Contrasting biomass allocations explain adaptations to cold and drought in the world's highest-growing angiosperms

BACKGROUND AND AIMS

Understanding biomass allocation among plant organs is crucial for comprehending plant growth optimization, survival and responses to global change drivers. Yet, mechanisms governing mass allocation in vascular plants from extreme elevations exposed to cold and drought stresses remain poorly understood.

METHODOLOGY

We analyzed organ mass weights and fractions in 258 Himalayan herbaceous species across diverse habitats (wetland, steppe, alpine), growth forms (annual, perennial taprooted, rhizomatous, cushiony), and climatic gradients (3500-6150 m elevation) to explore whether biomass distribution adhered to fixed allometric or optimal partitioning rules, and how variation in size, phylogeny, and ecological preferences influence their strategies for resource allocation.

KEY FINDINGS

Following the optimal partitioning theory, Himalayan plants distribute more biomass to key organs vital for acquiring and preserving limited resources necessary for their growth and survival. Allocation strategies are mainly influenced by plant growth forms and habitat conditions, notably temperature, water availability, and evaporative demands. Alpine plants primarily invest in belowground stem bases for storage and regeneration, reducing aboveground stems while increasing leaf mass fraction to maximize carbon assimilation in their short growing season. Conversely, arid steppe plants prioritize deep roots over leaves to secure water and minimize transpiration. Wetland plants allocate resources to aboveground stems and belowground rhizomes, enabling them to resist competition and grazing in fertile environments.

CONCLUSIONS

Himalayan plants from extreme elevations optimize their allocation strategies to acquire scarce resources under specific conditions, efficiently investing carbon from supportive to acquisitive and protective functions with increasing cold and drought. Intraspecific variation and shared ancestry did not significantly alter Himalayan plants' biomass allocation strategies. Despite diverse evolutionary histories, plants from similar habitats have developed comparable phenotypic structures to adapt to their specific environments. This study offers new insights into plant adaptations in diverse Himalayan environments and underscores the importance of efficient resource allocation for survival and growth in challenging conditions.

Functionally distinct assembly of vascular plants colonizing alpine cushions suggests their vulnerability to climate change

BACKGROUND AND AIMS

Alpine cushion plants can initially facilitate other species during ecological succession, but later on can be negatively affected by their development, especially when beneficiaries possess traits allowing them to overrun their host. This can be reinforced by accelerated warming favouring competitively strong species over cold-adapted cushion specialists. However, little empirical research has addressed the trait-based mechanisms of these interactions. The ecological strategies of plants colonizing the cushion plant Thylacospermum caespitosum (Caryophyllaceae), a dominant pioneer of subnival zones, were studied in the Western Himalayas.

METHODS

To assess whether the cushion colonizers are phylogenetically and functionally distinct, 1668 vegetation samples were collected, both in open ground outside the cushions and inside their live and dead canopies, in two mountain ranges, Karakoram and Little Tibet. More than 50 plant traits related to growth, biomass allocation and resource acquisition were measured for target species, and the phylogenetic relationships of these species were studied [or determined].

KEY RESULTS

Species-based trait-environment analysis with phylogenetic correction showed that in both mountain ranges Thylacospermum colonizers are phylogenetically diverse but functionally similar and are functionally different from species preferring bare soil outside cushions. Successful colonizers are fast-growing, clonal graminoids and forbs, penetrating the cushion by rhizomes and stolons. They have higher root-to-shoot ratios, leaf nitrogen and phosphorus concentrations, and soil moisture and nutrient demands, sharing the syndrome of competitive species with broad elevation ranges typical of the late stages of primary succession. In contrast, the species from open ground have traits typical of stress-tolerant specialists from high and dry environments.

CONCLUSION

Species colonizing tight cushions of T. caespitosum are competitively strong graminoids and herbaceous perennials from alpine grasslands. Since climate change in the Himalayas favours these species, highly specialized subnival cushion plants may face intense competition and a greater risk of decline in the future.

