Effects of Wounding on Adventitious Bud Formation in Torenia Stem Segments Cultured In Vitro

In in vitro cultured stem segments of Torenia fournieri Lind.,the formation of adventitious buds can be induced when the culturemedium contains cytokinin. When long stem segments (2.0 cm ormore) were cultured with cytokinin, a large number of buds wereformed in the marginal regions, namely, within the limits of0.5 cm from the cut ends of explants, while only a few budswere initiated in the middle part of the explants. If a slightinjury was made transversely with a scalpel in the central partof an explant, a significant increase in the number of budswas noted within the limits of 0.5 cm from the wound site. Whena wounding treatment was given lengthwise to an explant, a largenumber of adventitious buds were formed over the entire surfaceof the explant compared to the control. Excision itself of explantsfrom mother plants and the additional wounding given to theexplants seemed to trigger the induction of adventitious buddifferentiation in Torenia stem segments. These wounding treatmentsdid not affect the uptake into explants and/or the distributionpattern of radioactive benzyladenine applied to the culturemedium. Key words: Torenia fournieri, Adventitious bud formation, Cytokinin, Wounding     

Adventitious Shoot Regeneration in Carnation (Dianthus caryophyllus) from Axillary Bud Explants

Adventitious shoots were regenerated from axillary bud explantsof 15 carnation cultivars. The use of leaf and stem explantswas not successful, largely due to explant senescence in thepresence of benzyladenine, kinetin and, to a lesser extent,zeatin. For axillary bud explants, a suitable optimum adventitiousregeneration medium contained Murashige and Skoog basal mediumsolidified with Gelrite and supplemented with 15 µm benzyladenineand 0.5 µM a-napthaleneacetic acid. Adventitious primordiaarose from the cut basal end of bud explants erupting as individualshoots after 2–3 weeks incubation. The axillary bud sizeand the time between subcultures of source material influencedthe production of adventitious shoots. Transfer of regeneratedshoots onto a medium solidified with agar minimized visiblesigns of vitrification. Regenerated shoots could be easily rooted,transferred to glasshouse conditions and grown to flowering. Vitrification, tissue culture, cut flowers, Dianthus caryophyllus L., carnation, cytokinins, explant     

Inhibition of Cytokinin-Induced Adventitious Bud Initiation in Torenia Stem Segments by Inhibitors of Serine Proteases

Application of di-isopropyl fluorophosphate (DFP), a highlysensitive inhibitor for serine enzymes, strongly inhibited cytokinin-inducedadventitious bud initiation in Torenia stem segments culturedin vitro. The inhibitory effect was not evident when DFP wasapplied after 3 days of culture. Amount of DFP-binding proteinsremarkably increased in superficial tissues of explants culturedfor 3 and 4 days on a medium containing benzyladenine. At least14 kinds of DFP-binding polypeptides were detected by SDS-polyacrylamidegel electrophoresis and fluorography. DFP-binding to some ofthese polypeptides was inhibited by a prior treatment with phenylmethylsulfonylfluoride and N-p-tosyl-L-lysine chloromethyl ketone. From theseresults, it was suggested that some serine proteases might berelated with biochemical events occurring during the initialstage of adventitious bud differentiation in Torenia stem segments. (Received May 8, 1984; Accepted July 5, 1984)     

Shoot Formation from Explant Cultures of Fourteen Potato Cultivars and Studies of the Cytology and Morphology of Regenerated Plants

Plants were regenerated in quantity from cultured excised stem,rachis or leaf pieces of 13 potato (Solarium tuberosum L.) cultivarsusing modifications of a two-step procedure. Pronounced differenceswere observed in the response of different cultivars and explantsources to medium formulations containing different auxins orcytokinins. A few plants were recovered from tuber pieces ofseven cultivars by a different two-step procedure. Morphologicaldifferences from control plants were observed in some of theprimary regenerants. Anthocyanin pigmentation of tubers wasscored and stable changes to red-splashed white or white tuberswere found in some plants regenerated from cv. Desiree. Regenerantsfrom the particoloured cultivars Cara and King Edward oftenlost this trait but it returned to varying extents in subsequentgenerations. Most of the regenerated plants (87 per cent) containedthe euploid number of chromosomes (2n = 4x = 48). The methodsare suitable for production of plants for assessment of somaclonalvariation in a range of genotypes. Potato breeding, somaclonal variation, chromosome variation, skin colour, explant culture, plant regeneration, solanum tuberosum L. potato     

