Interactive effects of temperature and arbuscular mycorrhizal fungi on growth,P uptake and root respiration of<Emphasis Type="Italic"> Capsicum annuum</Emphasis> L.

Capsicum annuum (pepper) plants were inoculated with the arbuscular mycorrhizal (AM) fungi Glomus intraradices Smith and Schenck, an undescribed Glomus sp. (AZ 112) or a mixture of these isolates. Control plants were non-mycorrhizal. Plants were grown for 8 weeks at moderate (20.7–25.4°C) or high (32.1–38°C) temperatures. Colonization of pepper roots by G. intraradices or the Glomus isolate mixture was lower at high than at moderate temperatures, but colonization by Glomus AZ112 was somewhat increased at high temperatures. Pepper shoot and root dry weights and leaf P levels were affected by an interaction between temperature and AM fungal treatments. At moderate temperatures, shoot dry weights of plants colonized by the Glomus isolate mixture or non-AM plants were highest, while root dry weights were highest for non-AM plants. At high temperatures, plants colonized by Glomus AZ112 or the non-AM plants had the lowest shoot and root dry weights. AM plants had generally higher leaf P levels at moderate temperatures and lower P levels at high temperatures than non-AM plants. AM plants also had generally higher specific soil respiration than non-AM plants regardless of temperature treatment. At moderate temperatures, P uptake by all AM plants was enhanced relative to non-AM plants but there was no corresponding enhancement of growth, possibly because less carbon was invested in root growth or root respiratory costs increased. At high temperatures, pepper growth with the G. intraradices isolate and the Glomus isolate mixture was enhanced relative to non-AM controls, despite reduced levels of AM colonization and, therefore, apparently less fungal P transfer to the plant.     

Differential effects of <Emphasis Type="Italic">Paenibacillus</Emphasis> spp. on cucumber mycorrhizas

The effects of 17 Paenibacillus strains on root colonization by Glomus intraradices or Glomus mosseae and plant growth parameters (shoot and root weight) of mycorrhizal cucumber plants were examined. The Paenibacillus strains were originally isolated from mycorrhizal (G. intraradices) and non-mycorrhizal cucumber rhizosphere and/or hyphosphere, except for strain EJP73, which originated from a Pinus sylvestris-Lactarius rufus ectomycorrhiza. Root colonization of cucumber plants by G. intraradices or G. mosseae was unaffected by all seven strains of Paenibacillus polymyxa, but was decreased or increased by four strains of Paenibacillus macerans and strain EJP73 of Paenibacillus sp. Overall, shoot dry weight of cucumber grown in symbioses with either G intraradices or G. mosseae was unaffected by inoculation with all of the Paenibacillus strains, except for strain MB02-429 of P. macerans, which increased the shoot dry weight in the cucumber-G. mosseae symbiosis. On the other hand, several Paenibacillus strains caused altered root growth. Three strains of P. polymyxa and four strains of P. macerans increased the root fresh weight of the cucumber–G. intraradices symbiosis, whereas three strains of P. polymyxa and one strain of P. macerans as well as Paenibacillus sp. EJP73, decreased the root fresh weight of the cucumber–G. mosseae symbiosis. In conclusion, our results show that bacteria from several species of Paenibacillus differentially affect cucumber mycorrhizas.     

Influence of Salinity on the <Emphasis Type="Italic">In Vitro</Emphasis> Development of <Emphasis Type="Italic">Glomus intraradices</Emphasis> and on the <Emphasis Type="Italic">In Vivo</Emphasis> Physiological and Molecular Responses of Mycorrhizal Lettuce Plants

