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1.
Patterns of Assimilate Distribution and Source--sink Relationships in the Young Reproductive Tomato Plant (Lycopersicon esculentum Mill.) 总被引:1,自引:0,他引:1
Patterns of distribution of 14C were determined in 47-day-oldtomato plants (Lycopersicon esculentum Mill.) 24 h after theapplication of [14C]sucrose to individual source leaves fromleaves 110 (leaf 1 being the first leaf produced abovethe cotyledons). The first inflorescence of these plants wasbetween the buds visible and the firstanthesis stages of development. The predominant sink organs in these plants were the root system,the stem, the developing first inflorescence and the shoot apex(all tissues above node 10). The contribution made by individualsource leaves to the assimilate reaching these organs dependedupon the vertical position of the leaf on the main-stem axisand upon its position with respect to the phyllotactic arrangementof the leaves about this axis. The root system received assimilateprincipally from leaf 5 and higher leaves, and the stem apexfrom the four lowest leaves. The developing first inflorescencereceived assimilates mainly from leaves in the two orthostichiesadjacent to the radial position of the inflorescence on thevertical axis of the plant; these included leaves which weremajor contributors of 14C to the root system (leaves 6 and 8)and to the shoot apex (leaves 1 and 3). This pattern of distributionof assimilate may explain why root-restriction treatments andremoval of young leaves at the shoot apex can reduce the extentof flower bud abortion in the first inflorescence under conditionsof reduced photoassimilate availability. Lycopersicon esculentum Mill, tomato, assimilate distribution, source-sink relationships 相似文献
2.
Effect of Source of Nitrogen on the Growth of Fiskeby Soya Bean: the Carbon Economy of Whole Plants 总被引:1,自引:0,他引:1
Fiskeby V soya bean was grown from seed germination to seedmaturation with two contrasting patterns of nitrogen metabolism:either wholly dependent on dinitrogen fixation, or with an abundantsupply of nitrate nitrogen, but lacking root nodules. The carbonand nitrogen economies of the plants were assessed at frequentintervals by measurements of photosynthesis, shoot and rootrespiration, and organic and inorganic nitrogen contents. Plantsfixing atmospheric nitrogen assimilated only 2530 percent as much nitrogen as equivalent plants given nitrate nitrogen:c. 40 per cent of the nitrogen of nitrate plantswas assimilated after dinitrogen fixation had ceased in nodulatedplants. The rates of photosynthesis and respiration of the shootsof soya bean were not markedly affected by source of nitrogen;in contrast, the roots of nodulated plants respiredtwice as rapidly during intense dinitrogen fixation as thoseof nitrate plants. The magnitude of this respiratoryburden was calculated to increase the daily whole-plant respiratory loss of assimilate by 1015 per cent over thatof plants receiving abundant nitrate. It is concluded that nodulatedplants grew more slowly than nitrate plants inthese experiments for at least two reasons: firstly, the symbioticassociation fixed insufficient nitrogen for optimum growth and,secondly, the assimila tion of the nitrogen which was fixedin the root nodules was more energy-demanding in terms of assimilatethan that of plants which assimilated nitrogen by reducing nitratein their leaves. 相似文献
3.
Trifolium repens has two types of root, one derived from theseed and the adventitious roots derived from the stolon nodes.It has been suggested that these two systems have differentpotentials for supporting growth. This paper presents a comparisonof plants grown on single seedling or adventitious roots anddemonstrates that although the shoot: root ratios for the twotypes differ this may be explained by differing shoot morphologies.Comparison of the lamina: root ratios for the two types of plantproduced no statistically significant differences and it isproposed that the two types of root system do not differ intheir relationship with leaf growth. A mechanism for large diametertap root formation is suggested. white clover, Trifolium repens L., adventitious roots, seedling roots, shoot: root ratio 相似文献
4.
Root cultures of Lotus corniculatus L. cv. Leo transformed withAgrobacterium rhizogenes (C58Cl-pRi15834) grew rapidly in liquidmedium when cultured in the dark and produced large numbersof shoots when illuminated. The shoots, which could be regeneratedto produce fertile plants, were maintained in liquid mediumas shoot-organ cultures The accumulation and cellular distribution of condensed tanninswas determined during the growth of these root and shoot organcultures and in primary callus from non-transformed explants.Root and shoot cultures predominantly accumulated insolublepolymeric tannins which yielded both cyanidin and delphinidinon hydrolysis at ratios equivalent to control plants. Methanol-solublevanillin-positive compounds were isolated but no free oligomericproanthocyanidins, monomeric flavans or dihydroflavonols weredetected in these extracts. Condensed tannin accumulation waslinearly related to root growth and had a similar spatial distributionin tannin cells in roots and leaves as comparedto control plants. Tannin-containing cells were absent frommeristematic cells of the root tip and root/shoot interface.Primary callus cultures failed to accumulate condensed tanninson media containing auxins, and exogenously supplied auxinswere found to inhibit tannin accumulation by transformed rootand shoot cultures Key words: Lotus corniculatus, Agrobacterium rhizogenes, hairy roots, condensed tannins, shoot and root cultures. 相似文献
5.
