Effects of vesicular-arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to internal cytokinin concentrations

Relations between cytokinin concentrations and effects of P and vesicular-arbuscular mycorrhizal (VAM) infection were investigated in Plantago major L. ssp. pleiosperma Pilger. Both mycorrhizal infection by Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe and P addition increased the shoot to root ratio, specific leaf area (SLA), and P concentrations of shoot and roots, and decreased the percentage of dry matter in the shoot during the experiment. In general, P concentration in the shoot and roots of each treatment correlated positively with the shoot to root ratio and specific leaf area, and negatively with the percentage of dry matter in the shoot. Cytokinin concentrations in the tissue of shoots and roots were determined using an enzyme-linked immunosorbent assay. Concentrations of zeatin and zeatin-ribosides in the free base and nucleotide fractions had increased more after P addition than in the case of mycorrhizal infection in both shoot and roots, whereas the P concentrations had increased less. It is suggested that zeatin and zeatin-ribosides are not the primary growth-substances involved in mediating VAM effects.     

Growth of arbuscular mycorrhizal mycelium in calcareous dune sand and its interaction with other soil microorganisms as estimated by measurement of specific fatty acids

Fatty acid analysis was used for determining the extent of the development of the external mycelium of AM fungi (mixed inoculum from a sand dune) growing from roots of Festuca rubra and Plantago lanceolata in calcareous dune sand. The plants were raised in chambers specially designed to permit the growth of AM mycelium in root-free compartments. In two separate experiments, growth of external mycelium in the root-free compartments was detected and the amount of mycelium was estimated using the indicator of AM fungal biomass, phospholipid fatty acid (PLFA) 16:15. The results showed that the PLFA 16:15 was suitable for estimating the mycelium emerging from the mixed inoculum obtained from the field roots of F. rubra and P. lanceolata.The PLFA 16:15 showed external mycelium to become established in the root-free compartments within a period of 3 weeks and the amount of mycelium to continue to increase at 6 and 9 weeks. Increases in neutral lipid fatty acid (NLFA) 16:15 (indicator of storage lipids) over time were inconsistent between the two experiments, but appeared to follow patterns of sporulation in each experiment.In both experiments, the root-free compartment was colonised by saprophytic fungi to a greater extent in the case of non-mycorrhizal than of AM treatment, as indicated by an increase in PLFA 18:26,9 (indicator of saprophytic fungi). The absence of an increase in the case of AM treatment indicates that AM fungal mycelium can negatively affect the growth of saprophytic fungi in this soil type. This result was, however, only weakly supported by measurements of ergosterol content. The analysis of bacteria specific PLFAs showed that bacterial biomass was not affected by the AM mycelium.     

Vesicular arbuscular mycorrhizal fungi improves establishment of micropropagated Leucaena leucocephala plantlets

Investigations were carried out to achieve cent per cent transplantation success of micropropagated Leucaena leucocephala (a fast growing multipurpose leguminous tree species) plantlets using two vesicular arbuscular mycorrhizal fungi, Glomus fasciculatum and Glomus macrocarpum. Plantlets were obtained by rooting the shoots [obtained through; hypocotyl callus in presence of 10^-5M BAP + 10^-6M NAA; and axillary bud sprouting from cotyledonary and other nodes in presence of 10^-5M BAP, on Gamborg's B5 medium], on half strength B5 medium supplemented with 5×10^-6M IBA. Subsequent to the nodulation of their roots with Rhizobium (strain PRGL 001)in soilrite, these plantlets were tranferred to sterilized garden soil by laying inoculum of either Glomus fasciculatum or Glomus macrocarpum around their roots. Only 20% of the plantlets survived in soils lacking VAM fungus. In contrast, cent per cent of the plantlets of Leucaena leucocephala established very well and showed good growth in VAM inoculated soil. Roots of the later plantlets showed presence of both external and internal hyphae with well formed arbuscules and vesicles confirming the establishment of good mycorrhizal association. These studies convincingly demonstrate that the mycorrhizal association help in successful establishment of tissue culture raised plantlets of Leucaena leucocephala in the field conditions by alleviating the transplantation shock. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of vesicular-arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to the internal phosphate concentration