Uptake and Partitioning of Nitrogen by Maize Infected withStriga hermonthica

The uptake and partitioning of nitrogen (N) by maize infectedwith the parasitic angiosperm,Striga hermonthicawas investigatedin sand culture in a glasshouse. The purpose was to determinethe effect ofStrigaon N uptake and partitioning in maize. Maizewas grown at 22, 66 and 133 mg N per plant and sampled fivetimes. There was no significantStrigaxN interaction in any measuredresponse. Leaf dry matter ofStriga-infected maize, averagedover all N treatments, was 92% that of uninfected maize at thefour-leaf stage but by the 18-leaf stage it had decreased to58%. Similarly, stem dry matter of infected maize which was91% that of uninfected maize at the four-leaf stage was only42% at the 18-leaf stage. Root dry matter was similar for infectedand uninfected maize. N concentration in the leaf, stem androot declined asymptotically from the first to the last samplingdate for both infected and uninfected maize. The asymptoticvalue of N concentration inStriga-infected maize was 16% greaterin the leaf, 55% in the stem, and 21% in the root than in uninfectedmaize. The concentration of N inStrigawas higher than in maizeat the 16- and 18-leaf stages. Uptake of N was similar for infectedand uninfected plants at the four–eight leaf stage butat the eight–12 leaf stage, N uptake by infected maizewas 52% that of uninfected maize. However, the proportion oftotal plant nitrogen partitioned to the root was greater (P<0.001)forStriga-infected maize. These results showed that the extentto whichS. hermonthicareduced maize growth and N uptake, butincreased the proportion of N partitioned to the roots, didnot depend on the rate of N fertilizer applied.Copyright 1998Annals of Botany Company Maize; nitrogen; partitioning;Striga hermonthica; uptake.     

Clonal Fidelity and Variation in Plantain (Musa AAB) Regenerated from Vegetative Stem and Floral Axis Tips in vitro

Recognition of a phenotypically distinct 'French-type' plantain(Musa AAB) designated 'Superplatano' (Superplantain) promptedevaluation of in vitro micropropagation as a means of generatingsufficient numbers of plants for field evaluation in three locationsin Puerto Rico. A multi-faceted study designed to evaluate relationshipsbetween different aseptic culture procedures and morphologicalorigins of primary explants was carried out. Vegetative budsfrom various positions relative to the mother corm (definedby cardinal points on the compass) and explants from the floralaxis of 'Maricongo' (the 'False-Horn', or florally determinatetype 'progenitor' of 'Superplatano'), and 'Superplatano' (a'French-type') were used as starting materials. Responses underfield conditions were studied using a number of parameters includingyield of commercially marketable fruits. We compared four populationsof shoots, each of which derived from at least three differentshoots from within one mat, shoots derived from vegetative andfloral material from the same mat for both 'Maricongo' and 'Superplatano',and shoots derived from a number of floral buds of the sameclone ('Maricongo') all of which were in culture for the samelength of time. 'Superplatano' was stable whether from vegetativecorm or floral bud apex. This shows conclusively that if thestarting point in the micropropagation process is a stable Musaclone, our tissue culture procedure is reliable. Considerablevariation in bunch phenotype was observed, however, in plantsregenerated from ten of 12 shoot and floral meristems startedfrom the 'False-Horn'-type 'Maricongo'. Change from 'False-Horn'-type(determinate) to 'French'-phenotype (indeterminate) was evidentin each of the three locations. Frequency of bunch reversionvaried from 0·4 to 100%, but was confined to individualoriginating stem tips rather than clones. The most dramaticbunch phenotypic change occurred in plants regenerated fromclone 3. All plants regenerated from shoot 3-North bore 100%'French-type' bunches. However, reversion in plants regeneratedfrom shoot 3-West was only 1·8%, and no bunch phenotypicchange was observed in plants from shoot 3-East. Plants regeneratedfrom both shoot and male floral axis tips in 'Maricongo' clone4 also bore 'French-type' bunches. Frequency of bunch reversionfrom shoot 4-East was 0·4% as compared to 2·6%from 4-floral. Bunch reversion occurred at the frequency of2·0% when plants were regenerated from clone 6-floral.No bunch reversion was observed in plants regenerated from asingle shoot tip in clones 1-West and 5-floral. No dwarfismwas encountered in any of the tissue culture-derived plants.We conclude that tissue culture per se plays a very small role,if any, in the direct induction of off-types. Pre-existing characteristicsof the primary explant determines whether products of a multiplicationshow fidelity or not. Our data suggest that 'Maricongo' is achimera and that 'Superplatano' is revertant off-type that resultswhen breakdown of the chimera occurs. Large numbers of stable'Superplatano' were produced from unstable 'Maricongo' and thisaffirms the value of micropropagation for generation of cloneswith desirable bunch phenotype.Copyright 1993, 1999 AcademicPress Musa, plantains, bananas, tissue culture, clonal multiplication, somaclonal variation, phenotype     