The Root-Associated Microbial Community of the World's Highest Growing Vascular Plants

Upward migration of plants to barren subnival areas is occurring worldwide due to raising ambient temperatures and glacial recession. In summer 2012, the presence of six vascular plants, growing in a single patch, was recorded at an unprecedented elevation of 6150 m.a.s.l. close to the summit of Mount Shukule II in the Western Himalayas (Ladakh, India). Whilst showing multiple signs of stress, all plants have managed to establish stable growth and persist for several years. To learn about the role of microbes in the process of plant upward migration, we analysed the root-associated microbial community of the plants (three individuals from each) using microscopy and tagged amplicon sequencing. No mycorrhizae were found on the roots, implying they are of little importance to the establishment and early growth of the plants. However, all roots were associated with a complex bacterial community, with richness and diversity estimates similar or even higher than the surrounding bare soil. Both soil and root-associated communities were dominated by members of the orders Sphingomonadales and Sphingobacteriales, which are typical for hot desert soils, but were different from communities of temperate subnival soils and typical rhizosphere communities. Despite taxonomic similarity on the order level, the plants harboured a unique set of highly dominant operational taxonomic units which were not found in the bare soil. These bacteria have been likely transported with the dispersing seeds and became part of the root-associated community following germination. The results indicate that developing soils act not only as a source of inoculation to plant roots but also possibly as a sink for plant-associated bacteria.

Vegetation dynamics at the upper elevational limit of vascular plants in Himalaya

A rapid warming in Himalayas is predicted to increase plant upper distributional limits, vegetation cover and abundance of species adapted to warmer climate. We explored these predictions in NW Himalayas, by revisiting uppermost plant populations after ten years (2003-2013), detailed monitoring of vegetation changes in permanent plots (2009-2012), and age analysis of plants growing from 5500 to 6150 m. Plant traits and microclimate variables were recorded to explain observed vegetation changes. The elevation limits of several species shifted up to 6150 m, about 150 vertical meters above the limit of continuous plant distribution. The plant age analysis corroborated the hypothesis of warming-driven uphill migration. However, the impact of warming interacts with increasing precipitation and physical disturbance. The extreme summer snowfall event in 2010 is likely responsible for substantial decrease in plant cover in both alpine and subnival vegetation and compositional shift towards species preferring wetter habitats. Simultaneous increase in summer temperature and precipitation caused rapid snow melt and, coupled with frequent night frosts, generated multiple freeze-thaw cycles detrimental to subnival plants. Our results suggest that plant species responses to ongoing climate change will not be unidirectional upward range shifts but rather multi-dimensional, species-specific and spatially variable.

Plant diversity changes during the postglacial in East Asia: insights from Forest Refugia on Halla Volcano, Jeju Island

Understanding how past climate changes affected biodiversity is a key issue in contemporary ecology and conservation biology. These diversity changes are, however, difficult to reconstruct from paleoecological sources alone, because macrofossil and pollen records do not provide complete information about species assemblages. Ecologists therefore use information from modern analogues of past communities in order to get a better understanding of past diversity changes. Here we compare plant diversity, species traits and environment between late-glacial Abies, early-Holocene Quercus, and mid-Holocene warm-temperate Carpinus forest refugia on Jeju Island, Korea in order to provide insights into postglacial changes associated with their replacement. Based on detailed study of relict communities, we propose that the late-glacial open-canopy conifer forests in southern part of Korean Peninsula were rich in vascular plants, in particular of heliophilous herbs, whose dramatic decline was caused by the early Holocene invasion of dwarf bamboo into the understory of Quercus forests, followed by mid-Holocene expansion of strongly shading trees such as maple and hornbeam. This diversity loss was partly compensated in the Carpinus forests by an increase in shade-tolerant evergreen trees, shrubs and lianas. However, the pool of these species is much smaller than that of light-demanding herbs, and hence the total species richness is lower, both locally and in the whole area of the Carpinus and Quercus forests. The strongly shading tree species dominating in the hornbeam forests have higher leaf tissue N and P concentrations and smaller leaf dry matter content, which enhances litter decomposition and nutrient cycling and in turn favored the selection of highly competitive species in the shrub layer. This further reduced available light and caused almost complete disappearance of understory herbs, including dwarf bamboo.

The changes in the endothelial expression of cell adhesion molecules and iNOS in the vessel wall after the short-term administration of simvastatin in rabbit model of atherosclerosis

Cell adhesion molecules P-selectin, VCAM-1 and ICAM-1 play an important role in the pathogenesis of atherosclerosis. High levels of nitric oxide (NO) produced by inducible NO synthase (iNOS) have been associated with atherosclerotic processes. Simvastatin is an HMG-CoA reductase inhibitor responsible for many clinical benefits. The aim of this study was to detect and quantify changes in endothelial expression of P-selectin, VCAM-1, ICAM-1 and iNOS in the vessel wall after the short-term administration of simvastatin in a rabbit model of atherosclerosis. Eighteen New Zealand White rabbits were randomly divided into three groups (n = 6). In the cholesterol group, rabbits consumed an atherogenic diet (0.4% cholesterol) for eight weeks. In the simvastatin group, rabbits consumed an atherogenic diet for six weeks and then consumed an atherogenic diet supplemented with simvastatin (10 mg kg−1) for two weeks. Biochemical analysis showed that administration of simvastatin led to an almost two-fold lowering of the total serum cholesterol, VLDL, LDL and HDL, but not triglycerides, compared with the cholesterol-fed rabbits only. Stereological analysis of the immuno-histochemical staining revealed that administration of simvastatin (10 mg kg−1 daily) in an atherogenic diet decreased the endothelial expression of P-selectin, ICAM-1 and iNOS in both aortic arch and carotid artery compared with the cholesterol fed-rabbits only. We conclude that simvastatin has beneficial effects on endothelial function by decreasing expression of P-selectin, ICAM-1 and iNOS in endothelial cells in the very early stages of atherogenesis.