Two experiments were carried out to study physiological effects of vesicular-arbuseular mycorrhizal infection on Plantago major L., ssp. pleiosperma (Pilger). In the first experiment, infection by the Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe increased growth, shoot to root ratio, P concentrations in both shoot and roots and total uptake of P per plant. The percentages of dry matter in both shoot and roots were lower in mycorrhizal plants.
In the second experiment different P treatments were applied to both mycorrhizal and non-mycorrhizal P. major plants to separate any effects of mycorrhizal infection from increased uptake of P. In addition to the effects found in the first experiment, mycorrhizal, P, and mycorrhizal x P interaction effects were found on root respiration rate and the concentration of soluble sugars in the roots. No clear effects on total dry weight, N and starch concentrations in shoot and roots and sugar concentraion in the shoot were found. Irrespective of the mycorrhizal treatment, increased P concentration in the shoot correlated with an increased shoot to root ratio and root respiration rate, and a decreased percentage dry matter and sugar concentration in the roots. However, the root respiration rate and the P concentration in the roots of mycorrhizal plants were enhanced more than expected from the increased P concentrations in the shoots of these plants.     

Glomus fasciculatum alleviates transplantation shock of micropropagated Sesbania sesban

Investigations were carried out using the vesicular arbuscular mycorrhizal fungus, Glomus fasciculatum, to improve the success in transplanting micropropagated plantlets of Sesbania sesban. Plantlets were developed from somatic embryos and/or adventitious buds (induced from various explants on Gamborg's medium supplemented with 6-benzylaminopurine), in the presence of 10^–7 m α-naphthaleneacetic acid and 5×10^–6 m gibberellic acid. Subsequent to nodulating the roots with Rhizobium, plantlets were transplanted into sterile garden soil and inoculated with or without G. fasciculatum. Only 30% of plantlets transferred to soil without G. fasciculatum survived. In contrast, all the plantlets inoculated with G. fasciculatum survived. Histochemical study revealed the presence of intracellular hyphae with well-developed arbuscules and intercellular hyphae with vesicles, suggesting that G. fasciculatum formed a good mycorrhizal association with S. sesban roots. These observations showed that mycorrhizal association helped to increase the potential of micropropagated plantlets to successfully withstand transplantation shock. Received: 6 January 1997 / Revision received: 28 August 1997 / Accepted: 5 September 1997     

4种(变种)辣椒的核型研究

本文研究了辣椒属4种(变种)的核型,各个种的核型可简式为小米辣2n=24=23m+1sm:簇生辣2n=24=20m+2sm+2st:樱桃辣2n=24=20m+4sm(2SAT):“印度辣”2n=24=22m+2st。按照Stebbins的核型分类,小米辣为2A型;簇生辣和樱桃辣为2A型,印度辣为2B型。     

Effects of phosphorus application and mycorrhizal inoculation on root characteristics of subterranean clover and ryegrass in relation to phosphorus uptake

The effects of phosphorus (P) application and mycorrhizal inoculation on the root characteristics of subterranean clover and ryegrass were examined. Phosphorus application increased total root length, root surface area and root volume of both plant species. In contrast, mycorrhizal infection only affected the root characteristics of subterranean clover. Ryegrass took up more P than non-mycorrhizal subterranean clover at all levels of application. However, mycorrhizal infection only increased P uptake by subterranean clover and there was no difference in P uptake between ryegrass and mycorrhizal subterranean clover at low levels of P application. When the P uptake was expressed on the basis of any of the root characteristics, subterranean clover were superior to ryegrass suggesting that the greater uptake of P by ryegrass is not due to a higher efficiency in absorption of P from soil solution, but rather to a large root system.     