Correlative Inhibition of Lateral Bud Growth in Phaseolus vulgaris L.--Influence of the Environment

The influence of various environmental factors upon main stemand lateral bud growth has beeninvestigated using Phaseolusvulgaris, with the object of discovering why there is variabilityin the response of lateral buds on decapitated plants to apically-appliedIAA. Light intensity, light quality and temperature had differentand specific effects on main stem and lateral bud growth inintact plants and on the effectiveness of IAA in inhibitingprimary leaf axillary bud growth in decapitated plants. Photoperiod,on the other hand, was apparently ineffective. It is concluded that environmental factors, as well as contributingto the normal regulation of apical dominance, could also partlyor wholly account for the variation in effectiveness of appliedIAA found by different workers. IAA was least effective whenthe temperature was lower at night than during the day.     

Distribution of {beta}-Thioglucosidase Activity in Intact Plants, Cell and Tissue 6Brassica napus L.

Distribution of myrosinase activity in extracts from seeds,intact plants, cell cultures and regenerated callus and plantsof Brassica napus L. was determined by the rate of glucose formationfrom glucosinolate hydrolysis. Calli with shoots and regeneratedplants were obtained from protoplasts or from explants. Of the seedling organs from Brassica napus L. cv. Niklas, hypocotylsshowed the highest myrosinase activity. In cotyledons a nearlyconstant enzyme activity was determined over the first 6 d,followed by a gradual decline. Roots showed a fast decline inenzyme activity over the investigated period. Freshly-isolated protoplasts contained less myrosinase activitythan the original intact tissue. The enzyme activity in developingcalli generally decreased during the first culture periods.After the initial decline a low activity was found which wasstable for a period of more than 2 years. The enzyme activityshowed fluctuations when measured at different times after mediumchange. Protoplast calli with regenerated shoots showed a considerablyhigher myrosinase activity than calli without shoots. Myrosinaseactivity was also found in explant calli including explant callifrom cotyledons and hypocotyls after induction of shoots. Myrosinase activity in seeds from 21 cultivars of Brassica napus,Brassica campestris, Sinapis alba and Raphanus sativus was testedand the highest myrosinase activity was found in seeds fromthe Sinapis alba cultivar Trico while the lowest activity wasfound in the Brassica campestris cultivar Rapido III. Leaf, stem and inflorescence from flowering regenerated or seed-grownplants contained a low but significant myrosinase activity.In contrast, roots showed a high myrosinase activity. The resultsobtained from regenerated plants indicate that the myrosinasesystem is stable in vitro culture, and that the glucosinolate-myrosinasesystem is active in calli tissue. Key words: Myrosinase (thioglucoside glucohydrolase, E.C. 3.2.3.1), in vitro cultures, intact plants     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