Changes in the expression of P-cadherin in the normal, cryptorchid and busulphan-treated rat testis

Adhesion between Sertoli cells and germ cells is important for spermatogenesis. Cadherins are Ca(2+)-dependent transmembrane proteins that mediate cell-cell adhesion. The aim of this study was to compare the expression of P-cadherin in unilaterally cryptorchid and busulphan-treated rat testes using immunohistochemistry. The pattern of expression of P-cadherin in the seminiferous epithelium changed with the stage of the seminiferous epithelium. The membranes of round spermatids and membranes and cytoplasm of spermatocytes were strongly positive. Our experiments revealed that busulphan treatment (2 doses - 10 mg/kg of body weight - 21 days apart) and cryptorchism led to destructive changes in the structure of seminiferous tubules, together with the decrease in P-cadherin expression. The expression of P-cadherin disappeared in the spermatids segregated from the epithelium while segregated spermatocytes remained still positive for P-cadherin during the 3- to 11-day cryptorchid period. In busulphan-treated animals, the expression of P-cadherin was dependent on the presence or absence of the spermatocytes and spermatids in the tubules. Strong positivity for P-cadherin was observed in the spermatocytes that re-appeared in the regenerating seminiferous epithelium. We suggest that P-cadherin participates in the architecture of adherens junctions in testis, plays an important role in maintaining normal spermatogenesis and that cryptorchism and busulphan treatment lead to adherens junction disintegration.

Biodistribution and elimination characteristics of two 111In-labeled CCK-2/gastrin receptor-specific peptides in rats

BACKGROUND

Due to their high CCK-2/gastrin receptor selectivity, high affinity, and rapid background clearance, radiolabeled minigastrins (MG) are emerging as promising new tools in the diagnosis and therapy of CCK-2/gastrin receptor-positive tumors. In this study, the pharmacokinetic profile, particularly the excretion mode, of two 111In-labeled minigastrins was compared in rats. The first tracer, 111In-MG-0 is based on (D)Glu1-MG, while the second, 111In-MG-11, is its des-(Glu)5-derivative, expected to be less retained in renal tissue.

MATERIALS AND METHODS

The fate of 111In-MG-0 and 111In-MG-11 in the body of rats was investigated during biodistribution and bioelimination experiments, while the respective elimination parameters were determined in perfused rat liver and kidney models.

RESULTS

During biodistribution both compounds were rapidly cleared from the blood and most non-target organs whereas activity levels in the bowel and stomach declined slowly. The overall contribution of hepatobiliary excretion of 111In-MG-0 and 111In-MG-11 was relatively small. In the perfused rat liver their elimination into the bile was negligible. In contrast, renal excretion was the major excretion pathway for both analogs, mainly via glomerular filtration. However, kidney levels were substantially higher and retention was more prolonged in the case of 111In-MG-0 as compared to 111In-MG-11.

CONCLUSION

The presence of the (Glu)5-chain in 111Ln-MG-0 appears to be implicated in the prolonged radioactivity retention in the kidney of rats.

MDOC™ and atorvastatin have potential antiinflammatory effects in vascular endothelium of apoE−/− mouse model of atherosclerosis

