the multiplication coefficient of the protonernata by adding 6-BA and IBA.Gametophytic bud spruted on the protonemata after being cultured in peat or agar media after one month.Among the factores affecting the gametophytic buds spruting,sugar was the most important.Fructose,glucose and sucrose all increased the gametophytic bud,and the suitable concentration was 15-20 g·L-1.The gametophytic bud initiation rate was remarkablely increased by KT,but no by ZT and 6-BA,and the suitable KT concentration for the gametophytic bud initiation was 0.5 mg·L-1.The value of medium pH also affected the gametophytic bud initiation rate and the suitable pH value was 4 to 5.5.Sugar and hormones helped to increase the reproduction rate of the gametophytic bud,and the effect of 2,4-D was higer than the others.Therefore,it was important to screen the suitable culture media for increasing the seedling survival rate,the protonemata multiplication coefficients,the gametophytic bud initiation rate and the reproduction rate of L.juniperoideum.4.For researching the rapid growing methods for L.juniperoideum,the experiments of the nutrient fertilization and the hormens additions wree made.The nutrient fertilization showed that there is a remarkable difference of the growth and physiological responses of L.juniperoideum among the treatments of nitrogen and phosphorus.Small ammonium nitrogen additions(4 gN·m-2)tended to increase its growth,while nitrate nitrogen additions decreased its growth.The phosphorus fertilization increased the growth of L.juniperoideum and the maximum yield occurred at 2 gP·m-2.The fertilization test of MS,Knop and Benecke showed that three kinds of solutions all increased the growth of L.juiperoideum and the maximum yield occurred at the concentration of 20-40 percent of the basic solution,but it may bring out counteraction over this concentration.Spraying hormone tests showed that hormones increased the growth of L.juniperoideum and the order of the growing rate by hormones were GA3,KT,6-BA,2,4-D and IBA in turn.Therefore,screening the suitable nutrients were critical to the rapid growing methods of L.juniperoideum,and the ammonium nitrogen,the phosphorus fertilization,the MS solutions,the Knop solutions and the Benecke solutions were all helped for the growing of L.juniperoideum.After the analysis,we considered that it was the discovering of the epigeic populations in the Tianmu Mountain National Nature Reserve that testified to the possibility of the introduction and cultivation of L.juniperoideum.But the soil N content and pH may be the limitation factors of the introduction and cultivation.The increasing the multiplication coefficient of the protonemata was the fast propagation methods for L.juniperoideum,and selecting appropriate culture media,sugar and hormones can increase the multiplication coefficient of the protonemata.The culture media,nutrients and hormones can increase the growth of L.juniperoideum seedling. |
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