Penetration and colonization of resistant and susceptible Apium graveolens by Fusarium oxysporum f.sp. apii race 2: callose as a structural response

1988 ◽  
Vol 66 (12) ◽  
pp. 2385-2391 ◽  
Author(s):  
C. M. Jordan ◽  
R. M. Endo ◽  
L. S. Jordan
Keyword(s):  
Fusarium Oxysporum ◽  
Host Cell ◽  
Cell Walls ◽  
Vascular Tissue ◽  
Periodic Acid ◽  
Light And Electron Microscopy ◽  
Structural Response ◽  
Aniline Blue ◽  
Apium Graveolens ◽  
Race 2

Root apices of Apium graveolens L. resistant and susceptible to race 2 of Fusarium oxysporum f.sp. apii (R. Nels. & Sherb.) were studied at various times after inoculation, using light and electron microscopy to determine structural response(s) of the hosts during penetration and colonization by the pathogen. Penetration was intercellular and intracellular and involved mechanical and enzymatic mechanisms. At the onset of penetration, the host cell walls manifested fluorescence, induced with either aniline blue or sirofluor, at the point of penetration. The fluorescent area was more intense and larger in the resistant host. Fluorescence disappeared with time. After incubation with β-1,3 glucanase fluorescence disappeared, indicating β-1,3 polysaccharide (probably callose) presence. Callose deposits were 2 and 3 times greater in the epidermis and 4 and 9 times greater in the cortex of the resistant than in two susceptible hosts, respectively. Hyphal counts in the cortex of the resistant host were 50% fewer than in the susceptible hosts. Increased callose deposition on host cell walls was associated with reduced colonization. Callose formed in vascular tissue as the fungus colonized it. Callose detection with sirofluor was more sensitive; background fluorescence common with aniline blue without periodic acid – Schiff's reagent pretreatment was absent.

Ultrastructure of compatible and incompatible interactions of soybean roots infected with the plant pathogenic oomycete Phytophthora sojae

1997 ◽  
Vol 75 (9) ◽  
pp. 1493-1508 ◽  
Author(s):  
K. Enkerli ◽  
C. W. Mims ◽  
M. G. Hahn
Keyword(s):  
Host Cell ◽  
Vascular Tissue ◽  
Light And Electron Microscopy ◽  
Phytophthora Sojae ◽  
Host Responses ◽  
Plant Responses ◽  
Cortical Cells ◽  
Wall Appositions ◽  
Race 2 ◽  
Incompatible Interactions

Compatible and incompatible interactions of two soybean isolines containing either Rps1a or Rps1b resistance genes with races 2 and 8 of Phytophthora sojae were examined by light and electron microscopy. Phytophthora sojae race 2 is virulent on Rps1b plants and avirulent on Rps1a plants. Race 8 shows the reverse reaction; it is avirulent on Rps1b plants, but virulent on Rps1a plants. All combinations of races and cultivars were examined at times ranging from 30 min to 20 h postinoculation. Zoospore encystment, germination, and infection occurred within 30 min in all interactions. No evidence of appressorium formation was found. Wall appositions in epidermal cells adjacent to hyphae were very frequent by 30 min postinoculation. Differences between compatible and incompatible interactions became evident as early as 4 h postinoculation. The major difference appeared to relate to timing of host responses, which lead to two different types of relationships. In compatible interactions, P. sojae exhibited a short biotrophic phase with the establishment of many haustoria without triggering visible plant responses in cortical cells until approximately 10 h postinoculation. By 15 h postinoculation, almost the entire root was necrotic, wall appositions were abundant, and vascular tissue was colonized. The incompatible interaction was characterized by a nearly complete absence of haustoria, rapid host cell necrosis, and formation of many wall appositions by 4 h postinoculation. The pathogen rarely penetrated beyond the endodermis of the resistant host and colonization of vascular tissue was rare. Overall there were clear ultrastructural differences between compatible and incompatible interactions of soybean with P. sojae. These data support a strong correlation of resistance with host cell death, formation of wall appositions, and absence of root stele colonization. Key words: Phytophthora sojae, Glycine max, host–pathogen interaction, ultrastructure.