Members of the immunoglobulin superfamily of endothelial adhesion molecules, vascular cell adhesion molecule (VCAM-1) and intercellular cell adhesion molecule (ICAM- 1), strongly participate in leukocyte adhesion to the endothelium and play an important role in all stages of atherogenesis. The aim of this study was to detect and quantify the changes of endothelial expression of VCAM-1, and ICAM-1 in the vessel wall after the short-term administration of simvastatin, atorvastatin, and micro dispersed derivatives of oxidised cellulose (MDOC) in apolipoprotein-E-deficient (apoE(-/-)) mice atherosclerotic model. Hyperlipidemic apoE(-/-) mice (n = 32) received normal chow diet or diet containing simvastatin or atorvastatin 10 mg/kg/day or MDOC 50 mg/kg/day. Total cholesterol, VLDL, LDL, HDL and TAG were measured and the endothelial expression of VCAM-1 and ICAM-1 was visualized and quantified by means of immunohistochemistry and stereology, respectively. Total cholesterol levels was insignificantly lowered only in MDOC treated mice but not in mice treated with statins. ICAM-1 endothelial expression was not affected by neither simvastatin nor MDOC treatment. However, significant diminution of VCAM-1 endothelial expression was observed in both atorvastatin and MDOC treated mice. These results provide new information of potential hypolipidemic substance MDOC and its potential anti-inflammatory effects. Furthermore, we have confirmed anti-inflammatory effects of atorvastatin independent of plasma cholesterol lowering. Thus, the results of this study show potential benefit of both MDOC and atorvastatin treatment in apoE(-/-) mouse model of atherosclerosis suggesting their possible combination might be of interest.

Vimentin expression during altered spermatogenesis in rats

The collapse of vimentin caused by some xenobiotics correlates with the loss of structural integrity of the seminiferous epithelium. In this study, we investigated the effect of busulphan (an anticancer drug with toxic effects on dividing germ cells) on vimentin filament distribution in rat seminiferous epithelium and compared it with changes found in testes of unilaterally cryptorchid rats. In the seminiferous epithelium, the vimentin labelling was observed only in the Sertoli cells, showing a stage-specific arrangement of the filaments. Both busulphan treatment and cryptorchism caused altered distribution of vimentin filaments in the Sertoli cells. In both models, the apical vimentin filaments collapsed towards the nuclei and were disorganized in the basal region of the Sertoli cells while the germ cells were diminished in the epithelium. After the busulphan effect subsided (4 weeks after administration), spermatogenesis began to restore and vimentin filaments began to organize in basal and perinuclear regions of Sertoli cells among the spermatogonia and spermatocytes. Vimentin labelling of the sloughed material in the lumen of cryptorchid testes (but not in busulphan treated animals) was observed. We conclude that the Sertoli cell vimentin filaments play an important role in the maintenance of spermatogenesis, their damage is associated with the seminiferous epithelium disintegration and their restoration with a recovery of spermatogenesis after the unfavourable conditions subside.

99mTc demotate 1: biodistribution and elimination characteristics in rats

BACKGROUND AND METHODS

In this study, we investigated the biodistribution and elimination characteristics of a new radiolabelled somatostatin analogue, 99mTc demotate 1, in rats by in-vivo biodistribution and elimination experiments, perfused rat liver and kidney experiments and micro-autoradiography of renal tissue.

RESULTS

Rapid clearance from blood and most organs was found. High and long-term uptake in organs with high density of somatostatin receptors (the adrenals and pancreas) and in stomach and intestine was reduced in non-radiolabelled octreotide pretreated animals. The predominant urine excretion was associated with an accumulation of 99mTc demotate 1 in the kidney, mainly in the renal cortex. This uptake was not affected by non-radiolabelled octreotide pretreatment.

CONCLUSION

99mTc demotate 1 is a prospective radiopharmaceutical for use in human medicine in somatostatin receptor-positive tumour imaging and its potential should be confirmed in further experiments and clinical trials.

Analysis of accumulation of 99mTc-octreotide and 99mTc-EDDA/HYNIC-Tyr3-octreotide in the rat kidneys

The aim of this study was to compare renal handling and distribution of (99m)Tc-octreotide and (99m)Tc-EDDA/HYNIC-Tyr(3)-octreotide (HYNIC-TOC) in rats. In kidney perfusion experiments, the renal clearance value of (99m)Tc-octreotide was three times lower than that of (99m)Tc-EDDA/HYNIC-TOC. The predominant renal excretion of (99m)Tc-EDDA/HYNIC-TOC was associated with a high and long-term renal accumulation up to 48 hrs. Microautoradiographic results indicated that (99m)Tc-EDDA/HYNIC-TOC was retained mainly in the renal medulla within the cells of the collecting ducts and in the surrounding tissue. Lower positivity was found in the proximal and distal tubular cells. We conclude that the mechanism of renal accumulation of somatostatin analogues renal accumulation is complex and that proximal tubular reabsorption is probably not the main mechanism for uptake of (99m)Tc-EDDA/HYNIC-TOC in the kidneys. The presence of the somatostatin receptors, differences in the tonicity level within kidneys and other possible mechanisms could participate in their renal accumulation.