The Responses of Field-grown Sunflower and Maize to Mechanical Support

The effects of mechanical support on two contrasting speciesof herbaceous annual, the dicot sunflower (Helianthus annuusL.) and the monocot maize (Zea mays L.), were investigated bycomparing the growth and mechanical properties of supportedplants and those which were left to sway freely in the wind. Providing support had its greatest effect on the more highly-stressedbasal areas of the plants, such as the lower stem and the baseof the lateral roots. The diameter of the stem bases of bothspecies was approx. 10% lower in supported plants, but therewas no difference between treatments in the diameter of thestem above 50 cm. Roots of both species also showed a reductionin rigidity and bending strength of 40–50% in the supportedplants compared with freely swaying plants. There was a significantreduction in the partitioning of biomass to the root systemsof supported plants of both species. There were differences in the way in which sunflower and maizeresponded to the provision of support; in sunflower, the reductionin lateral diameter was about twice that in maize, whereas inmaize the decrease in the number of first-order laterals wastwice that of sunflower. This study suggests that thigmomorphogenesismay be a localized response, but that different species canrespond in different ways to mechanical stimulation. Wind; support; anchorage; thigmomorphogenesis; Helianthus annuus L.; sunflower; Zea mays L.; maize     

Factors Controlling the Basipetal Pattern of Tuberization in Induced Potato (Solanum tuberosum L.) Cuttings

Potato plants (Solanum tuberosum L. cvs Chippewa and Katahdin)were grown in a glasshouse under continuous light. Various numbersof long (16 h) nights were given to these plants and stem cuttingswere taken. Treatments were applied to the cuttings, which werethen placed in a mist bench under continuous light and examinedfor tuberization after 12 days. The general tendency for the strongest tuberization to occurat the most basipetal nodes, which is commonly seen with intactpotato plants, was also found on stem cuttings. This patterncould not be attributed primarily to orientation with respectto gravity, proximity to the mother tuber, or age of buriedbuds. Buried buds farthest from active leaves tended to tuberizethe most strongly. However, distance of the buried bud fromstem exposed to light may have been of equal or greater importance. potato, Solanum tuberosum L., stem cuttings, tuberization     

Hormonal Control of Morphogenesis in Leaf Explants of Perilla frutescens Britton var. crispa Decaisne f. viridi-crispa Makino

Leaf discs of Perilla frutescens var. crispa f. viridi-crispawere cultured on a defined medium to investigate factors influencingbud and root formation, callus induction, somatic embryogenesis,and floral bud formation. Addition of naphthalene-acetic acid(NAA) to the culture medium caused compact callus whereas 2,4-dichlorophenoxyacetic acid (2,4-D) promoted soft and friable callus formationon the surface of the explants. Benzyladenine, when appliedwith auxin, suppressed callus and root formation. Somatic embryogenesisoccurred, when the explants were first grown on nutrient mediumcontaining 2,4-D and organic elements, and then transferredto the 2,4-D free medium. Treatments with cytokinins, N-phenyl-N'-(4-pyridyl)urea and its derivatives induced bud formation. A low concentrationof NAA and naphthoxy-acetic acid promoted bud development. Occasionalfloral bud formation was observed depending on the originalleaf positions on mother plants from which the leaf discs wereexcised. A gradient of floral bud forming capacity along thestem was noted. Perilla frutescens, tissue culture, embryogenesis, morphogenesis, benzyl adenine, kinetin, naphthalene-acetic acid, naphthoxy-acetic acid, 2,4-dichlorophenoxy acetic acid, indol-3yl-acetic acid, cytokinins, auxins     

Regulation of Branching in Decussate Species with Unequal Lateral Buds

In the decussate plants Alternanthera philoxeroides and Hygrophilasp. the opposite axillary bud primordia are of unequal sizefrom the time of their inception; the larger or + buds lie alongone helix and the smaller or – buds along another (helicoidalsystem). In decapitated plants of Alternanthera both buds grewout, but unequally; if the node was vertically split growthof the two shoots was more equal, and if the + buds were excisedgrowth of the – shoots approximately equalled that ofcontrol + shoots. In decapitated shoots of Hygrophila grownin sterile culture only one bud, the + or larger one, grew outat each of the upper nodes. In excised cultured nodes, also,only the + bud grew out; but if the nodes were split longitudinallyboth buds grew out, initially rather unequally. These experimentssupport the view that the regulation of branching in these specieshas two components, apical dominance and the dominance of thelarger (+) bud over the smaller (–) bud at the same node.The restriction of growth potentiality imposed on the –bud is not permanent but can be modified. Further correlativeeffects on bud outgrowth include those of the subtending leavesand of buds at other nodes.     