Association of phenol-containing structures with Apium graveolens resistance to Fusarium oxysporum f.sp. apii race 2

1989 ◽  
Vol 67 (11) ◽  
pp. 3153-3163 ◽  
Author(s):  
C. M. Jordan ◽  
L. S. Jordan ◽  
R. M. Endo
Keyword(s):  
Fusarium Oxysporum ◽  
Vascular System ◽  
Light And Electron Microscopy ◽  
Apium Graveolens ◽  
Cell Periphery ◽  
Xylem Parenchyma ◽  
Parenchyma Cells ◽  
Entire Plant ◽  
Phenolic Substances ◽  
Race 2

Electron-opaque (EO) structures were studied, using light and electron microscopy, in the xylem parenchyma cells and vessels of both incompatible and compatible Apium graveolens L. var. rapaceum (celeriac) and compatible Apium graveolens L. var. dulce (celery) roots 24 h after inoculation with Fusarium oxysporum f.sp. apii race 2. Few small EO bodies were observed in the noninoculated hosts. Histological, cytochemical, and chemical tests indicated the presence of phenolic substances and polysaccharides in the EO materials. These EO structures increased both in number and size as infection progressed. The incompatible host produced three and five times more of the EO materials than the compatible celeriac and celery, respectively. The amount of the EO materials and host compatibility were related to the absence and presence of fungal hyphae in the vascular system. Hyphae either associated with or enveloped by the EO structures were vacuolated; their cytoplasm was restricted to the cell periphery. Occlusion of the xylem vessel pores of the incompatible host with the EO structures likely prevented upward spread of the pathogen throughout the entire plant.

Peculiar ultrastructural characteristics of fungal cells and of other elements apposed to and in vessel walls in plants of a susceptible carnation cultivar, infected with Fusarium oxysporum f.sp. dianthi race 2

2005 ◽  
Vol 85 (3) ◽  
pp. 121-138 ◽  
Author(s):  
Guillemond B. Ouellette ◽  
Robert P. Baayen ◽  
Danny Rioux ◽  
Marie Simard
Keyword(s):  
Fusarium Oxysporum ◽  
Host Cell ◽  
Outer Layer ◽  
Cell Walls ◽  
Vessel Elements ◽  
Tissue Degradation ◽  
Ultrastructural Characteristics ◽  
Vessel Walls ◽  
Race 2

Abstract Ultrastructural characteristics and cytochemical reactions of unusual, irregular elements (IE) in vessel elements in susceptible carnation plants infected with Fusarium oxysporum are reported. As revealed by labelling for chitin, fungal cells in contact with host cell walls or content had altered or defective lucent layers, and labelling was frequently associated with their outer, opaque layer or matter located outside the cells. Coating matter on vessel walls occurred at all stages of infection, and IEs only in later stages. IEs were delineated by opaque, often folded bands, some contouring pit borders, and contained membranous and vesicular structures mixed with other fine components. Only then, IEs were strongly but not uniformly labelled for chitin. Coating, IE-delineating bands, and the opaque outer layer of typical fungal cells were texturally similar, not labelled for chitin or cellulose, except where they impinged upon host walls. Both probes for chitin and cellulose strongly attached to vessel secondary walls. IEs were often confluent with coating, and with fungal cells connected to them by means of microfilamentous structures. Similar microfilamentous structures and opaque bands connected to IEs, the coating, and the microhyphae, or protruding from fungal cells reached into host walls, associated with alterations of these walls. The possible malleable IEs might be a counterpart of the coating, and although they do not occur in the initial stages of the disease, they could play an important role in the final stages of tissue degradation.

scholarly journals Treatment with the Mycoparasite Pythium oligandrum Triggers Induction of Defense-Related Reactions in Tomato Roots When Challenged with Fusarium oxysporum f. sp. radicis-lycopersici

1997 ◽  
Vol 87 (1) ◽  
pp. 108-122 ◽  
Author(s):  
Nicole Benhamou ◽  
Patrice Rey ◽  
Mohamed Chérif ◽  
John Hockenhull ◽  
Yves Tirilly
Keyword(s):  
Plant Defense ◽  
Fusarium Oxysporum ◽  
Host Cell ◽  
Cell Walls ◽  
Pythium Oligandrum ◽  
Tomato Plants ◽  
Host Cytoplasm ◽  
Defense Reactions ◽  
Tomato Roots ◽  
Root Tissues