P-glycoprotein expression and distribution in the rat placenta during pregnancy

P-glycoprotein (P-gp) is a drug efflux transporter that limits the entry of various potentially toxic drugs and xenobiotics into the fetus and is thus considered a placental protective mechanism. In this study, P-gp expression was investigated in the rat chorioallantoic placenta over the course of pregnancy. Three methods have been employed: real-time RT-PCR, western blotting and immunohistochemistry. The expression of mdr1a and mdr1b genes was demonstrated as early as on the 11th gestation day (gd) and increased with advancing gestation. Western blotting analysis revealed the presence of P-gp in the rat placenta starting from gd 13 onwards. P-gp was localized in the developing labyrinth zone of the placenta on gd 13; from gd 15 up to the term P-gp was seen as a dot like continuous line in the syncytiotrophoblast layers. Our data confirm the presence of P-gp in the rat chorioallantoic placenta starting soon after its development, which may signify the involvement of P-gp in transplacental pharmacokinetics during the whole period of placental maturing.

Application of stereological methods for the quantification of VCAM-1 and ICAM-1 expression in early stages of rabbit atherogenesis

Early stages of atherogenesis are characterized by the overexpression of cell adhesion molecules with the subsequent accumulation of macrophages, smooth muscle cells and proliferation of extracellular matrix in arterial intima. The quantification of atherogenic changes is necessary for the objective evaluation of the atherogenic process. The purpose of this study was to introduce stereological methods that may be used for the quantification of immunohistochemical staining, namely intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Twenty-four New Zealand White rabbits were subdivided into the three groups. Eighteen rabbits received a 0.4% cholesterol diet for 1, 2 and 3 months, respectively. Stereological principles of the systematic uniform random sampling and the point-counting method were applied for the quantification. Stereological analysis showed that VCAM-1 and ICAM-1 were upregulated during the consumption of high cholesterol diet and that VCAM-1, but not ICAM-1, has a considerable role in the formation of early atherosclerotic lesions. Stereological methods proved to be useful for the quantification of immunohistochemistry and can be used for an objective characterization of atherogenic changes in atherosclerosis.

Examination of the functional activity of P-glycoprotein in the rat placental barrier using rhodamine 123

Rhodamine 123 (Rho123), a model substrate of P-glycoprotein (P-gp), was used to evaluate the functional activity of P-gp efflux transporter in the rat placental barrier. The dually perfused rat-term placenta method was used. In our experiments, the materno-fetal transplacental passage of Rho123 did not meet the criteria of the first-order pharmacokinetics, suggesting an involvement of transporter-mediated process. Inhibitors of P-gp, such as [3'-keto-Bmt1]-[Val2]-cyclosporine (PSC833), cyclosporine (CsA), quinidine, and chlorpromazine, increased significantly the materno-fetal transplacental passage of Rho123 in the experiments under steady-state conditions. On the other hand, PSC833, CsA, and quinidine decreased the feto-maternal passage of Rho123. Similarly, in the experiments carried out under nonsteady-state conditions, CsA accelerated the passage of Rho123 in the materno-fetal direction and decreased its passage in the opposite direction. Feto-maternal transplacental clearances of Rho123 were found to be considerably higher than those in the materno-fetal course. Potent P-gp inhibitors, such as PSC833 or CsA, partially canceled the asymmetry. Negligible metabolism of Rho123 into its major demethylated metabolite rhodamine 110 was observed in the rat placenta. Expression of P-gp genes was detected using immunohistochemical, Western blotting, and reverse transcription-polymerase chain reaction methods preferentially in the second rat syncytiotrophoblast layer. In conclusion, these data suggest that P-gp limits the entry of Rho123 into fetuses and at the same time it accelerates the feto-maternal elimination of the model compound. Therefore, it seems plausible that pharmacokinetics of xenobiotics in the rat placental barrier could be controlled by P-gp in both directions.

X-ray absorption holography

The transmission of monochromatic x rays through a CoO single crystal was measured for different orientations of the sample. The small variations in the linear absorption coefficient were considered as a hologram and the real-space image of the local atomic environment was successfully reconstructed. The holographic signal constituted about 1% of the detected intensity. Besides other benefits, the use of the absorption holography can increase the signal-to-background ratio by more than 1 order compared with the fluorescence holography.

[Psychosocial dwarfism]

A 4 year old girl with psychosocial dwarfism showed hepatomegaly, abdominal distension and behavioral disturbances. Laboratory tests revealed a reversible elevation of serum liver enzymes and a reversible partial growth hormone deficiency. The child's family was characterised by severe social problems and all signs of a depriving and child abusing environment. All pathologic findings were reversed by removing the child from her depriving family background. This case demonstrates that psychosocial dwarfism represents an aspect of child abuse (battered child syndrome).