Mineral and lipid composition of Glycine - Glomus - Bradyrhizobium symbioses

Soybean [Glyeine max (L.) Merr. cv. Amsoy 71] plants were inoculated with either the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum. with a strain of Bradyrizobobium Japonicum. or with both endophytes in combintion. Noninoculated controlplantes were fertilized with levels of N and P previously found to compensate for nutrient input following infection by Bradyhizobium or Glomus Temporal differences in N and P assimilation in nodulated or mycorrhizal plants indicated that Glomus was most effective during early vegetative growth and Bradyrhizobion was active until the mid-pod-fill stage in soybean. In general. soybeans colonized by Glomus contained more Cu but less Mn and P than corresponding P-fertilized plants. Soyubean roots infected with G. fasciculaum contained five unusual fatty acids: [16: 1 (11c): 8:3 (6c, 9c, 12c): 20:3 (8c, 11c, 14c): 20:4 (5c, 8c, 11c, 14c): 20:5 (5c, 8c, 11c, 14c, 17c)] that were absent in non-infected roots. Fatty acid 16:1 (11c) comprised 43% of total fatty acids in Glomus-infected roots at week 9 and 29% of total root fatty acids at week 15. This isomer of hexadecenoic acid was positively correlated with vesicle number (r = 0.92**). and 16:1 (11c) was probably the principalstorage fatty acid in fungal vesicles. These five unusual fatty acids were not found in the leaves. pods or seeds of either VAM or non-VAM plants. Specific leaf area increased with time in nodulated soybeans. but these plants contained lessCu than corresponding N-fertilized plants. Soybeans nodulated with Bradyrthizobium contained more total lipid and proportionately more fatty acid 16:0 than N-fertilized plants. Infection by Glomus or Bradyrhizobium also altered the fatty acid composition of above-ground plant parts, although these changes were subtle compared to the markedly different fatty acid found in Glomus-infected roots. These findings suggest that seed quality may be altered due to the physiological changes resulting from infection by N²-fixing bacteria and/or endomycorrhizal fungi. Observed differences in the plant nutrition of inoculated soybeans could not be replicated by fertilizer addition alone.     

Mycorrhizae in Adenostoma fasciculatum Hook. & Arn.: a combination of unusual ecto- and endo-forms

 The mycorrhizal status of Adenostoma fasciculatum, the dominant shrub in California chaparral, has been unclear. In two typical, nearly monospecificstands, A. fasciculatum was found to have arbuscules and intercellular hyphae. Antisera detected hyphae of the arbuscular mycorrhizal (AM) fungal genera Acaulospora, Glomus, and Scutellospora, although we found only spores of Glomus. Some roots had partial sheaths and inter- and intracellular septate fungi without indications of root necrosis. Ectomycorrhizal root tips were also found, including Cenococcum and other unknown taxa. Sporocarps of EM fungi including species of Rhizopogon, Pisolithus, Balsamia, Laccaria, Hygrophorus, and Cortinarius were found in the stand, with no other EM or arbutoid mycorrhizal plants nearby. These observations indicate that A. fasciculatum forms mycorrhizae with AM, septate, and EM fungi, but often fails to form easily recognizable mycorrhizal structures. Accepted: 5 September 1998     

Chib1和PAL5基因在AM真菌Glomus fasciculatus诱导大豆抗线虫病害防御反应中的作用

本研究系统分析了大豆（品种：‘鲁豆4’）接种AM真菌Glomus fasciculatum和胞囊线虫（SCN,Heterodera glycines）4号生理小种后各处理菌根和线虫侵染率、几丁质酶和苯丙氨酸解氨酶（PAL）活性及几丁质酶基因Chib1和苯丙氨酸解氨酶基因PAL5转录物的动态变化。结果表明,接种SCN对AM真菌的侵染率没有产生显著影响,但先接种AM真菌后接种SCN的大豆根内线虫侵染率明显低于只接种SCN的处理。另外,先接种AM真菌后接种SCN的大豆根内几丁质酶和PAL活性显著提高,活性高峰出现在接种线虫后的第3天。值得注意的是,先接种AM真菌后接种SCN的大豆根内两种基因Chib1和PAL5转录物高峰也出现在接种SCN后的第3天,即AM真菌侵染率快速上升而SCN侵染率快速下降时期。所以Chib1和PAL5基因的表达可能是AM真菌诱导的抗大豆胞囊线虫病害防御反应的一种表现。因此推测Chib1和PAL5直接参与了AM真菌诱导大豆抗胞囊线虫病害的防御反应。