The influence exerted by the mycoparasite Pythium oligandrum in triggering plant defense reactions was investigated using an experimental system in which tomato plants were infected with the crown and root rot pathogen Fusarium oxysporum f. sp. radicis-lycopersici. To assess the antagonistic potential of P. oligandrum against F. oxysporum f. sp. radicis-lycopersici, the interaction between the two fungi was studied by scanning and transmission electron microscopy (SEM and TEM, respectively). SEM investigations of the interaction region between the fungi demonstrated that collapse and loss of turgor of F. oxysporum f. sp. radicis-lycopersici hyphae began soon after close contact was established with P. oligandrum. Ultrastructural observations confirmed that intimate contact between hyphae of P. oligandrum and cells of the pathogen resulted in a series of disturbances, including generalized disorganization of the host cytoplasm, retraction of the plasmalemma, and, finally, complete loss of the protoplasm. Cytochemical labeling of chitin with wheat germ agglutinin (WGA)/ovomucoid-gold complex showed that, except in the area of hyphal penetration, the chitin component of the host cell walls was structurally preserved at a time when the host cytoplasm had undergone complete disorganization. Interestingly, the same antagonistic process was observed in planta. The specific labeling patterns obtained with the exoglucanase-gold and WGA-ovomucoid-gold complexes confirmed that P. oligandrum successfully penetrated invading cells of the pathogen without causing substantial cell wall alterations, shown by the intense labeling of chitin. Cytological investigations of samples from P. oligandrum-inoculated tomato roots revealed that the fungus was able to colonize root tissues without inducing extensive cell damage. However, there was a novel finding concerning the structural alteration of the invading hyphae, evidenced by the frequent occurrence of empty fungal shells in root tissues. Pythium ingress in root tissues was associated with host metabolic changes, culminating in the elaboration of structural barriers at sites of potential fungal penetration. Striking differences in the extent of F. oxysporum f. sp. radicis-lycopersici colonization were observed between P. oligandrum-inoculated and control tomato plants. In control roots, the pathogen multiplied abundantly through much of the tissues, whereas in P. oligandrum-colonized roots pathogen growth was restricted to the outermost root tissues. This restricted pattern of pathogen colonization was accompanied by deposition of newly formed barriers beyond the infection sites. These host reactions appeared to be amplified compared to those seen in nonchallenged P. oligandrum-infected plants. Most hyphae of the pathogen that penetrated the epidermis exhibited considerable changes. Wall appositions contained large amounts of callose, in addition to be infiltrated with phenolic compounds. The labeling pattern obtained with gold-complexed laccase showed that phenolics were widely distributed in Fusarium-challenged P. oligandrum-inoculated tomato roots. Such compounds accumulated in the host cell walls and intercellular spaces. The wall-bound chitin component in Fusarium hyphae colonizing P. oligandrum-inoculated roots was preserved at a time when hyphae had undergone substantial degradation. These observations provide the first convincing evidence that P. oligandrum has the potential to induce plant defense reactions in addition to acting as a mycoparasite.

scholarly journals First Report of Fusarium Wilt of Cilantro Caused by Fusarium oxysporum in California

Plant Disease ◽  
2005 ◽  
Vol 89 (10) ◽  
pp. 1130-1130 ◽  
Author(s):  
S. T. Koike ◽  
T. R. Gordon
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Vascular Tissue ◽  
Fusarium Species ◽  
Wilt Disease ◽  
Apium Graveolens ◽  
Peat Moss ◽  
State University ◽  
First Report ◽  
Vascular Discoloration

