Carbon input by roots into the soil: Quantification of rhizodeposition from root to ecosystem scale

Despite its fundamental role for carbon (C) and nutrient cycling, rhizodeposition remains ‘the hidden half of the hidden half’: it is highly dynamic and rhizodeposits are rapidly incorporated into microorganisms, soil organic matter, and decomposed to CO₂. Therefore, rhizodeposition is rarely quantified and remains the most uncertain part of the soil C cycle and of C fluxes in terrestrial ecosystems. This review synthesizes and generalizes the literature on C inputs by rhizodeposition under crops and grasslands (281 data sets). The allocation dynamics of assimilated C (after ¹³C‐CO₂ or ¹⁴C‐CO₂ labeling of plants) were quantified within shoots, shoot respiration, roots, net rhizodeposition (i.e., C remaining in soil for longer periods), root‐derived CO₂, and microorganisms. Partitioning of C pools and fluxes were used to extrapolate belowground C inputs via rhizodeposition to ecosystem level. Allocation from shoots to roots reaches a maximum within the first day after C assimilation. Annual crops retained more C (45% of assimilated ¹³C or ¹⁴C) in shoots than grasses (34%), mainly perennials, and allocated 1.5 times less C belowground. For crops, belowground C allocation was maximal during the first 1–2 months of growth and decreased very fast thereafter. For grasses, it peaked after 2–4 months and remained very high within the second year causing much longer allocation periods. Despite higher belowground C allocation by grasses (33%) than crops (21%), its distribution between various belowground pools remains very similar. Hence, the total C allocated belowground depends on the plant species, but its further fate is species independent. This review demonstrates that C partitioning can be used in various approaches, e.g., root sampling, CO₂ flux measurements, to assess rhizodeposits’ pools and fluxes at pot, plot, field and ecosystem scale and so, to close the most uncertain gap of the terrestrial C cycle.     

Regeneration of Lycium barbarum L. plants from leaf tissue,callus culture and callus protoplasts

The possibility of plant regeneration from leaf tissue, callus and callus protoplasts of Lycium barbarum L. has been studied. Leaf segments were cultured on B5 medium (Gamborg et al. 1968) containing 1.5 mg/1 6-benzylaminopurine and 0.5 mg/1 -naphthaleneacetic acid. Regeneration of shoots was initiated after 30 days of cultivation. Callus was obtained from leaf and internode tissues on MS medium (Murashige and Skoog 1962) containing 0.4 mg/1 of 2,4dichlorophenoxyacetic acid. Subsequently, callus was successfully subcultured on the same medium with 1 mg/l of 2,4-dichlorophenoxyacetic acid and 0.2 mg/l -naphthaleneacetic acid. Organogenesis in callus culture was obtained in the course of 40 days after transferring to TM-4 (Shahin 1984). Protoplasts were isolated from callus tissue grown in vitro using an enzymatic method. Cell colonies, minicallus formation and organogenesis were obtained. Shoots were rooted on Murashige and Skoog medium containing 0..1 mg/l -naphthaleneacetic acid. Regenerated plants were transferred to soil and were grown to maturity. Regenerated plants carried normal morphological traits.Abbreviations BA 6-benzylaminopurine - 2,4-D 2,4-dichlorophenoxyacetic acid - NAA -naphthaleneacetic acid - Zea zeatin - GA₃ gibberellic acid - MS Murashige and Skoog medium - B5 Gamborg medium     

The ultrastructural immunocytochemical localization of superoxide dismutase in the amphibian urinary bladder: Effect of aldosterone

Summary Transmission electron microscopy and immunohistochemistry, the latter employing the avidin—biotin—peroxidase (ABC complex) technique, were utilized to localize copper—zinc superoxide dismutase (CuZn—SOD) enzyme activity in the epithelial cells of the toad urinary bladder mucosa. This scavenger enzyme catalyses the dismutation (reduction—oxidation) of the superoxide anion (O₂ ^–), a toxic free radical generated during normal cellular respiration. In unstimulated epithelial cells, enzyme activity was seen in the cytosol of granular, mitochondrial-rich and goblet cells. The basal cells were generally devoid of enzyme activity. In addition to the cytosol, SOD activity was also seen in association with the apical plasma membrane of the epithelial cells. In the presence of the steroid hormone aldosterone (10^–7 m, 30 min—6 h), CuZn—SOD activity was markedly increased along the luminal mucosal membrane of granular, mitochondrial-rich and goblet cells. This increase was seen as early as 30 min after the addition of hormone, and as long as 6 h after treatment. The cytosolic reaction was usually decreased or absent under these conditions. From the data presented, it appears that CuZn—SOD is involved in electrolyte (sodium) transport in the epithelial cells of the toad urinary bladder. The latter may involve hormone-induced alterations in luminal cell membrane structure and chemistry.To whom reprint requests should be addressed.     