Developmental control of xylem hydraulic resistances and vulnerability to embolism in Fraxinus excelsior L.: impacts on water relations 总被引:3,自引:0,他引:3
Welbaum G.E.; Bian D.; Hill D.R.; Grayson R.L.; Gunatilaka M.K. 《Journal of experimental botany》1997,48(3):655-663
The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 104M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar Alaska, an ABA-deficientmutant wil, and its wildtype. Freezinginjury was determined graphically as the temperature that caused50% injury (T50) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T50 for root tissuewas 1C for all genotypes, regardless of treatment. For Alaskashoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by 1.5 to 4.0C, while coldtreatment increased the freezing tolerance by 7.5 to14.8C. Cold treatment increased the freezing toleranceof shoot tips by 9 and 15C for wiland wild-type, respectively. Cold acclimationincreased endogenous ABA concentrations in Alaskashoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of Alaska, respectively.In Alaska shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in wiland wild-type shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization 相似文献
6.
Welbaum G.E.; Bian D.; Hill D.R.; Grayson R.L.; Gunatilaka M.K. 《Journal of experimental botany》1997,48(3):643-654
The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 104M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar Alaska, an ABA-deficientmutant wil, and its wildtype. Freezinginjury was determined graphically as the temperature that caused50% injury (T50) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T50 for root tissuewas 1C for all genotypes, regardless of treatment. For Alaskashoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by 1.5 to 4.0C, while coldtreatment increased the freezing tolerance by 7.5 to14.8C. Cold treatment increased the freezing toleranceof shoot tips by 9 and 15C for wiland wild-type, respectively. Cold acclimationincreased endogenous ABA concentrations in Alaskashoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of Alaska, respectively.In Alaska shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in wiland wild-type shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization 相似文献
7.
The time at which a bud began to expand was related to its positionnot only on an individual shoot but also within the crown. Thedistribution of buds and branches on the shoot was uneven; theshoot tip, where they were densely clustered, was termed thewhorl; and the remainder of the shoot, where they werewidely spaced, the interwhorl stem. In spring,the terminal bud started expanding before the whorlbuds which preceded the interwhorl stem buds;completion of the flush of growth, determined by the end ofleaf expansion, occurred in the reverse order, interwhorl> whorl > terminal. Similarly bud expansionstarted at the top of the crown and progressed downwards, andthe first shoots to complete their flush were at the bottomof the crown. Approximately 60% of the buds on each shoot beganexpanding in spring but only about half of these formed branches.Bud abscission began in May and by Sep. 45% of buds originallypresent had abscised. Most of-the buds that did not abscisewere the small buds at the base of the shoot that were not originallyassociated with a leaf. Approximately 42% of whorlbuds and 28% of MnterwhorP stem buds formed branches. Whorlbranches were approx. 60% longer that interwhorlstem branches; buds on the lower surface of the shoot producedlonger branches than those on the upper surface. The implicationsof the results for the development of crown form and selectionof superior oak are discussed. Quercus petraea, oak, buds, branches, crown form 相似文献
8.
Young plants of Banksia hookeriana were grown in acid-washedsand with adequate phosphate and water supply, and a proportionwere inoculated with Phytophthora cinnamomi. There were no majordifferences in growth between uninoculated and infected plants,but there was a large increase in uptake of 32P with increasingroot disease. In healthy plants 32P uptake was greatest in youngleaf tissue, but in diseased plants labelled phosphate was directedmore towards older leaves where the activity was almost twicethat of young leaves. Enhanced uptake with disease was ascribed to possible blockageof the message or signal of phosphatetranslocation from shoot to root, such that the diseased rootincorrectly treated the shoot as P deficient and increased Puptake. Key words: Banksia hookeriana, Proteaceae, 32P uptake, Phytophthora cinnamomi 相似文献
9.