Cilantro, or coriander (Coriandrum sativum), is a leafy vegetable in the Apiaceae and is grown commercially in California primarily for use as a fresh herb. During 2002 and 2003 in coastal California (Santa Barbara County), commercial cilantro fields showed symptoms of a wilt disease. Affected plants grew poorly and were stunted. Lower foliage turned yellow with reddish tinges, and plants wilted during warmer times of the day. The main stem, crown, and taproot exhibited vascular discoloration that was reddish to light brown. As disease progressed, plants eventually died. For both years, the disease distribution was limited to isolated small patches (each patch measuring less than 1 m2 in area). A fungus was consistently isolated from symptomatic vascular tissue in crowns and taproots. On the basis of colony and conidial morphology, the isolates were identified as Fusarium oxysporum (2). No other fungi or bacteria were recovered from these plants. To test pathogenicity, suspensions containing 1 × 106 conidia/ml were prepared for five isolates. The roots of 30-day-old cilantro plants of four cultivars (30 plants each of Festival, Leisure, Santo, and LSO 14) were clipped and then soaked in the suspensions for 20 min. The roots of 30 plants of each cultivar were soaked in water as a control. Plants were repotted into new redwood bark + peat moss rooting medium and maintained in a greenhouse setting at 24 to 26°C. After 1 month, 95% or more of the inoculated plants showed yellowing and vascular discoloration symptoms similar to those seen in the field. F. oxysporum was reisolated from all inoculated plants. The four cilantro cultivars did not show differences in disease severity. Control plants showed no symptoms, and the fungus was not recovered from these plants. The experiment was repeated and the results were the same. Experiments also were conducted to determine if cilantro isolates could cause disease in celery (Apium graveolens var. dulce). Celery transplants and cilantro seedlings were prepared and inoculated as described above. However, after 2 months, celery plants did not show any disease symptoms, while the cilantro developed wilt symptoms and eventually died. A Fusarium wilt disease has been reported on coriander in Argentina and India where the pathogen was named F. oxysporum f. sp. coriandrii (1,3). To our knowledge, this is the first report of Fusarium wilt of cilantro in California. References: (1) M. Madia et al. Fitopatologia 34:155, 1999. (2) P. E. Nelson et al. Fusarium species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (3) U. S. Srivastava. Indian Phytopathol. 22:406, 1969.

scholarly journals First Report of Race 2 of Fusarium oxysporum f. sp. lycopersici, the Causal Agent of Fusarium Wilt on Tomato in Taiwan

Plant Disease ◽  
2006 ◽  
Vol 90 (1) ◽  
pp. 111-111 ◽  
Author(s):  
Z. M. Sheu ◽  
T. C. Wang
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Banding Pattern ◽  
Vascular Tissue ◽  
First Report ◽  
Intergenic Spacer Region ◽  
Stunted Growth ◽  
Vascular Discoloration ◽  
Race 1 ◽  
Race 2

Fusarium wilt caused by Fusarium oxysporum Schlechtend.:Fr. f. sp. lycopersici (Sacc.) W.C. Snyder & N.H. Hans. is a destructive disease of tomato crops worldwide. The use of resistant varieties is the best strategy for disease control. There are three reported races of the pathogen. Recent surveys indicated that many of the commercial cultivars with resistance to F. oxysporum f. sp. lycopersici race 1 planted in Taiwan displayed Fusarium wilt symptoms. Yellowing on the older leaves was observed on one side of the stems close to fruit maturity. The yellowing gradually affected most of the foliage and was accompanied by wilting of the plants. The vascular tissue was usually dark brown and discoloration extended to the apex. The wilting became more extensive until plants collapsed and died. A total of 87 isolates obtained from typical diseased plants throughout Taiwan from 2002 to 2005 were analyzed to determine the race and distribution of this pathogen in Taiwan. Isolates were confirmed at the species level using F. oxysporum-specific primers FOF1 and FOR1 (4). Subsequently, isolates were characterized for pathogenicity, race and restriction fragment length polymorphisms of the intergenic spacer region of rDNA (IGS-RFLP) with two reference isolates, Fol 11A (race 1) and Fol 34-1 (race 2). Pathogenicity tests and race determination were conducted using root-dip inoculation (3) on 2-week-old seedlings of host differentials Bonny Best (no resistance), UC82-L (resistant to race 1), and Florida MH-1 (resistant to races 1 and 2). Thirty-six seedlings of each cultivar were arranged into three replications and inoculated with each isolate. Disease reaction was evaluated 3 weeks after inoculation. The disease severity rating (DSR) was determined on individual plants according to the following scale: 0 = plant healthy without external symptoms; 1 = slight vascular discoloration with or without stunted growth; 2 = severe vascular discoloration usually with stunted growth; and 3 = plant wilted beyond recovery or dead. The presence of severe vascular discoloration indicated a susceptible reaction. All isolates were race 2, and over 70% of the isolates showed strong virulence with a DSR >2 on cvs. Bonny Best and UC-82L. This result was different from a previous report of race 1 from Taiwan (2). Two IGS-RFLP haplotypes generated by EcoRI, RsaI, and HaeIII digestions (1) were identified. Eighty-six isolates displayed one banding pattern, and one unique isolate displayed a second banding pattern. The results demonstrated the predominance of race 2 and low diversity within the Taiwan population. To our knowledge, this is the first report regarding the predominant race and IGS-RFLP haplotype identification of F. oxysporum f. sp. lycopersici in Taiwan. Our study indicates that tomato varieties in Taiwan should possess resistance to race 2. References: (1) G. Cai et al. Phytopathology 93:1014, 2003. (2) K. S. Elias and R. W. Schneider. Phytopathology 82:1421, 1992. (3) J. W. Gerdemann and A. M. Finley. Phytopathology 41:238, 1951. (4) P. K. Mishra et al. FEMS Microbiol. Lett. 218:329, 2003.