Increased salinization of arable land is expected to have devastating global effects in the coming years. Arbuscular mycorrhizal fungi (AMF) have been shown to improve plant tolerance to abiotic environmental factors such as salinity, but they can be themselves negatively affected by salinity. In this study, the first in vitro experiment analyzed the effects of 0, 50, or 100 mM NaCl on the development and sporulation of Glomus intraradices. In the second experiment, the effects of mycorrhization on the expression of key plant genes expected to be affected by salinity was evaluated. Results showed that the assayed isolate G. intraradices DAOM 197198 can be regarded as a moderately salt-tolerant AMF because it did not significantly decrease hyphal development or formation of branching absorbing structures at 50 mM NaCl. Results also showed that plants colonized by G. intraradices grew more than nonmycorrhizal plants. This effect was concomitant with a higher relative water content in AM plants, lower proline content, and expression of Lsp5cs gene (mainly at 50 mM NaCl), lower expression of the stress marker gene Lslea gene, and lower content of abscisic acid in roots of mycorrhizal plants as compared to nonmycorrhizal plants, which suggest that the AM fungus decreased salt stress injury. In addition, under salinity, AM symbiosis enhanced the expression of LsPIP1. Such enhanced gene expression could contribute to regulating root water permeability to better tolerate the osmotic stress generated by salinity.     

Effect of <Emphasis Type="Italic">Glomus</Emphasis> species on physiology and biochemistry of <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

The present study on efficacy of different Glomus species, an arbuscular mycorrhizal (AM) fungus (G. aggregatum, G. fasciculatum, G. mosseae, G. intraradices) on various growth parameters such as biomass, macro and micronutrients, chlorophyll, protein, cytokinin and alkaloid content and phosphatase activity of pink flowered Catharanthus roseus plants showed that all Glomus species except G. intraradices enhanced the chlorophyll, protein, crude alkaloid, phosphorus, sulphur, manganese and copper contents of C. roseus plants along with phosphatase activity significantly over uninoculated plants. However only G. mosseae and G. fasciculatum exhibited superior symbiotic relationship with the plant. G. mosseae was found to be the best for increasing the crude alkaloid content (8.19%) in leaf and also in increasing the quantity of important alkaloids vincristine and vinblastine.     

Interactions between<Emphasis Type="Italic"> Trichoderma pseudokoningii</Emphasis> strains and the arbuscular mycorrhizal fungi<Emphasis Type="Italic"> Glomus mosseae</Emphasis> and<Emphasis Type="Italic"> Gigaspora rosea</Emphasis>

The interaction between Trichoderma pseudokoningii (Rifai) 511, 2212, 741A, 741B and 453 and the arbuscular mycorrhizal fungi Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe BEG12 and Gigaspora rosea Nicolson & Schenck BEG9 were studied in vitro and in greenhouse experiments. All T. pseudokoningii strains inhibited the germination of G. mosseae and Gi. rosea except the strain 453, which did not affect the germination of Gi. rosea. Soluble exudates and volatile substances produced by all T. pseudokoningii strains inhibited the spore germination of G. mosseae. The germination of Gi. rosea spores was inhibited by the soluble exudates produced by T. pseudokoningii 2212 and 511, whereas T. pseudokoningii 714A and 714B inhibited the germination of Gi. rosea spores by the production of volatile substances. The strains of T. pseudokoningii did not affect dry matter and percentage of root length colonization of soybean inoculated with G. mosseae, except T. pseudokoningii 2212, which inhibited both parameters. However, all T. pseudokoningii strains decreased the shoot dry matter and the percentage of AM root length colonization of soybean inoculated with Gi. rosea. The saprotrophic fungi tested seem to affect AM colonization of root by effects on the presymbiotic phase of the AM fungi. No influence of AM fungi on the number of CFUs of T. pseudokoningii was found. The effect of saprotrophic fungi on AM fungal development and function varied with the strain of the saprotrophic species tested.     

Toxicity of diesel fuel to germination,growth and colonization of <Emphasis Type="Italic">Glomus intraradices</Emphasis> in soil and <Emphasis Type="Italic">in vitro</Emphasis> transformed carrot root cultures

