Promoting function of seabuckthorn to increment of introduced foreign arbor trees in young growth period Yan Xiaoling

risk from the load, the information exchanges with complementation . A root system department structure especially changes into the biological cistern, Alleviating the drought stress the next adaptedness. Therefore, the seabuckthron is in the adverse circumstances, Because solving the fertilizer, water two that lack the life and the ecological factor ，but become the pioneer plant. The ecological function of the pioneers , Performance at to extensive adaptability of the adverse circumstances, diversity, plasticity, the stress resistance and easily live the quick growth etc.

nitrogen fixation；root system；bioreservoir ；Ecological factor；stress resistance

See from the standpoint of the ecology, the seabuckthorn as well as Actinorhizal plant ［1］,is also a clonal plant［2］. We so call it as that the pioneer tree species：Its ability is in the destructive environment, such as the marsh, sandy beach, discard the mineral falsely, the volcano explosion is behind place,the hungriness dune, drought ， half dry ，loess plateau etc［3］, Can be the first settle down the plant, growth, reproduction , combine for the companion plant and progeny plant of existence do a contribution.

The seabuckthorn with a nitrogen fixation of the symbiont , The nitrogen conduct and actions first crop-producing power and nourishments limit factor, carried out the life in the most important circulation: the C － N circulating organic link and operations, from the fixation nitrogen, provide nitrogen, the deadwood shed leaves familiar turn the soil, change to living environment comprehensive existence condition of the habitat ecotope.

The seabuckthron belongs to a clonal plant of root-suckering of root-derived.the root-suckering way carry on the asexuality breed, the genet and the ramet exist the resources share, risk spreaing , express a active type , persistent , across the spatiotemporal to expand, propagate ability strong and to bad the high endurance skill of the living environment.

This text tries to pass the organic contact and analysis,explain basic reason that the seabuckthron pioneer tree species,from the new angle of view understanding seabuckthron .

The main source of the combining nitrogen on the earth is a fixation nitrogen of biology . Fixaing nitrogen of symbiosis( a legume bacterium and Frankia strains ), account for 60% of fixation nitrogen total amount of bilogy . It is thus clear that, fixation nitrogen of symbiont, to nitrogenous source on the earth, the land ecological system nitrogen circulates to rise to emphasize to want the function with the ecological balance. The symbiont passes the fixation nitrogen of the Frankia strains, carrying out the plant photosynthetic carbon metabolism and conjunction of the nitrogen metabolism, starting the chemistry process of the life, lay the material and energy foundations for the growth and development of the plant. The seabuckthorn makes the soil nourishment with main reason of significant increment of amount of nitrogen, is pass fibros root continuously renewal, death, the putrefied of old nodules, life nodules Nourishment secrete, deciduous leal rot edc the result that synthesize.

Because the fixation nitrogen of the Frankia strain, solved the oneself to need 70-90% of the amount of nitrogen, therefore, don't depend on the soil to provide the nitrogen can exist ［5,6］. 9-10 red Alnus of ages, can provide the valid nitrogen plain 80-200 kg N2/ ha/ y toward soil annually, but together ages the Abies of the non-nodules, providing the 7-22 kg N2/ ha/ y only，the former is the latter 10 multiple［7 ］. The Casuarinaceae equisetifolia L of the Thailand tropical sand dune, can provide the total nitrogen to measure toward sandy soil 65-95% nitrogen ［8 ］. At have never growth the soil of Actinorhizal plant, inoculate the advantage Frankia strain, and transplant the seedling of the Alnus nodules,4 after month, the nitrogen content increased 78% of in the soil［9 ］. Another important function of the fixation nitrogen of symbiont, is to raised the plant to water keep and use coefficient ［10 ］.

At mixed forest ,7 ages seabuckthron，the average nodules of year measures for the 378 kg/ha/y,the average fixation nitrogen of year measures for the 54 kg N2/ha/y,equal to used the 119 kg/ha/y urea. The seabuckthron the year all sheds leaves to measure for the 2088 kg/ ha/ y, the leaf contains the amount of nitrogen(1.68-2.33%) far and high in mixed forest the Canada Poplar (0.57-1.43%) and the willow(0.75-1.50%) . And, a C/ N of leaf is low, be advantageous to quickly putrefied, increased the dissolubility nutrient. Therefore, mixed forest the organic mattter of soil , the whole nitrogen quantity of soil，and availability nitrogens high in the pure wood 37-42%,20.3-22.1% and 40-42%. At the same time, make the main wood leaf's productivity with amount of nitrogen increment 24%, the chlorophyll content increment 40%, tree high increment 18-19.4%, the breast diameter increment 27.1-28.9%, single plant volume measure increment 67.0-95.2%, raised the productivity of woodland unit area inside［11］