Resistant responses in juvenile seedlings of Pinus densiflora (Japanese red pine) inoculated with Endocronartium harknessii

1989 ◽  
Vol 67 (12) ◽  
pp. 3545-3552 ◽  
Author(s):  
A. A. Hopkin ◽  
P. V. Blenis ◽  
Y. Hiratsuka
Keyword(s):  
Host Cell ◽  
Vascular Tissue ◽  
Pinus Densiflora ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Cortical Cells ◽  
Host Cell Death ◽  
Endocronartium Harknessii ◽  
Infected Cells ◽  
Endodermal Cells

Hypocotyls of Pinus densiflora, a species known to be resistant to western gall rust, were inoculated with Endocronartium harknessii and examined by light and electron microscopy. Host cells, when initially infected, were apparently unaffected, as were the haustoria within them. Seedlings were observed to respond to infection in two ways. In the first type of response, infected cells showed signs of necrosis by 9 days after inoculation, although infecting haustoria appeared normal. By 18 days, most cortical cells in the centre of the infected region were necrotic, as were the haustoria within them. Infected cells at the colony margin still appeared healthy, indicating that host cell necrosis lagged behind infection and only occurred after the haustorium was established. Four weeks after inoculation, a ring of suberized and lignified endodermal cells separated the infected cortex from the uninfected vascular tissue and appeared to prevent further inward growth of the fungus. The second response type involved production of encapsulations around haustoria. Encapsulations appeared to have formed after haustoria senescence and were eventually followed by host cell death.

scholarly journals First Report of Fusarium oxysporum f. sp. lycopersici Race 2 on Tomato in Italy

Plant Disease ◽  
1999 ◽  
Vol 83 (10) ◽  
pp. 967-967 ◽  
Author(s):  
V. M. Stravato ◽  
R. Buonaurio ◽  
C. Cappelli
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Vascular Tissue ◽  
Morphological Features ◽  
Pathogenicity Test ◽  
First Report ◽  
Fungal Isolates ◽  
Race 1 ◽  
Race 2 ◽  
I Gene

During the summer of 1997, symptoms of Fusarium wilt were observed on tomato (Lycopersicon esculentum Mill.) cvs. Monica F1 and PS 110, which bear the I gene for resistance to race 1 of Fusarium oxysporum Schlechtend.:Fr. f. sp. lycopersici (Sacc.) W.C. Snyder & H.N. Hans., in two commercial production greenhouses in Latium (Fondi) and one greenhouse in Sardinia (Oristano). Infected plants showed yellowing, stunting, vascular discoloration, and premature death. A fungus from tomato stems with discolored vascular tissue was consistently isolated on potato dextrose agar (PDA) and, based on morphological features, was identified as F. oxysporum. To verify the pathogenicity of four fungal isolates, cv. Bonny Best tomato plants, which do not carry genes for Fusarium wilt resistance, were inoculated by dipping roots of 2-week-old seedlings in a suspension of 105 microconidia per ml for 30 s. Inocula were obtained from 1-week-old fungal cultures grown on PDA. Roots of control plants were dipped in water. Seedlings were transplanted to pots containing peat and river sand (1:1, vol/vol) and placed in a greenhouse at 20 to 25°C. One month after inoculation, all fungal isolates provoked wilting of inoculated plants. No symptoms were observed on control plants. The morphological features of the fungus reisolated from diseased plants were similar to those of the original isolates. Based on the pathogenicity test, we concluded that the fungal isolates belong to F. oxysporum f. sp. lycopersici. To determine the races of the fungal isolates, differential tomato lines VFN8 (I gene for resistance to race 1), Florida MH-1 (I and I2 genes for resistance to races 1 and 2), and I3R (I, I2, and I3 genes for resistance to races 1, 2, and 3) were inoculated with the four fungal isolates, using the same procedure described for the pathogenicity test. Because disease symptoms were detected on VFN8 but not on Florida MH-1 and I3R, we deduced that the fungal isolates belong to F. oxysporum race 2. This is the first report of F. oxysporum f. sp. lycopersici race 2 in Italy. Previous research indicated that race 1 is present in Italy (1). Currently, many commercially acceptable cultivars resistant to races 1 and 2 are available to Italian greenhouse growers. Reference: (1) M. Cirulli. Phytopathol. Mediterr. 4:63, 1965.