Phytoremediation is the use of selected plants to decontaminate polluted environments. Arbuscular mycorrhizal fungi (AMF) may potentially be useful for phytoremediation, but it is not known how petroleum hydrocarbons influence AMF spore germination and hyphal growth. To address this question, germination of spores and germ tube growth of Glomus intraradices Schenck and Smith and Glomus aggregatum Schenck and Smith were assessed in soil contaminated with up to 3% (w/v) of F2 diesel oil or HAGO reference oil. Hyphal growth, colonization and progeny spore production were assessed in vitro using transformed root cultures of Daucus carota and G. intraradices spores in a F2 diesel contaminated medium. In addition, extraradical hyphal growth of G. intraradices colonizing Daucus carota in the presence of F2 diesel was studied. Neither F2 diesel nor HAGO reference oil affected spore germination or germ tube growth in soil. However, in the presence of plant roots, germ tube growth of G. intraradices was reduced and delayed in the presence of F2 diesel and root colonization was not detected. Hyphal growth of pre-colonized carrot roots by G. intraradices was reduced and delayed in F2 contaminated medium compared to controls. F2 diesel did not inhibit spore germination of these AMF species but did reduce colonization, germ tube and hyphal growth. These results suggest that AMF inoculum can be established in petroleum-contaminated sites. However, it may prove beneficial to plant pre-colonized plants to increase the probability of sufficient AMF colonization and growth. The likely mechanism(s) of petroleum toxicity in this plant-microbe system was discussed.     

<Emphasis Type="Italic">In vitro</Emphasis> propagation of <Emphasis Type="Italic">Gentiana dinarica</Emphasis> Beck.

Gentiana dinarica Beck, rare and endangered species of Balkan Dinaric alps, was in vitro propagated (micropropagated) from axillary buds of plants collected at Mt. Tara, Serbia. G. dinarica preferred MS to WPM medium, with optimal shoot multiplication on MS medium with 3% sucrose, 1.0 mg l⁻¹ BA and 0.1 mg l⁻¹ NAA. Rooting was not clearly separated from shoot multiplication since BA did not completely inhibit root initiation. Spontaneous rooting on plant growth regulator-free medium occurred in some 30% of shoot explants. Rooting was stimulated mostly by decreased mineral salt nutrition and a medium with 0.5 MS salts, 2% sucrose and 0.5–1.0 mg l⁻¹ IBA was considered to be optimal for rooting. Rooted plantlets were successfully acclimated and further cultured in peat-based substrate.     

<Emphasis Type="Italic">In vitro</Emphasis> regeneration of medicinal plant <Emphasis Type="Italic">Centella asiatica</Emphasis>

This paper describes multiple shoot regeneration from leaf and nodal segments of a medicinally important herb Centella asiatica L. on Murashige and Skoog’s (MS) medium supplemented with a range of growth regulators. The highest number of multiple shoots was observed on MS augmented with 3.0 mg dm⁻³ N⁶-benzylaminopurine (BAP) and 0.05 mg dm⁻³ α-naphthaleneacetic acid (NAA). Leaf explant showed maximum percentage of cultures regenerating shoots (81.6 %), with the highest shoot number (8.3 shoots per explant) and the shoot length (2.1 cm) whereas, nodal explant showed less number of shoots with callus formation at the base cut end. Successive shoot cultures were established by repeatedly sub-culturing the original explant on a fresh medium. Rooting of in vitro raised shoots was best induced on half strength MS supplemented with 0.5 mg dm⁻³ indole-3-butyric acid (IBA) with highest percentage of shoot regenerating roots (76.8 %) with 3–4 roots per shoot. Plantlets were acclimated in Vermi-compost and eventually established in soil. Contents of chlorophyll, total sugars, reducing sugars and proteins were estimated in leaf tissue from both in vivo and in vitro raised plants. Chlorophyll content was higher in in vivo plants, whereas other three components were higher in in vitro plants.     

Factors affecting <Emphasis Type="Italic">in vitro</Emphasis> propagation and field establishment of <Emphasis Type="Italic">Chlorophytum borivilianum</Emphasis>

The effect of plant growth regulators (PGRs), gelling agents, sucrose and heat shock on shoot multiplication, shoot growth, rooting and subsequent survival of Chlorophytum borivilianum Sant. et Fernand was evaluated. Benzyladenine (BA) was found to be better cytokinin over kinetin (KIN) for shoot multiplication. Sucrose concentrations from 116–290 mM in the basal medium (BM) promoted shoot multiplication. Heat shock (50 °C, 1 h) also promoted shoot multiplication at these sucrose concentrations on both BM medium and BM supplemented with 5.0 μM BA. Beneficial effect of sucrose was also observed on rooting of shoots on BM as well as BM supplemented with 5.0 μM indole-3-butyric acid (IBA). Phytagel as a gelling agent was found to be more effective for shoot proliferation and growth compared to agar. Amongst various soil mixtures tested, higher survival of plants was observed in soil containing Vermicompost. It was interesting to note that a maximum plant survival (> 95 %) was observed when plants were directly transferred to net-house (irradiance reduced to 50 % with green net, without humidity and temperature control) than poly-house (with humidity and temperature control). Random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) analysis of regenerated plants showed genetic similarity to mother plant.     

