Uptake of phosphorus-32 by vesicular-arbuscular mycorrhizae
01 Jun 1969-Plant and Soil (Martinus Nijhoff, The Hague/Kluwer Academic Publishers)-Vol. 30, Iss: 3, pp 415-422
TL;DR: A fungitoxicant (parachloronitrobenzene) reduced phosphorus accumulation by mycorrhizae but did not significantly affect phosphate accumulation by nonmyCorrhizal roots.
Abstract: The uptake and accumulation of phosphorus by mycorrhizal and nonmycorrhizal onion plants were compared. The results of the experiments indicate:
1.
Mycorrhizal onion plants accumulated significantly more phosphorus in the roots and tops than nonmycorrhizal plants.
2.
Vesicular-arbuscular mycorrhizae are sites of increased phosphorus accumulation compared to nonmycorrhizal roots.
3.
A fungitoxicant (parachloronitrobenzene) reduced phosphate accumulation by mycorrhizae but did not significantly affect phosphate accumulation by nonmycorrhizal roots.
Citations
More filters
TL;DR: The content of 32P and 15N in the external hyphae at the various distances from the RC confirmed that hyphal transport of P and N was directed towards the host plant.
Abstract: SUMMARY
Subterranean clover (Trifolium subterraneum L. cv. Nuba) was grown alone or in symbiosis with Glomus intraradices Schenck and Smith in containers divided by a fine nylon mesh into a root compartment (RC) and a root-free hyphal compartment (HC). Extraradical hyphae spread into the HC where 32P and 15NH4+ were applied at 2 or 5 cm distance from the RC, when the plants were 42 d old. The time-course of hyphal transport of the tracers was followed by measuring the content of 32P and 18N in leaflets sampled at various times during a 30 d labelling period.
Plants colonized by G. intraradices had accumulated more of the applied tracers than the non-mycorrhizal controls at the end of the experiment and hyphal transport of both P and N could be demonstrated. The levels of 32P in the leaflets of mycorrhizal plants already exceeded those of non-mycorrhizal plants after 3 and 4-5 d with the tracers applied at 2 and 5 cm distance from the RC, respectively. Leaflets of non-mycorrhizal controls contained only traces of 32P, but considerable amounts of 15N, and mycorrhizas increased the concentration of 15N-labelled N in leaflets only with tracers applied at 5 cm distance from the RC. The total recovery of applied 15N was 70 % higher in mycorrhizal than in non-mycorrhizal plants when tracers were applied at 2 cm distance from the RC. When the distance from the RC and the tracers was increased to 5 cm, the total recovery of applied loN was 175% higher in mycorrhizal than in non-mycorrhizal plants. The content of 32P and 15N in the external hyphae at the various distances from the RC confirmed that hyphal transport of P and N was directed towards the host plant.
772 citations
TL;DR: Data show clearly that different endophytes vary enormously in their symbiotic effectiveness at different soil pHs, even where they did not enhance plant growth in studies of this nature.
Abstract: Summary
Nine vesicular-arbuscular mycorrhizal endophytes were assessed for their infectivity and ability to improve the growth of alpine strawberry seedlings in sterilized, low-phosphate soils (4 and 8 mg kg−1 NaHCO3-soluble P), limed to different pHs. At pH 4, Glomus clarum greatly stimulated plant growth, but the other endophytes except Gigaspora margarita and Glomus fasciculatum‘E3’ had little or no effect. The most efficient endophytes at pH 5 were E3, Acaulospora laevis and G. clarum. The largest plants were those growing at pH 7 and inoculated with Glomus epigaeum; A. laevis and G. clarum were ineffective at this pH. The most effective endophytes at pH 6 and 7 were G. epigaeum, Glomus mosseae, E3, Glomus caledonium and Gigaspora heterogama, although results varied slightly between soils. Most endophytes infected well at all pHs, even where they did not enhance plant growth. In studies of this nature plant growth is affected by different pHs, soil P levels and the inoculum used. Nevertheless these data show clearly that different endophytes vary enormously in their symbiotic effectiveness at different soil pHs. The practical implications of these results are discussed.
723 citations
TL;DR: AM colonisation can result in complete inactivation of the direct P uptake pathway via root hairs and epidermis; calculations of AM contributions to P uptake from total plant P will often be highly inaccurate; and lack of plant responsiveness does not mean that an AM fungus makes no contribution toP uptake.
Abstract: Summary
• We investigated structural and functional diversity in arbuscular mycorrhizal (AM) symbioses involving three plant species and three AM fungi and measured contributions of the fungi to P uptake using compartmented pots and 33P. The plant/fungus combinations varied in growth and P responses. Flax (Linum usitatissimum) responded positively to all fungi, and medic (Medicago truncatula) to Glomus caledonium and G. intraradices, but not Gigaspora rosea. Tomato (Lycopersicon esculentum) showed no positive responses.
• Hyphal growth in soil was very low for Gi. rosea and high for both Glomus spp. Hyphal lengths in root + hyphal compartment (RHC) and hyphal compartment (HC) were similar for G. intraradices, but much higher in HC for G. caledonium.
• Specific activities of 33P in plants and soil indicated that fungal P uptake made substantial contributions to five plant/fungus combinations and significant contributions to a further two. G. intraradices delivered close to 100% of the P in all three plants. G. caledonium and Gi. rosea delivered less P. The amount was not related to colonisation or to growth or P responses.