Cytokinins in Xanthium strumarium L.: Distribution in the Plant and Production in the Root System 总被引:1,自引:0,他引:1
Cytokinins from leaf laminae, buds, petioles, stems, roots,and root exudate of mature vegetative plants of Xanthium strumariumL. were extracted, fractionated, and partially characterizedby means of column chromatography with Sephadex LH20. Two peaksof cytokinin activity with elution volumes corresponding tozeatin and zeatin riboside were detected, in varying concentrations,in all plant parts. A third cytokinin, detected only in petiolesand in expanding and mature leaves, eluted off the Sephadexcolumn before zeatin riboside. This cytokinin (peak a)was converted to zeatin or to a zeatin-like cytokinin followingboth acid hydrolysis and treatment with ß-glucosidase.Peak a was not detected in buds or in the youngestdeveloping leaves but was the predominant cytokinin presentin half-expanded and more mature leaves. By contrast, the zeatinriboside-like peak (peak b) constituted the majorcytokinin in root exudate, apical buds, and the youngest developingleaves, while not greatly contributing to the cytokinin contentof mature leaves. The detopped root system was shown to be capable of cytokininproduction. The distribution of cyrtokinins in the plant isdiscussed in relation to their probable origin in the root system. 相似文献
10.
The effects of three growth substances, viz. indol-3yl-aceticacid (IAA), gibberellic acid (GA3), and kinetin (KIN), and differentialshoot and root temperatures on growth of sugar-beet (Beta vulgarisL.) plants have been studied. IAA, GA3, and KIN were applied in aqueous lanolin at differentconcentrations (50 ppm to 5000 ppm) to decapitated sugar-beetplants at the eight-leaf stage, one group also having alternateleaves removed. The growth substances significantly increasedthe dry weights of the plants when all the leaves were present,which was mainly explained by the large increase in roots. Thegrowth substances probably stimulated cambial activity and hencethe mobilization of substrates resulting in a bigger root whena relatively large leaf area existed. The failure of the plantsto respond to treatments following the removal of alternateleaves suggests that under such conditions the growth substanceshave hardly any major effect on the production of substrates;rather they influence growth by regulating the movement of substratesby altering the sink strength if the supply ofsubstrates is not limiting. It could also be that the rootsproduce sufficient growth substances to maintain half the leavesat maximum expansion and maximum photosynthesis. Treatment withgrowth substances would therefore have little effect. When allthe leaves were present, they are limited by insufficient growthsubstances. All combinations of root and shoot temperatures of 17 and 25°C were imposed on plants decapitated at the eight-leafstage, one group also having each alternate leaf removed. Leaf8 expanded most at shoot and root temperature of 25 °C whereasother leaves had the largest areas at shoot and root temperatureof 17 °. When all the leaves were present root growth wasmaximal at shoot temperature of 17°C and root temperatureof 25 °C, but when alternate leaves were removed maximumroot growth occurred at shoot and root temperatures of 25 °C.Generally, a higher concentration of soluble carbohydrates wasfound in the roots and leaves when either the shoot or rootor both were kept at 17 °C. Concentrations of nitrogen,phosphorus, and potassium in different organs were less at 17°C than at higher shoot or root temperatures and decreasedwith age. 相似文献
11.
Characteristics of polarity are exhibited by a system in whichthe rate of synthesis of each of two diffusible morphogens withina plant body is inversely related to the concentration of theother by a suitable switching relationship. Simulations for a simple linear plant body show that, dependingon the value of a single parameter, the system can yield either(a) a stable state, with balanced concentrations of the twomorphogens, which is taken to represent an unpolarized condition,or (b) a state in which small local perturbations in concentrationresult in growing instability, representing initiation of polarity,and leading to a new stabilized distribution of concentrations,representing maintenance of polarity; there may arise eithertwo polarities (as for a plant with shoot and root) or one polarity(as for callus initiating either shoots or roots). Inductionof polarity in unpolarized tissue adjoining polarized tissueis also simulated. Properties of the system are discussed in relation to physiologicalprocesses, embryogenesis and hormone relations in normal plantsand in tissue culture. polarity, control system, morphogen 相似文献
12.