Comparison of conditions for mycelial growth of <Emphasis Type="Italic">Lepista sordida</Emphasis> causing fairy rings on <Emphasis Type="Italic">Zoysia matrella</Emphasis> turf to those on <Emphasis Type="Italic">Agrostis palustris</Emphasis> turf

Symptoms of fairy rings caused by Lepista sordida have been reported on Zoysiagrass (Zoysia spp.) turf maintained at fairway height (2 cm), but not on bentgrass (Agrostis spp.) maintained at putting green height (0.5 cm). The mycelia of this fungus inhabit primarily the upper 0–2 cm layer of the soil extending into the thatch. To compare conditions for the mycelial growth in Z. matrella turf to those in A. palustris turf, we examined the effects of nutrients, temperature, water potential, and pH in the field as well as in the laboratory. Greater growth of the mycelia was observed in medium that included hot water extracts from soil of the 0–1 cm zone in Z. matrella turf compared to that from A. palustris. The upper soil layer in Z. matrella turf contained more organic matter from clippings than that in A. palustris. The temperature and water potential of the 0–2 cm soil zone in Z. matrella turf were also more favorable for the mycelial growth. The soil pH values of this zone in Z. matrella turf were less favorable compared to A. palustris but within the range for accelerating mycelial growth. Part of this study was presented orally at the 46th meeting of the Mycological Society of Japan in 2002     

Contribution of <Emphasis Type="Italic">Glomus intraradices</Emphasis> inoculation to nutrient acquisition and mitigation of ionic imbalance in NaCl-stressed <Emphasis Type="Italic">Trigonella foenum-graecum</Emphasis>

The study aimed to investigate the effects of an AM fungus (Glomus intraradices Schenck and Smith) on mineral acquisition in fenugreek (Trigonella foenum-graecum) plants under different levels of salinity. Mycorrhizal (M) and non-mycorrhizal (NM) fenugreek plants were subjected to four levels of NaCl salinity (0, 50, 100, and 200 mM NaCl). Plant tissues were analyzed for different mineral nutrients. Leaf senescence (chlorophyll concentration and membrane permeability) and lipid peroxidation were also assessed. Under salt stress, M plants showed better growth, lower leaf senescence, and decreased lipid peroxidation as compared to NM plants. Salt stress adversely affected root nodulation and uptake of NPK. This effect was attenuated in mycorrhizal plants. Presence of the AM fungus prevented excess uptake of Na⁺ with increase in NaCl in the soil. It also imparted a regulatory effect on the translocation of Na⁺ ions to shoots thereby maintaining lower Na⁺ shoot:root ratios as compared to NM plants. Mycorrhizal colonization helped the host plant to overcome Na⁺-induced Ca²⁺ and K⁺ deficiencies. M plants maintained favorable K⁺:Na⁺, Ca²⁺:Na⁺, and Ca²⁺:Mg²⁺ ratios in their tissues. Concentrations of Cu, Fe, and Zn²⁺ decreased with increase in intensity of salinity stress. However, at each NaCl level, M plants had higher concentration of Cu, Fe, Mn²⁺, and Zn²⁺ as compared to NM plants. M plants showed reduced electrolyte leakage in leaves as compared to NM plants. The study suggests that AM fungi contribute to alleviation of salt stress by mitigation of NaCl-induced ionic imbalance thus maintaining a favorable nutrient profile and integrity of the plasma membrane.     