The Interaction of Genotype, Explant and Media on the Regeneration of Shoots from Complex Explants of Brassica napus L.

The relative importance of explant type, genotype and growthregulator regime in the determination of shoot regenerationfrequencies from complex explants of Brassica napus L. has beenevaluated. Cotyledon, hypocotyl and stem sections taken fromone spring (Westar) and three winter (Ariana, Cobra, Libravo)varieties of B. napus were cultured on three different growthregulator regimes, 0.5 mg dm^–3 NAA + 2.0mg dm^–3BAP, 0.5 mg dm^–3 NAA + 4.0mg dm^–3 BAP and 1.0mgdm^–3 NAA + 4.0mg dm^–3 BAP. The most significanteffects on shoot regeneration were due to explant type and variety.The regeneration from stem segments was not only two to threetimes higher than from hypocotyls or cotyledons, in all varieties,but the response was also more uniform across the varieties.The explant effect accounted for 44–95% of the regenerationresponse. In contrast, the contribution of growth regulatorregime was negligible. Although the growth regulator regimeas an independent effect was unimportant, regeneration fromboth Ariana and Libravo was significantly affected by the interactionof genotype with growth regulator regime. The importance ofboth the high shoot regeneration frequency from stem segmentsand the relative uniformity of response across the four testedgenotypes is discussed with respect to the potential benefitsof using this explant source in Agrobacterium-based transformationexperiments. Key words: Brassica napus, regeneration, genotype, tissue culture, complex explant     

Lateral Bud Growth in Phaseolus vulgaris L. and the Levels of Ethylene in the Bud and Adjacent Tissue

Ethephon and the ethylene inhibitors Ag⁺ and aminoethoxyvinylglycine (AVG) inhibited outgrowth of the axillary bud of thefirst trifoliate leaf in decapitated plants of Phaseolus vulgaris.Endogenous ethylene levels decreased in the stem upon decapitationalthough it is not conclusive that a causal relationship existsbetween this decrease and the release of axillary buds frominhibition. The proposition that auxin-induced ethylene is responsiblefor the suppression of axillary bud growth in the decapitatedplant when the apical shoot is replaced by auxin is not borneout in this study. Application of IAA directly to the axillarybud of intact plants gave rise to a transient increase in budgrowth. This growth increment was annulled when AVG was suppliedwith IAA to the bud despite the fact that the dosage of AVGused did not affect the normal slow growth rate of the bud ofthe intact plant or bud outgrowth resulting from shoot decapitation.     

花生体细胞的器官发生和植株再生

以已萌发的花生种子不同部位为材料,比较了完整的胚芽、主芽,侧芽,胚轴及子叶等培养力的差异,得出了如下结果: 1.在外植体培养过程中,花生的胚轴具有强烈的再生能力;其它部位培养力大小的顺序依次是:完整的胚芽>主芽>侧芽>子叶>叶片。2.通过试验证明,花生外植体培养的最佳激素组合是NAA 0.6毫克/升+BA 0.9毫克/升。     

Artemisinin production by shoot regeneration of Artemisia annua L. using thidiazuron

An efficient in vitro method for multiple shoot bud induction and regeneration has been developed in Artemisia annua L. using leaf and stem explants in various concentrations and combinations of plant growth regulators to evaluate the frequency of regeneration. The sources of explants as well as plant growth regulators in the medium were found to influence the multiple shoot induction. The result shows that the stem segment cultured on Murashige and Skoog (MS) medium supplemented with 0.1 mg/l thidiazuron (TDZ) gave a perfect shoot formation (100%) and good shoot multiplication (57 shoots/explant) after 2 weeks of culture. Healthy regenerated shoots were elongated and rooted in MS medium without hormones. The artemisinin content in plants regenerated from stem explants using 0.1 mg/l TDZ was (3.36 +/- 0.36) microg/mg dry weight and two-fold higher than that of in vitro grown plants of the same age [(1.73 -/+ 0.23) microg/mg DW]. This system exhibited a potential for a rapid propagation of shoots from the stem explant and makes it possible to develop a clonal propagation of A. annua.     