Nitrogen Utilization in N-limited Barley During Vegetative and Generative Growth: IV. TRANSLOCATION AND REMOBILIZATION OF NITROGEN 总被引:1,自引:0,他引:1
Barley (Hordeum vulgare L., cvs Golf and Laevigatum) was grownunder nitrogen limitation in solution culture until near maturity.Three different nitrogen addition regimes were used: in theHN culture, the relative rate of nitrate-N additionwas 0·08 d1 until day 48 and then stepwise decreasedto, finally, 0·005 d1 during late grain-filling;the LN culture received 45% of the nitrogen addedin HN; the CN culture was maintained at RA 0·0375d1 throughout growth. At four different growth stages(vegetative,anthesis, and twice during grain-filling), 15N-nitrate was fedto the plants. In some cases (split root cultures),label was fed only to one-half of the root system. These wereharvested directly after labelling, whereas standardcultured plants were harvested at termination of theexperiment (day 148). Absorption of added nitrate was nearlycomplete in the HN and LN cultures, and translocation of nitrogenwithin the plants could thus be studied independently of differencesin nitrate absorption. Cycling of nitrogen absorbed by vegetativeplants accounted for up to 50% of the nitrogen recovered inthe roots. The sink strength of the roots for cycling nitrogen,however, declined during post-anthesis growth, and net lossof nitrogen from both roots and vegetative shoot tissue occurredconcomitantly with incorporation of labelled 15N-nitrogen. Thenitrogen of the vegetative shoot tissue was substantially lesslabelled than the nitrogen entering the ears, indicating thattranslocation of recently absorbed nitrogen to ears occurs withminor prior exchange with the bulk nitrogen of shoots. In caseswhere the sink strength of the ears was weak, as in LN-culturedLaevigatum (due to high frequency of sterile flowers) and inCN-cultured Golf, nitrogen translocated from roots appearedto be incorporated into the vegetative shoot tissue. There werealso indications that a fraction of the remobilized nitrogenwas actually lost from the plants in these cases. It is concludedthat the root remains efficient in translocation of nitrogento the aerial parts throughout ontogeny and that nitrogen takenup during grainfilling is preferentially directly translocatedto the developing grains. The further translocation of nitrogenreceived by vegetative shoot parts to ears appears mainly relatedto the potential of the ear to accumulate nitrogen. Nitrogenabsorbed/remobilized in excess of the sink strength of the earsis either invested in continued shoot growth, or is irreversiblylost from the plants. Key words: Barley, 15N-labelling, post-anthesis, remobilization, translocation 相似文献
13.
Jeschke W. Dieter; Holobrad Margita; Hartung Wolfram 《Journal of experimental botany》1997,48(6):1229-1239
Maize (Zea mays L.) was grown in quartz sand culture eitherwith a normal root system (controls) or with seminal roots only(single-rooted). Development of adventitious rootswas prevented by using plants with an etiolated mesocotyl andthe stem base was positioned 58 cm above the sand. Eventhough the roots of the single-rooted plants were sufficientlysupplied with water and nutrients, the leaves experienced waterdeficits and showed decreased transpiration as trans plrationalwater flow was restricted by the constant number of xylem vesselspresent in the mesocotyl. As a consequence of this restriction,transpirational water flow velocities in the metaxylem vesselsreached mean values of 270 m h1 and phloem transportvelocities of 5.2 m h1. Despite limited xylem transportmineral nutrient concentrations in leaf tissues were not decreasedin single-rooted plants, but shoot and particularly stem developmentwas somewhat inhibited. Due to the lack of adventitious rootsthe shoot:root ratio was strongly increased in the single-rootedplants, but the seminal roots showed compensatory growth comparedto those in control plants. Consistent with decreased leaf conductance,ABA concentrations in leaves of single-rooted plants were elevatedup to 10-fold, but xylem sap ABA concentrations in these plantswere lower than in controls, in good agreement with the well-wateredconditions experienced by the seminal roots. Surprisingly, however,ABA concentrations in tissues of the seminal roots of the single-rooted plants were clearly increased compared to the controls,presumably due to increased ABA import via phloem from the water-stressedleaves. The results are discussed in relation to the role ofABA as a shoot to root signal. Key words: Zea mays, seminal roots, plant development, xylem transport, mineral nutrition, ABA, shoot-to-root signal 相似文献
14.