The experiment express that only put the symbiont of the Actinorhizal plant- Frankia , the ability contain strong ecological adaptability and the stress resistance. With the soil substrte electric potential for index sign of dry(-0.016 Mpas) and damp(-0.001 Mpas), and with inoculate( the advantage strains ) and don't inoculate( the native strains ), study the European Alnus seedling growth and nodulation with the fixation nitrogen ability. See of 4 month after, dry and damp don't affect nodulation of root system. But a nodules of the Alnus that inoculate inside, vesicle the integrity but vitalities high, don't inoculate of, the vesicle abnormal deformity and the quantity to reduce. Enunciation, only constitute the symbiont, the ability has the drought resistance ability, inoculating the advantage strains to the drought resistance is higher［12］. The poison that Actinorhizal plant to have the resistance aluminum harms the function, its reason is an aluminum and can combine with the Frankia strains surface protein, but reduced to the plant toxicity［13］. The symbiont has higher resistance to the cobalt of the surfeit.

Actinorhizal plant can reform to be farmland by the pollution of Nickel, its reason is an histidine of sour in the fixation nitrogen, can lower the poison of the Nickel to harm function［14］. The establishment of the symbiosis relation, also evocation to pathogen biggest resistence. The Casuarinaceae equisetifolia- Frankia symbiont, after salt( NaCl) stress (500 mgs/ L)6 weeks, young seedling still the ability normal growth and the nodulation, but the control young seedling that check against, after NaCl salt stress (300 mgs/ L),Caulis and fresh roots were heavy to all reduce obviously.The reason of the anti- salt, was a Frankia germ to strengthen the salt ability of reserve ［15］.

Actinorhizal plant, Frankia strains, all have diversity of the heredity and the ecological association. Use the RAPD method, grew the cluster to carry on to 12 seabuckthorn population allelic gene frequency discovers of autocorrelation after analytical, the non- sequence similarity amounts to 59.6% ［16 ］.The Framkia strains even has huge diversity. Exactly combine of diversity of both , just established to the existence the extensive adaptability and the stress resistance of the environment.

The host gene, come to a decision an occurrence of root nodules, formation and morphochoresis. But the physiology function of the host, then adapted the Frankia strains to host infection , the symbiotic system of regulate, protect the nitrogenase activity, provide the fixation nitrogen energy, the fixation nitrogen is behind transport with the nitrification thing, symbiosis environment of maintenance etc function. But the genotype of the Frankia strains, come to a decision to identify with particular host symbiosis, compatible, and the fixation nitrogen ability and vitalities of the symbiont. Exist the environment, provide the symbiont exertive to the environment adaptability, diversity, the stress resistance and the potential of the ecological functions. Therefore, Frankia strains with the perfect combination of the actinorhizal plant symbiosis, just showed to put huge ecosystem performance of theactinorhizal plant.

The seabuckthron is in the in the field it mainly the extension population by clonal root-suckering. But it also sexual reproductive phase. So, at seabkcuthron grove in the in the field, genet, ramet, clonal fragment,斑块 exist population diversity of heredities.

The seabucktron is a photophilous , the place of the root bucking It is all a full space of the light resources. Therefore, the seabuckthron foraging behavior, performance for have the selectivity to the resources. because root-suckering phyad, the resources differences and comprehensive function of the foraging behavior，the seabuckthron is in the ecosystem environment of distribute architecture, appeared to guerilla- type and phalanx- types. The former genet and ramet are more long-lost, the latter the plant and plant are more intensive, at two type exist to transition the type. This is the nature, basic reason of the seabuckthron various configuration.

The genet and ramet of the seabuckthorn, although their upper part is an independent individual, the underground department is mutually a conjunction . more important plant and of the plant ,exist the physiology function( material, information, hormone...etc.) up of mutually, call that the the physiological integration［17 ］. This kind of integration is subjected to the ramet duration of life , the ramet generation time, the duration of life of a physiology of plant conjunction decide. but at the resources unbalance, environment stress, the upper lyer vegetation to be overshadow, the remat forest land of resources to lack, the old plant senescence etc. is under circumstance, plant can take place the nourishment and water to transfer. This enunciation, a relation that exist" resources share", namely source -sink of regulate automatically. It is a adaptation of orientation that distributes to the resources plaque，

to the performance that environment stress ,thus raised under the adverse circumstances of existence ability. In time of the serious living environment stress , physiological integration is break, there will be the death of the remat. This phenomenon, also explain the physiological integration, the resources share, is conditioned. When to sacrifice the life, expressing another characteristics of" risk spreading " then, namely those weak plant dies of first.［18,19 ］

The clonal remet not only have the physiological integration, risk spreading, and, but also have the division of labour in the clonal. Connect of the ramet , can obtain the resources of the oneself want for from the other party availably, carry on exchange with complementation. Pass of reciprocal , mutualistic benefit of resources exchange, the material and informations collude with, further carrying out to stable orientation of the stress circumstances.