多肉植物离体再生研究进展

通过品种、外植体类型、培养基、外源植物激素的选择等几方面对国内多肉植物的离体再生研究现状进行了综述。发现多肉植物的离体再生研究多以种子、叶片、茎段、花器官等为外植体;不定芽诱导阶段常用的培养基类型为MS培养基,不定根诱导常用1/2 MS培养基;6-苄氨基腺嘌呤(6-BA)、萘乙酸(NAA)和激动素(KT)作为常见的外源植物激素,被广泛运用于多肉植物愈伤组织诱导、不定芽诱导、不定根诱导等离体再生各阶段;分析了当前存在的问题和发展前景,以期为日后多肉植物的相关研究提供可行性建议。     

Topophysis affects the Potential of Axillary Bud Growth, Fresh Biomass Accumulation and Specific Fresh Weight in Single-stem Roses (Rosa hybrida L.)

Topophysis, the effect on growth and differentiation of positionof axillary buds along the shoot, was studied by propagatingfive-leaflet-leaf single-node cuttings which were excised fromseven stem positions and grown as single stemmed plants. InRosahybrida ‘Korokis’ Kiss®, ‘Tanettahn’Manhattan Blue®, and ‘Sweet Promise’ Sonia®,following release of the buds from apical dominance by excision,morphogenetic development was studied until anthesis. The timefrom excision/planting until onset of bud growth, visible flowerbud appearance, and anthesis was generally shorter in plantsoriginating from apical bud positions than from basipetal positions.Topophysis mainly affected the onset of axillary bud growth;the earliest growth and development was found in cuttings fromthe second uppermost node position. This node tended to havethe lowest plastochron value, which indicated the existenceof a transition between sylleptic and proleptic buds. Stem lengthat visible flower bud and at anthesis generally increased asthe cutting position changed basipetally until the second lowestposition, and the number of five-leaflet-leaves at anthesisand the total number of nodes generally increased basipetally.For internode length, growth rate, and fresh biomass efficiencythe cuttings taken from the uppermost and lowermost positionsgenerally had significantly lower values than cuttings fromall medial positions. At anthesis, plants originating from cuttingsexcised from lower medial positions generally had a higher freshweight, greater flower stem diameter, and a significantly higherspecific fresh weight than those plants originating from apicalor basal positions. Among the cultivars, Sonia was the mostefficient in increasing fresh biomass and had the highest growthrate, whereas Manhattan Blue possessed the highest specificfresh weight, indicating a higher plant quality. It is suggestedthat topophysis inRosa is an independent phenomenon intrinsicto the axillary bud. apical dominance; axillary bud growth; fresh biomass accumulation; cut rose; flowering; Rosaceae; Rosa hybrida L.; rose; shoot growth; single-stem roses; specific fresh weight; topophysis; quality     

香艳梨离体培养研究

本试验以香艳梨的茎尖,不带芽茎段,带芽茎段,叶片,叶柄为试材,以１／２ＭＳ为基本培养基,分别附加０．５～２．０ｍｇ／Ｌ的６－卡基氨基嘌呤（６－ＢＡ）和０．１ｍｇ／Ｌ的萘乙酸（ＮＡＡ）、吲哚乙酸（ＩＡＡ）,２,４－二氯苯氧乙酸（２,４－Ｄ）进行离体培养研究。结果表明,试材用０．１％ＨｇＣｌ２灭菌５～６分钟为宜;在７月份接种感染率低,愈伤组织形成较快;茎尖,不带芽茎段,带芽茎段,叶片均可作为离体培养的外植体,叶片的脱分化,分化的效果尤为明显,叶柄不宜作外植体;１／２ＭＳ＋１．５ｍｇ·Ｌ－１６－ＢＡ＋０．１ｍｇ·Ｌ－１ＮＡＡ有利于脱分化;１／２ＭＳ＋１．０ｍｇ·Ｌ－１６－ＢＡ有利于分化;瓶外生根优于瓶内生根。本试验可为香艳梨的工厂化育苗提供参考。