Diverse Responses of Maple Saplings to Forest Light Regimes 总被引:7,自引:1,他引:6
Seedlings of 11 species of forest maples (AcerL.) were grownoutdoors from budburst to senescence under three light regimes:gap centre under clear skies (approx. 20% opensky irradiance; red:far-red ratio=1.12); gap centre undercloudy skies (1.5%, ratio=1.03); and gap edge(2.5%, ratio=0.6). Seedlings grown under the gap centre (clearsky) regime had significantly greater height growth, greaterspecific leaf mass, higher root:shoot ratio, greater investmentin roots, higher leaf nitrogen concentrations, greater chlorophylla:bratio,lower photosynthetic rates under dim light, higher maximum photosyntheticrate, higher stomatal conductance, and lower leaf internal CO2concentrationscompared with those grown in either gap edge or gap centre (cloudy)regimes. Responses to the gap edgevs.gap centre (cloudy) treatmentsdiffer little, suggesting that shade acclimation in forest mapleseedlings is mainly a response to light intensity rather thanspectral quality. The ubiquitous and, except for leaf internalCO2concentration, highly significant interspecific variationin traits was broad-ranging and continuous. These results suggestthat (1) the responses to light quality found in shade intolerantherbaceous and woody species growing in more open habitats maynot have a selective advantage in seedlings of shade tolerantforest trees, and (2) the adaptive plastic response to understoreyvs.gapenvironments in forest maples, which is qualitatively consistentacross species, is founded on co-ordinated, small shifts insets of functionally inter-related traits.Copyright 1998 Annalsof Botany Company Acer,forest gap heterogeneity, plasticity, specific leaf mass, photosynthesis, leaf chlorophyll, nitrogen, stomatal density, root growth, root:shoot ratio, growth form. 相似文献
15.
In plants held under long days in the vegetative stage, youngexpanding leaves of poinsettia (Euphorbia pulcherrima Willd.Brilliant Diamond) are the main source of axillarybud inhibition, while the apical bud, which includes the meristem,primordial leaves and small unfolded leaves, is a secondaryinhibition source. Removal of these expanding leaves resultedin rapid release and growth of axillary buds. Decapitation ofthe apical bud resulted in delayed axillary bud release. Inreproductive plants kept in short days, the pigmented bractsare the primary source of axillary bud inhibition and the cyathiaare the secondary source. Applications of NAA substitutedfor both young leaves and bract inhibition maintainedapical dominance. The concentration of endogenous auxin washighest in the apical bud. However, when calculated on wholeorgan basis the auxin level was greater in young developingvegetative leaves and in reproductive bracts than in the apicalbud. Euphorbia pulcherrima Willd, apical bud, apical dominance, auxin, correlative inhibition, cyathia, poinsettia, IAA, NAA 相似文献
16.
The partition of 14C labelled current assimilates to root insimulated swards of Lolium perenne cv. S24 was measured duringthe transition from vegetative growth in autumn to reproductivegrowth in spring under close to natural conditions of lightand temperature. Assimilate partitioning was also measured inestablished swards cut three times during thegrowing season and in vegetative seedling swardsgrowing in autumn and in spring. All measurements were madewhen the swards had achieved more than 90 per cent light interception,and all swards were abundantly supplied with water and mineralnutrients. During autumn there was a gradual decrease in the proportionof assimilates partitioned to the roots in both the establishedand the seedling swards. In the established swards,partition to roots was low over winter, increased during earlyspring, but decreased dramatically, later in the spring, whenstem elongation began. In contrast, in the unvernalized vegatativeseedling swards in spring, partition to roots remained high. The seasonal pattern of assimilate partitioning is consideredin relation to changes in the natural environment and the rateat which the crop fixed carbon in photosynthesis. A decreasein the proportion of assimilates partitioned to roots duringlate spring was significant in increasing the production ofshoot at that time but seasonal differences in partition contributedvery little to the marked differences in shoot growth betweenthe spring and autumn crop. Lolium perenne L., perennial ryegrass, partition of assimilates, flowering 相似文献
17.
Decapitation and subsequent removal of unfolding leaves of sugar-beetplants (Beta vulgaris L.) at 2-, 4-, 14-, and 31-leaf stagesresulted in much greater growth of the remaining leaves, theeffect being more pronounced the less advanced the leaves atthe time of treatment. A two- to three-fold increase in areawas accompanied by a five- to six-fold increase in weight. Bothtreatments caused a transient increase in the rate of growthof the root, the promotive effect being sustained for a longerperiod at the later stages of growth when a greater photo-syntheticsurface was present than earlier. The results suggest that thesepromotive effects came mainly from the availability and distributionof substrates following the retardation of growth processesin the shoot and the removal of the shoot apex acting as a sinkof unknown size. Removal of part of the shoot resulted in proportionately greatergrowth of that remaining, whereas removal of part of the roothad no effect on the shoot unless it was reduced to one quarter.The change in the amount of shoot had no significant effecton the growth of the root, nor was there a compensating effecton the growth of the remaining root after more than one halfof it had been removed. Removal of more than one third of theroot resulted in an appreciable decrease in the net assimilationrate, while removal of part of the shoot of plants with thesame root sink strength led to an increased netassimilation rate. 相似文献
18.