Biodegradable polyester neuroprostheses promote the reconnection of separated peripheral nerve stubs

1992 ◽  
Vol 50 (2) ◽  
pp. 1094-1095
Author(s):  
Beverly L. Giammara ◽  
Jennifer S. Stevenson ◽  
Peggy E. Yates ◽  
Robert H. Gunderson ◽  
Jacob S. Hanker
Keyword(s):  
Image Analysis ◽  
Basement Membrane ◽  
Periodic Acid ◽  
Light And Electron Microscopy ◽  
Computer Assisted ◽  
Type Iii Collagen ◽  
Image Analysis System ◽  
Biodegradable Polyester ◽  
Adult Rats ◽  
Type Iv

An 11mm length of sciatic nerve was removed from 10 anesthetized adult rats and replaced by a biodegradable polyester Vicryl™ mesh sleeve which was then injected with the basement membrane gel, Matrigel™. It was noted that leg sensation and movement were much improved after 30 to 45 days and upon sacrifice nerve reconnection was noted in all animals. Epoxy sections of the repaired nerves were compared with those of the excised segments by the use of a variation of the PAS reaction, the PATS reaction, developed in our laboratories for light and electron microscopy. This microwave-accelerated technique employs periodic acid, thiocarbohydrazide and silver methenamine. It stains basement membrane or Type IV collagen brown and type III collagen (reticulin), axons, Schwann cells, endoneurium and perineurium black. Epoxy sections of repaired and excised nerves were also compared by toluidine blue (tb) staining. Comparison of the sections of control and repaired nerves was done by computer-assisted microscopic image analysis using an Olympus CUE-2 Image Analysis System.

Isolation and characterization of cell walls from the mesocarp of mature grape berries (Vitis vinifera)

2020 ◽  
Author(s):  
KJ Nunan ◽  
Ian Sims ◽  
A Bacic ◽  
SP Robinson ◽  
GB Fincher
Keyword(s):  
Vitis Vinifera ◽  
Cell Walls ◽  
Vascular Tissue ◽  
Compositional Analysis ◽  
Water Soluble ◽  
Vitis Vinifera L ◽  
Nylon Mesh ◽  
Cytoplasmic Material ◽  
Isolation And Characterization ◽  
Tissue Homogenates

Cell walls have been isolated from the mesocarp of mature grape (Vitis vinifera L.) berries. Tissue homogenates were suspended in 80% (v/v) ethanol to minimise the loss of water-soluble wall components and wet-sieved on nylon mesh to remove cytoplasmic material. The cell wall fragments retained on the sieve were subsequently treated with buffered phenol at pH 7.0, to inactivate any wall-bound enzymes and to dislodge small amounts of cytoplasmic proteins that adhered to the walls. Finally, the wall preparation was washed with chloroform/methanol (1:1, v/v) to remove lipids and dried by solvent exchange. Scanning electron microscopy showed that the wall preparation was essentially free of vascular tissue and adventitious protein of cytoplasmic origin. Compositional analysis showed that the walls consisted of approximately 90% by weight of polysaccharide and less than 10% protein. The protein component of the walls was shown to be rich in arginine and hydroxyproline residues. Cellulose and polygalacturonans were the major constituents, and each accounted for 30-40% by weight of the polysaccharide component of the walls. Substantial varietal differences were observed in the relative abundance of these two polysaccharides. Xyloglucans constituted approximately 10% of the polysaccharide fraction and the remainder was made up of smaller amounts of mannans, heteroxylans, arabinans and galactans.

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