• We conclude that: AM colonisation can result in complete inactivation of the direct P uptake pathway via root hairs and epidermis; calculations of AM contributions to P uptake from total plant P will often be highly inaccurate; and lack of plant responsiveness does not mean that an AM fungus makes no contribution to P uptake.
611 citations
TL;DR: This chapter elaborates the microbially mediated increases in plant-available phosphorus (P) under soil conditions, one of the most important being the activity of the PS microbial population already in the soil.
Abstract: Publisher Summary This chapter elaborates the microbially mediated increases in plant-available phosphorus (P). The importance of microorganisms in soil nutrient cycling and their role in plant nutrition has been realized for a long time. Their active part in the decomposition and mineralization of organic matter and release of nutrients is crucial to sustaining the plant productivity. The concentration of total P in soils ranges from 0.02 to 0.5% and averages approximately 0.05%, the variation being largely because of differences in weathering intensity and parent material composition. The uptake of P from relatively insoluble sources can be affected by the type of plant growing in the soil. The effect of mycorrhizae on plant P uptake and the effect of soil P on mycorrhizae were among the first aspects of these symbioses studied. Under soil conditions, potential benefits of adding P-solubilizing (PS) organisms would depend on several factors, one of the most important being the activity of the PS microbial population already in the soil. In almost all cases, the major sources of PS isolates have been soils. The mechanism of action of PS microorganisms is also elaborated.
596 citations
TL;DR: The enhanced growth of plants infected by vesicular–arbuscular (VA) mycorrhizal fungi results primarily from improved uptake of soil phosphate.
Abstract: The enhanced growth of plants infected by vesicular–arbuscular (VA) mycorrhizal fungi results primarily from improved uptake of soil phosphate. Extra phosphate reaches the root through the fungal h...
419 citations
References
More filters
TL;DR: When plants previously growing under favourable temperature conditions were exposed for three days to a lower temperature, there was a several times higher exudation from the roots of maize and a marked rise from roots of cucumber in comparison with control plants.
Abstract: The composition of the root exudates of barley and wheat in the initial growth phases was investigated; amino acids, organic acids, sugars and certain aromatic compounds could be identified. A knowledge of the composition of root exudates is important from the standpoint of the interaction between the plants and the micro-organisms in the rhizosphere. Some aspects of the rhizosphere effect connected with the present work are discussed.
314 citations
TL;DR: The extent of the stimulus obtained depended on nutrient conditions and the subsequent level of infection developed in the root system, and marked stimulation occurred with low phosphate availability and high root infection.
Abstract: Summary
The growth effects of three mycorrhizal Endogone endophytes on tobacco, tomato and maize were examined. The extent of the stimulus obtained depended on nutrient conditions and the subsequent level of infection developed in the root system. Marked stimulation occurred with low phosphate availability and high root infection.
295 citations
TL;DR: The zone of solution of apatite surrounding colonies on agar plates was usually characteristic of organisms producing acid in liquid culture; however, the degree of solubilization was not proportional to the fall in pH.
Abstract: A number of microorganisms capable of solubilizing apatite mere isolated from soil and from the rhizosphere of plants Many genera of common soil fungi and bacteria were represented The organis~ns solubilizing apatite were consistently present in higher proportions in rhizosphere isolates than in those from nearby soil The zone of solution of apatite surrounding colonies on agar plates was usually characteristic of organisms producing acid in liquid culture; however, the degree of solubilization was not proportional to the fall in pH On subculturing, many isolates rapidly and irreversibly lost their ability to dissolve apatite Soil isolates lost their ability to solubilize apatite more readily than isolates from the rhizosphere
246 citations
TL;DR: There is as yet no positive proof of the solvent action of carbonic acid, excreted by the roots, upon soil minerals, and no definite conclusions can be drawn with regard to the influence of microorganisms on the phosphate intake by the plant under natural conditions.
Abstract: Introduction. The way in which insoluble phosphates are absorbed by the plant is still a matter of some doubt. I t is generally accepted tha t the carbonic acid, excreted by the plant roots, is capable of bringing insoluble phosphates into solution. This conception ultimately rests upon the classic experiments of L i e b i g 1) and S a c h s 2), who demonstrated that polished plates of marble and ostheolite were etched by the roots of different plants. According to M i 1 1 e r a), however, there is as yet no positive proof of the solvent action of carbonic acid, excreted by the roots, upon soil minerals. S t o k 1 a s a c.s. 4) made an extensive study of the microbiological solubilization of insoluble phosphates; in the majori ty of their experiments, however, they added to the soil 2,5 °/o glucose, which is oxidized to organic acids by different soil microbes. Besides which no comparision was made with sterile cultures, nor were any phosphate determinations made on the plant material. Consequently no definite conclusions can be drawn with regard to the influence of microorganisms on the phosphate intake by the plant under natural conditions. F r e d and H a a s 5) were the first to show that the etching of marble by the roots of peas was markedly increased in the presence of bacteria. They concluded that the etching was in no case caused by root excretions alone, CO 2 included, but that microbes in the rhizosphere played a very important r61e in this phenomenon. S t a r k e y 6) and G r ~i f 7) showed that the number of bacteria in the rhizosphere was far greater than the number at some distance
220 citations
TL;DR: Bacterial isolates from the roots of wheat (rhizoplane) were more active in oxidizing glucose and alanine than cultures isolated from rhizosphere and non-rhizosphcre soils.
Abstract: Bacterial isolates from the roots of wheat (rhizoplane) were more active in oxidizing glucose and alanine than cultures isolated from rhizosphere and non-rhizosphcre soils. In general, metabolic ac...
199 citations