Investigations revealed that the anatomy of the primary radicularroot of yam bean (Pachyrhizus erosus L.) was typically dicotyledonousexcept that the xylem was not completely developed centripetally.Most of the roots had tetrarch xylem, although a few triarchand pentarch roots were also observed. In both tuberous andnon-tuberous roots, secondary thickening occurred by the formationof the meristematic vascular cambium which formed secondarytissues in a normal fashion. Subsequently, tuberization wasinitiated in the secondary xylem by the development of anomaloussecondary cambia from parenchyma cells surroundingvessel elements. Anomalous secondary cambia alsodeveloped from parenchyma cells not associated with vessels.Subsequently, anomalous tertiary cambia differentiatedfrom tissues produced by the anomalous secondarycambia. Activities of these anomalous cambia resulted in theproduction of parenchyma storage cells and were chiefly responsiblefor the growth of the mature tuber. Pachyrhizus erosus L., yam bean, tuberous root, anatomy, anomalous secondary cambia, anomalous tertiary cambia, centripetal xylem development 相似文献
19.
Excised stem explants of Antirrhinum majus L. var. Kymosyblanc were grown in a denned medium to investigate factorsinfluencing bud and root development, callus induction, andsomatic embryogenesis. Auxins such as indoleacetic acid (IAA)and naphthaleneacetie acid (NAA) caused limited callus developmentand abundant root formation, whereas 2,4-dichlorophenoxyaceticacid (2,4-D) promoted soft friable callus with embryos and occasionaldevelopment of thick abnormal roots. 2-Naphthoxyacetic acid(NOA) and coconut milk (CM) used together induced friable greencallus growth and differentiation of small globular embryoswhich eventually developed into plantlets after transfer toauxin-free agar mineral medium containing sucrose. Cytokininssuch as benzyladenine (BA), zeatin, and kinetin induced compactgreen callus but in the absence of auxin failed to promote organogenesis.The interaction of IAA and kinetin resulted in the regenerationof the whole plant from stem explants. When NAA was used withkinetin, shoot development was totally inhibited and abundantroots were formed. Thus, the alternative morphogenetic eventsprobably reflect the biochemical subtleties occurring withinthe callus as a result of differences of actual endogenous levelsof growth substances in the tissues studied. These experimentshave been performed and interpreted on a histological basis. 相似文献
20.
KRIZEK DONALD T.; CARMI AVNER; MIRECKI ROMAN M.; SNYDER FREEMAN W.; BUNCE JAMES A. 《Journal of experimental botany》1985,36(1):25-38
Significant differences in response to soil moisture stress(SMS) and restricted root zone volume (RRZV) were found in twocultivars of soybean [Glycine max (L.) Merr.] (Forrestand Williams) plants grown under controlled-environmentconditions. Leaf water potentials of SMS-treated plants were0·4-0·6 MPa lower than those of controls and stomata1conductances 23-56% lower. In the case of RRZV treatment, however,there were no differences in either parameter. Initiation ofnew leaves as reflected in the plastochron index was stronglyreduced by SMS but was unaffected by RRZV. Photosynthetic rates(CO2 fixation dm2 of leaf) of plants given SMS were reducedby 11-21% while those of RRZV-treated plants were unaffected.SMS caused a strong preferential allocation of dry matter tothe root at the expense of the shoot in both cultivars. RRZV,however, had no effect on assimilate distribution in Forrestand only slightly favoured root growth in Williams.Carbohydrate concentrations of both alcohol-soluble and insolublefractions were increased significantly by SMS, especially inthe leaves, but were little affected by RRZV. Nitrogen concentrationin the root fraction was reduced by 22-24% and that in the leafand stem fractions by 7-14% under SMS but was not affected appreciablyby RRZV. Phosphorus concentration in the leaf, stem, and rootfractions was reduced by 45-65% under SMS but was relativelyunaffected by RRZV. These findings suggest that SMS and RRZVare basically different in their mechanism of action and thatthe impairment of growth resulting from these two stresses mayinvolve different physiological processes. Our results alsoindicate that the suppressive effects of small containers onplant growth do not necessarily result from inadvertent SMS. Key words: Drought, Container effects, Glycine max (L.) Merr 相似文献