Combined effect of an arbuscular mycorrhizal fungus and a biocontrol bacterium against<Emphasis Type="Italic">Pythium ultimum</Emphasis> in soil

The combined effect of the arbuscular mycorrhizal (AM) fungusGlomus intraradices and the bacteriumBurkholderia cepacia onPythium ultimum was studied in a growth system with root-free soil compartments allowing examination of microbial interactions without direct interference from roots. Signature fatty acids were used to quantify individual microbial populations. Biomass and amount of energy reserves were estimated using specific phospholipid fatty acids (PLFA) and neutral lipid fatty acids (NLFA), respectively. Population density ofP. ultimum was estimated by colony forming units on selective media. Both biocontrol agents (BCAs) reduced population density ofP. ultimum. Biomass ofB. cepacia measured using signature fatty acids was inhibited by the presence of mycelium ofG. intraradices, which might explain why no additive effect onP. ultimum was found when combining the two BCAs. In conclusion, combiningG. intraradices andB. cepacia did not enhance the biocontrol efficacy againstP. ultimum.     

Arbuscular mycorrhiza confers Pb tolerance in <Emphasis Type="Italic">Calopogonium mucunoides</Emphasis>

Heavy metals (HMs) are environmental pollutants of great concern to humans because of their high potential toxicity. Lead is a HM that is present in the soil in very small amounts, but anthropogenic activities have increased its content in some locations, which can make these areas unproductive or inappropriate for crop production. However, there are some plants that can grow in contaminated soils and, thus, can be useful for the removal or stabilisation of such contaminants. In addition, plants that are not able to tolerate high concentrations of HMs in the soil can become tolerant or increase their performance when associated with arbuscular mycorrhizal (AM) fungi. Accordingly, this study was carried out to verify whether the inoculation of Glomus etunicatum, an AM fungus species, in Calopogonium mucunoides would influence plant tolerance to increasing concentrations of Pb in the soil. The experimental design was completely randomised, in a 2 × 4 factorial design, and the treatments consisted of inoculation (or not) with the AM fungus, G. etunicatum, and the addition of four Pb concentrations (0, 250, 500 or 1,000 mg kg⁻¹) to the soil. The results showed that the association of C. mucunoides with G. etunicatum promoted biomass production, and nutrient uptake (P, S and Fe) was also positively influenced by mycorrhization. The malondialdehyde content was higher in non-mycorrhizal leaves, suggesting a reduction in the damage to membranes by lipid peroxidation in plants associated with mycorrhizae. However, the Pb concentration in the shoots did not differ between the mycorrhizal and non-mycorrhizal plants. The results of our study suggest that the AM symbiosis can be considered very effective in contributing to the tolerance of C. mucunoides to Pb.     

Molecular Systematic Study of <Emphasis Type="Italic">Chrysosplenium</Emphasis> Series <Emphasis Type="Italic">Pilosa</Emphasis> (Saxifragaceae) in Korea

To address systematic issues pertaining to series Pilosa of Korean Chrysosplenium, the phylogenetic relationships of the 35 accessions of Korean Chrysosplenium taxa were examined using the DNA sequence data obtained from the nuclear ribosomal internal transcribed spacer (ITS) regions and the psbK-I gene of the plastid genome. The results from both ITS and psbK-I sequence data indicated that Chrysosplenium flaviflorum formed a well-supported clade that merits species status of the taxon. The ITS phylogenetic trees detected two distinct lineages in Chrysosplenium pilosum var. fulvum. Geographically, one lineage was widely distributed throughout the country whereas the other was confined to Gyeonggi and Gangwon provinces. The plants sampled from Jeju Island, which have been recognized as C. pilosum var. sphaerospermum [C. hallaisanense] exhibited no DNA sequence feature segregating them from C. pilosum var. fulvum [C. barbatum] distributed in the mainland area of Korea. The plastid DNA sequence data was not fully in concordance with the nuclear ribosomal ITS data and the current taxa delimitation. These results suggest incomplete lineage sorting or that plastid genome capture may have occurred during the evolution of some taxa examined in the present study.     