The symbiont function of the seabuckthron , the clonal configuration, the clonal behavior and habit, all have relation with root system. A root system of the seabuckthron , since is not a taprootsystem also is not fibrous root system , but the plane root but for main that superficial lamella root system . this is to be hereditary by it, a typing characteristic of a mutually consistent of ecological type. At the in the field, have the main root with the genet seedling of the seed germination formation, but decline mostly in laterly of grow up. With the ramet of root suckering formation, they only have the secondary root, but most for plane root shallow root( distribute in the soil deeply the 5-20 cm scope). The root thick in the 0.5-5 cm, can the elongation 10 cm , in laterly of grow, the plane root is more flourishing.

A root system of the seabuckthron can is divided into 4 parts to constitute:

1, the plane root, mainly is to by the bulky Ⅰ , the Ⅱ class seacondary root system constitute, its function is the physiological integration and saves the rain water and root suckering and symbiosises to nodulation ; 2, the plane root, a diameter is or so in the 1 mm,short for cluster gather ，the quantity is huge, renewing the very quick Ⅲ , and Ⅳ class fibrous root of seacondary; 3, growth at the Ⅰ , the Ⅱ class secondary root up of root suckering; 4, symbiosis at the Ⅰ , the Ⅱ class secondary root up of nodules.

Be showed from this, from the structure and functions up, seabuckthron root system hve a differentiation of obviously.

See from the ecological function, Ⅰ , the Ⅱ class 70-80% for secondary root, root layer distributes the shallow main reason, is in order to find out the light resources quickly, accept the rain water,and be advantageous to root suckering. The vascular cambium of seabuckthron secondary roots is belong to stratified cambium mode［20］, its characteristics is a cell to arrange tidy but fold the layer,the cell division direction run parallel with new cell wall and the organ surfaces,as a result increased the cell layer number,make adventitial cell organization thicken . So, adventitial cell layer of the seabuckthron root count much, can amount to 20-40 more layel. Grow from the different trees, such as seabucktrin and the black locust（Robinia pseudoacacia L）etc.,root of xylem area/ cross section area compare, the seabuckthron is 1/11.25, Babylon weeping willow （Salix babylonica）is 1/4.81, European white elm（Ulmus laevis） is 1/3.14, the Black Locust is 1/2.45; It is thus clear that, the root periderm of the seabuckthron is very flourishing, but the pipe is smaller and weak, its structure is dissimilarity from general ligneous plant , they took place to especially turn［21］.

Fig 1 periderm layer laminate cell of the seabuckthron root ×6000

Fig 2 periderm layer cytoplasm annular zone of theseabuckthron root ×6000

Author from transmission electron miroscope the slice to see deeply, adventitial layer cell of the root is a fold type ( figure 1,), the swelling after absorb water, laminate in after losing the water. The cell cytoplasm were squeeze by the central and big vacuolus the cytoplasmic annular zone, distributing between the central vacuolus and the cell wall( figure 2).

Fig 3 mitochondrial of periderm layer cytoplasm annular zone of theseabuckthron root ×30000

Fig 4 phagocytic vacuole and constitutive vacuole of cytoplasm of theseabuckthron root ×18000

The cell nucleus disappear, in the organelle cytoplasm, mitochondrial and vacuome to the lift only, is mitochondrial particularly in annular zone the quantity is most( figure 3). At the same time, still see the surroundings of the cell wall have phagocytic vacuole and constitutive vacuole（exocytosis）in great quantities.( figure 4). Enunciation, the periderm parenchymatous cell of the roots has the very high vitality. Its special structure and function, can generalize for: The central vacuolus is a place of aquiferous reservoir tissue,the mitochondrial of cytoplasm annular zone are the motive stations that the aquiferous reservoir release water tissue, the vacuolus ，phagocytic vacuole，and cytolemma receptor of annular zone ,to arrive the nutrient and water to absorb and information of release deliver the function. So inference, organization structure of these especially the the seabuckthron root system So inference, these especially organization structure of the seabuckthron root system ， use up of in the water , they rose to absorb water, reservoir water, regulate and obtund slowly release , have the physiological of the rhythmic water supply to an upper part of plant from automatic regulation control the system. The further research of author see, a saturation weight absorb water behind of the seabuckthron root system for dry weaght of 1.98 ploidy, but the collation Canada Poplar root that against only have 0.34 ploidy, the former is big in the latter 5.70 ploidy. This absorb water, reservoir water，obtund slowly release the function, guaranteeing the water supply of theroot buckering , and the need water of fixation nitrogen of root system ,Also raised at dry region, two rainfall, the seabuckthron to physiological supply that of transpiration loses water, Increased to the atmosphere,soil holdout ability of dry .

In fine, the seabuckthron conduct and actions actinorhizal plant fixation nitrogen of symbiosis, resolved to lack the fertilizer problem. Be the clonal plant, its physiological integration, raised to the adaptation ability of the stress tolerance.adventitial cell of root system especially changes into the biological cistern, alleviating the drought stress to the demanding antinomy of water. Therefore, in desert and stress, the seabucktion so performance for the excellent pioneer tree species basic reason , be it is a plant of dual ecological type , since solved to lack fertilizerfatty, also alleviated the water shortage of dual antinomy .

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