Summary
1.Two studies using the stable-isotope 13 C have shown that large amounts of carbon can move between plants linked by arbuscular mycorrhizal fungi. Quantities comparable to the carbon cost of the symbiosis for an individual plant may be transferred. 2. We measured C transfer between linked plants of the grass Cynodon dactylon (C 4 , δ 13 C ≈ -14‰) and the herb Plantago lanceolata (C 3 , δ 13 C ~ -28‰). To test the hypothesis that the carbon transferred between plants remained in fungal structures at all times, plants were grown for two harvests; at the first harvest they were clipped to ground level, so that shoot re-growth required the transport of carbon from the roots. We also tested the influence of the direction of growth of the fungus, to determine whether C was transported out of or into a newly colonized root, and of growing plants in elevated CO 2 , to increase the availability of carbon compounds in the roots. 3. Large amounts of C were transferred between linked plants, more so into Plantago than into Cynodon roots. Transfer occurred whether root systems were separated by a 20 µm mesh, that excluded roots but not hyphae, or a 0·45 µm mesh, intended to act as a barrier to hyphae as well. We believe that the high root densities achieved in the experiment allowed hyphae to cross the finer mesh between the two dense root mats. 4. Clipping the plants did not result in any movement of C from roots to shoots, thus confirming the prediction that all C transferred remains in fungal structures. 5. The direction of growth of the fungus did not affect the direction of transfer, nor did the CO 2 concentration in which the plants were grown. 6. The amount of C transferred was a positive correlate of the frequency of vesicles in the roots but a negative correlate of the frequency of hyphae. If C were moving into developing colonization units, thus effectively giving the plant a 'free' symbiosis, the correlation with internal hyphae should be positive. The positive correlation with vesicles suggests that C is moving into fungal storage structures. 7. We propose a mycocentric view of the phenomenon of interplant C transfer, in which the fungal colonies within roots are seen as parts of an extended mycelium between which the fungus moves resources depending on the dynamics of its own growth. We do not believe that the transfer has an impact on plant C budgets or fitness, but that it may be a major element in the understanding of fungal C budgets.
A patient who presented with sickle retinopathy and hemoglobin electrophoresis results compatible with sickle cell trait was found, on further investigation, to be a compound heterozygote with hemoglobin S and hemoglobin New York disease. This recently reported form of sickle cell disease was not previously known to cause retinopathy and surprisingly was observed in a non-Asian individual. The ophthalmological findings, the laboratory diagnosis, and possible pathophysiology of this disorder are discussed. Persons diagnosed with sickle cell trait who present with symptoms of sickle cell disease may benefit from specific screening for this variant.
Narratives of substance use disorder recovery experience can provide useful qualitative conceptual categories and novel theories about the way in which recovery is experienced by individuals. This information can better inform definitions, concepts, and supports for recovery processes. The current study reviewed 30 written personal recovery biographies which were contained within student applications to the collegiate recovery program housed in the Center for Young Adult Addiction and Recovery at Kennesaw State University. Using grounded theory methodology, common benchmarks, or topographic recovery features were revealed involving the evolution of identity as an inter-negotiated process throughout the addiction and recovery biographies (Charmaz, 2008; Glaser & Strauss, 2017). From this, a six-stage theory model of recovery identity is formulated and explored. The biographies contained accounts from pre-substance use through the full embracement of a recovery identity. This model may help to serve recovery program managers to classify incoming individuals, identify and address needs, and facilitate innovative programming to meet such needs as they relate to the identity transformation process.
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