Morphological evaluation and antioxidant activity of <Emphasis Type="Italic">in vitro</Emphasis>- and <Emphasis Type="Italic">in vivo</Emphasis>-derived <Emphasis Type="Italic">Echinacea purpurea</Emphasis> plants

An effective in vitro protocol for rapid clonal propagation of Echinacea purpurea (L.) Moench through tissue culture was described. The in vitro propagation procedure consisted of four stages: 1) an initial stage - obtaining seedlings on Murashige and Skoog (MS) basal medium with 0.1 mg L⁻¹ 6-benzylaminopurine, 0.1 mg L⁻¹ α-naphthalene acetic acid and 0.2 mg L⁻¹ gibberellic acid; 2) a propagation stage — shoot formation on MS medium supplemented with 1 mg L⁻¹ 6-benzylaminopurine alone resulted in 9.8 shoots per explant and in combination with 0.1 mg L⁻¹ α-naphthalene acetic acid resulted in 16.2 shoots per explant; 3) rooting stage — shoot rooting on half strength MS medium with 0.1 mg L⁻¹ indole-3-butyric acid resulted in 90% rooted microplants; 4) ex vitro acclimatization of plants. The mix of peat and perlite was the most suitable planting substrate for hardening and ensured high survival frequency of propagated plants. Significant higher levels were observed regarding water-soluble and lipid-soluble antioxidant capacities (expressed as equivalents of ascorbate and α-tocopherol) and total pnenols content in extracts of Echinaceae flowers derived from in vitro propagated plants and adapted to field conditions in comparison with traditionally cultivated plants.     

Rhizospheric streptomycetes as potential biocontrol agents of <Emphasis Type="Italic">Fusarium</Emphasis> and <Emphasis Type="Italic">Armillaria</Emphasis> pine rot and as PGPR for <Emphasis Type="Italic">Pinus taeda</Emphasis>

Pinus taeda is one of the main timber trees in Brazil, occupying 1.8 million ha with an annual productivity of 25–30 m³ ha⁻¹. Another important species is Araucaria angustifolia, belonging to the fragile Rainforest biome, which for decades has been a major source of timber in Brazil. Some diseases that affect the roots and/or the stem of these trees and cause “damping-off” of the seedlings, with economic and environmental losses for the forest sector, are caused by the plant pathogenic fungi Fusarium sp. or Armillaria sp. This research project intended to isolate actinobacteria from the Araucaria rhizosphere, which present an antagonistic effect against these fungi. After the selection of the best pathogen inhibitors, morphologic characteristics, enzyme production, and their effect on the growth of Pinus taeda were studied. The actinobacteria were tested for their antagonistic capacity against Fusarium sp. in Petri plates with PDA as substrate. The inhibition zone was measured after 3, 5, 7, and 10 days. Of all the isolates tested, only two of them maintained inhibition zones up to 4 mm for 10 days. The inhibition of Armillaria sp. was tested in liquid medium and also in Petri dishes through the evaluation of the number of the fungal rhizomorphs in dual culture with the actinobacteria. It was found that all five isolates were able to inhibit the rhizomorph production, with the best performance of the isolate A43, which was capable of inhibiting both fungi, Fusarium and Armillaria. In a greenhouse experiment, the effect of five isolates on the growth of Pinus taeda seedlings was tested. Plant height, stem diameter, root and shoot dry matter were determined. The Streptomyces isolate A43 doubled plant growth. These results may lead to the development of new technologies in the identification of still unknown bacterial metabolites and new management techniques to control forest plant diseases.     

<Emphasis Type="Italic">In vitro</Emphasis> organogenesis of <Emphasis Type="Italic">Passiflora alata</Emphasis>

Passiflora alata in vitro organogenesis was studied based on explant type, culture medium composition, and incubation conditions. The results indicated that the morphogenic process occurred more efficiently when hypocotyl segment-derived explants were cultured in media supplemented with cytokinin and AgNO₃ incubated under a 16-h photoperiod. The shoot bud elongation and plant development were obtained by transferring the material to MSM culture medium supplemented with GA₃ and incubated in flasks with vented lids. Histological analyses of the process revealed that the difficulties in obtaining plants could be related to the development of protuberances and leaf primordia structures, which did not contain shoot apical meristem. Roots developed easily by transferring elongated shoots to 1/2 MSM culture medium. Plant acclimatization occurred successfully, and somaclonal variation was not visually detected. The efficiency of this organogenesis protocol will be evaluated for genetic transformation of this species to obtain transgenic plants expressing genes that can influence the resistance to Cowpea aphid borne mosaic virus.     