Carboxymethylated beta-1,3-glucan inhibits the binding and degradation of acetylated low density lipoproteins in macrophages In Vitro and modulates their plasma clearance In Vivo

In atherosclerotic lesions, macrophages are transformed into foam cells accumulating modified low density lipoproteins (LDL) via the scavenger receptor pathway. We have investigated the effects of carboxymethylated beta-1,3-glucan (CMG) on acetylated LDL (AcLDL) metabolism in murine peritoneal macrophages in vitro and upon the clearance of AcLDL by rat liver in vivo. In cultured murine peritoneal macrophages, CMG reduced substantially the AcLDL-induced synthesis of cholesteryl esters, decreased the binding and degradation of [¹²⁵I]-AcLDL in a dose-dependent manner with complete inhibition at 20–30 nM , but had no effect on the binding and degradation of native [¹²⁵I]–LDL. In contrast, other polysaccharides studied, namely zymosan, lipopolysaccharide, non-modified glucan and mannan Rhodexman, had a slight effect at concentrations significantly exceeding the concentrations of CMG. [¹²⁵I]-AcLDL injected intravenously into rats was cleared from the blood with a half-life of 3.7 min. About 56 per cent of the label of injected [¹²⁵I]-AcLDL was recovered in the liver 15 min after administration. Co-injection of the labelled AcLDL with CMG (25 mg kg^?1 b.w.) decreased the rate of AcLDL clearance so that the half-life increased to 6.0 min. Injections of CMG (25 mg kg^?1 b.w.) 48 and 24 h before the determination increased the rate of [¹²⁵I]-AcLDL clearance (with a half-life of about 2.3 min) and increased the uptake of AcLDL by the liver. We suggest that CMG competed with AcLDL for scavenger receptors in vitro and in vivo and repeated CMG injections before the measurements of AcLDL resulted in the induction of scavenger receptor function.     

Effects of salinity,N-nutrition and humidity on photosynthesis and protein metabolism ofChloris gayana Kunth

Summary Under high atmospheric humidity, Rhodes grass plants responded favourably to an increase in nitrate fertilization. Under low atmospheric humidity an optimum point was reached at lower N-treatment.Plants' growth was improved by a salinity treatment of up to 100 mM, at high atmospheric humidity. A higher salt concentration cancelled the favourable effect of added nitrate.The rise in yield which follows salt or nitrate treatments is apparently combined with an increase in activity of the key photosynthetic enzymes, Phosphoenol pyruvate carboxylase and Ribulose biphosphate carboxylase. A similar rise in activity is seen in nitrate reductase, a key enzyme in nitrogen metabolism. Evidently, all three enzymatic systems are not damaged in high salt treatments, and the potential photosynthetic capacity remained practically uneffected in all treatments. As no correlation could be found between transpiration and growth curves, it is assumed that the supply of CO₂ is also unhampered. Thus, the major negative effect of salinity, seems to be on protein synthesis, which eventually leads to disturbed growth.Agricultural Research Organization. The Volcanic Center.     

Tracheotomy: a method for transplantation of stem cells to the lung

Lung disease is a leading cause of death and likely to become an epidemic given increases in pollution and smoking worldwide. Advances in stem cell therapy may alleviate many of the symptoms associated with lung disease and induce alveolar repair in adults. Concurrent with the ongoing search for stem cells applicable for human treatment, precise delivery and homing (to the site of disease) must be reassured for successful therapy. Here, I report that stem cells can safely be instilled via the trachea opening a non-stop route to the lung. This method involves a skin incision, caudal insertion of a cannula into and along the tracheal lumen, and injection of a stem cell vehicle mixture into airways of the lung. A broad range of media solutions and stabilizers can be instilled via tracheotomy, resulting in the ability to deliver a wider range of cell types. With alveolar epithelium confining these cells to the lumen, lung expansion and negative pressure during inhalation may also assist in stem cell integration. Tracheal delivery of stem cells, with a quick uptake and the ability to handle a large range of treatments, could accelerate the development of cell-based therapies, opening new avenues for treatment of lung disease.     

Neoliberalism reified: suzhi discourse and tropes of neoliberalism in the People's Republic of China

Since the mid-1990s, 'neoliberalism' has grown in importance as an explanatory trope for socio-cultural anthropologists. This article seeks to unravel the various strands of neoliberalism's anthropological meaning and demonstrate the blind spots of using neoliberalism as an overarching trope. I begin by analysing the contradictions between two common forms of theorizing neoliberalism. The remainder of the article then focuses the initial discussion by examining a particular case: suzhi discourse in the People's Republic of China (PRC). Suzhi may be glossed as human quality, and suzhi discourse refers to the myriad ways in which this notion of human quality is used in processes of governing contemporary China. I discuss the strengths and weaknesses of the arguments of those who explain suzhi discourse in terms of neoliberalism and suggest ways in which this discourse might be contextualized more fruitfully than as a form of neoliberalism.