<Emphasis Type="Italic">In vitro</Emphasis> regeneration of <Emphasis Type="Italic">Salvia nemorosa</Emphasis> L. from shoot tips and leaf explants

Summary Shoot tips and leaves excised from in vitro shoot cultures of Salvia nemorosa were evaluated for their organogenic capacity under in vitro conditions. The best shoot proliferation from shoot tips was obtained on Murashige and Skoog (MS) medium supplemented with 8.9 μM 6-benzylaminopurine (BA) and 2.9 μM indole-3-acetic acid (IAA). Leaf lamina and petiole explants formed shoots through organogenesis via callus stage and/or directly from explant tissue. The highest values for shoot regeneration were obtained with 0.9 μM BA and 2.9 μM IAA for lamina explants. No shoot organogenesis was obtained on leaf explants cultured on MS medium supplemented with α-naphthaleneacetic acid (NAA). The regenerated shoots rooted the best on MS medium containing 0.6 μM IAA or 0.5 μM NAA. In vitro-propagated plants were transferred to soil with a survival rate of 85% after 3 mo.     

Regulation of the <Emphasis Type="Italic">ALBINO3</Emphasis>-mediated transition to flowering in <Emphasis Type="Italic">Arabidopsis</Emphasis> depends on the expression of <Emphasis Type="Italic">CO</Emphasis> and <Emphasis Type="Italic">GA1</Emphasis>

ALBINO3, a homologue of PPF1 in Arabidopsis, encodes a chloroplast protein, and is essential for chloroplast differentiation. In the present study, ALBINO3(−) transgenic plants exhibited a significant decrease in both the number of rosette leaves at bolting and the days before bolting, suggesting the important roles of ALBINO3 in regulating flowering during non-inductive short-day photoperiods. ALBINO3 mRNA was apparently accumulated in shoot apical meristem and floral meristems around the shoot apical meristem in wild-type plants. ALBINO3 might be predominantly involved in inducing the floral repression pathway by activating the expression of TFL1, and by suppressing the expression of LFY, respectively, in the shoot apical meristem. Moreover, the function of ALBINO3 in regulating flowering transition depended on the expression of CO and GA1, because ALBINO3 might function in the downstream integration of the photoperiod-dependent and the photoperiod-independent pathways. These results suggest that ALBINO3 may have an important integrative function in the flowering process in Arabidopsis.     

Pathway and sink activity for photosynthate translocation in <Emphasis Type="Italic">Pisolithus</Emphasis> extraradical mycelium of ectomycorrhizal <Emphasis Type="Italic">Pinus thunbergii</Emphasis> seedlings

The purpose of this study was to identify the pathway and sink activity of photosynthate translocation in the extraradical mycelium (ERM) of a Pisolithus isolate. We labelled ectomycorrhizal (ECM) Pinus thunbergii seedlings with ¹⁴CO₂ and followed ¹⁴C distribution within the ERM by autoradiography. ¹⁴C photosynthate translocation in the ERM resulted in ¹⁴C distribution in rhizomorphs throughout the ERM, with ¹⁴C accumulation at the front. When most radial mycelial connections between ECM root tips and the ERM front were cut, the whole allocation of ¹⁴C photosynthates to the ERM was reduced. However, the overall pattern of ¹⁴C distribution in the ERM was maintained even in regions immediately above and below the cut, with no local ¹⁴C depletion or accumulation. We inferred from this result that every portion in the ERM has a significant sink activity and a definite sink capacity for photosynthates and that photosynthates detour the cut and reach throughout the ERM by translocation in every direction. Next, we prepared paired ECM seedlings, ERMs of which had been connected with each other by hyphal fusion, alongside, labelled the left seedling with ¹⁴CO₂, and shaded none, one or both of them. ¹⁴C photosynthates were acropetally and basipetally translocated from the left ERM to ECM root tips of the right seedling through rhizomorphs in the left and right ERMs, respectively. With the left seedling illuminated, ¹⁴C translocation from the left to the right ERM increased by shading the right seedling. This result suggests that reduced photosynthate transfer from the host to its ERM increased sink activity of the ERM.