Calcium carbonate deposition in a cell wall sac formed in mulberry idioblasts

Growing on calcareous soils and facing climate change

Soil calcium carbonate (CaCO3) impacts plant mineral nutrition far beyond Fe metabolism, imposing constraints for crop growth and quality in calcareous agrosystems. Our knowledge on plant strategies to tolerate CaCO3 effects mainly refers to Fe acquisition. This review provides an update on plant cellular and molecular mechanisms recently described to counteract the negative effects of CaCO3 in soils, as well as recent efforts to identify genetic bases involved in CaCO3 tolerance from natural populations, that could be exploited to breed CaCO3-tolerant crops. Finally, we review the impact of environmental factors (soil water content, air CO2, and temperature) affecting soil CaCO3 equilibrium and plant tolerance to calcareous soils, and we propose strategies for improvement in the context of climate change.

Effect of Graphene Oxide on the Crystallization of Calcium Carbonate by C3S Carbonation

The effect of graphene oxide (GO) on the crystallization of calcium carbonate (CaCO₃) is explored in this paper. Precipitation of CaCO₃ was carried out by bubbling carbon dioxide (CO₂) through tricalcium silicate (C₃S) hydration solution with different graphene oxide admixture contents (0.2%, 1% and 2% mass ratios based on C₃S). The polymorph, morphology, crystal size and particle size of CaCO₃ were evaluated using X-ray diffraction (XRD), an environmental scanning electronic microscope (ESEM), and laser particle size analysis. The results showed that addition of GO was able to promote the conversion of CaCO₃ to a calcite crystal phase with higher thermal stability and crystallinity than the control. However, as the dosage of GO increased, the growth of the calcite crystal particles was somewhat suppressed, resulting in a decrease in the crystal particle size and a narrow particle size distribution. When the amount of GO was 0.2%, 1% and 2%, the crystal size of the calcite was 5.49%, 12.38%, and 24.61% lower than that of the sample without GO, respectively, while the particle size of the calcite also decreased by 17.21%, 39.26%, 58.03%, respectively.

Physiological and ecological significance of biomineralization in plants

Biomineralization is widespread in the plant kingdom. The most common types of biominerals in plants are calcium oxalate crystals, calcium carbonate, and silica. Functions of biominerals may depend on their shape, size, abundance, placement, and chemical composition. In this review we highlight advances in understanding physiological and ecological significance of biomineralization in plants. We focus on the functions of biomineralization in regulating cytoplasmic free calcium levels, detoxifying aluminum and heavy metals, light gathering and scattering to optimize photosynthesis, aiding in pollen release, germination, and tube growth, the roles it plays in herbivore deterrence, biogeochemical cycling of carbon, calcium, and silicon, and sequestering atmospheric CO2.

Calcium and silicon mineralization in land plants: transport, structure and function

Plant biomineralization involves calcium and silicon transport and mineralization. Respective analytical methods and case studies are listed. Calcium carbonate is deposited in cystoliths, calcium oxalate in idioblasts. Silicon is deposited in phytoliths. Biomineralization is a coordinated process.

Localization of mucilaginous polysaccharides in mulberry leaves

Mulberry tree leaves were shown to have mucilaginous polysaccharides. The extracted water-soluble mucilage was separated into three fractions via a cetylpyridinum chloride complex and purified by anion-exchange chromatography. Five acidic polysaccharides were separated from these fractions, one of which was a major polysaccharide (Mp-3) that was structurally analyzed and used for antibody preparation. The Mp-3 polysaccharide contained rhamnose, galactose, glucose, galacturonic acid, and glucuronic acid in a molar ratio of 1 : 0.2 : 0.5 : 2.3 : 1.5 as constituent monosaccharides. Methylation and gas chromatography-mass spectrometry analysis indicated that the polysaccharide was a rhamnogalacturonan mainly consisting of 1,2,3-linked rhamnose residues, 1,3,4- and 1,4-linked uronic acid residues, and terminal uronic acid residues. Its molecular weight was estimated to be 5.5 x 10(5). Immunohistological observation revealed that the Mp-3 polysaccharide is specifically localized in inner epidermal cells situated in adaxial leaves, and electron microscopy showed that its subcellular location is between the plasma membrane and the cell wall. In young leaves, numerous secretory vesicles were present in a shrunken cytoplasm that was surrounded by fibers. In mature leaves, more than 20% of total epidermal cells were these inner cells in which polysaccharide deposition was significantly increased. The deposits appeared as a rounded electron-dense mass throughout the inner cells by electron microscopy.

Ultrastructural and immunochemical features of the cell wall sac formed in mulberry (Morus alba) idioblasts

A peculiar inward growth, named a "cell wall sac", formed in mulberry (Morus alba) idioblasts, is a subcellular site for production of calcium carbonate crystals. On the basis of ultrastructural observations, a fully expanded cell wall sac could be divided into two parts-an amorphous complex consisting of multi-layered compartments with multiple fibers originating from the innermost cell wall layer, and a peripheral plain matrix with fiber aggregates. Immunofluorescent localization showed that low and highly esterified pectin epitopes were detected at the early stages of development of the cell wall sac, followed by complete disappearance from the both parts of fully enlarged mature sac. In contrast, the xyloglucan epitope remained in the compartment complex; this was supported by the observation that the xyloglucan epitope labeled with immuno-gold particles is found on fibers in the complex part.

The future of stone research: rummagings in the attic, Randall's plaque, nanobacteria, and lessons from phylogeny

The prevention or cure of stone disease will be achieved only by identifying biochemical, physiological and molecular mechanisms operating before the formation of a calculus. Yet, the gradual increase in the total number of papers devoted to the study of kidney stones that has occurred since the beginning of the 21st century can be attributed almost entirely to papers concerned with the investigation of factors associated with urolithiasis after stones have already formed. The need to prevent stones by discovering how the human body routinely stops their formation in those of us who do not suffer from them is therefore as exigent as ever and a new approach to investigating the causes of stones is urgently needed. In this paper, I develop the view that stone research will best progress by examining and understanding how healthy plants and animals control the formation of biominerals. In addition to structures like bones, teeth, shells and spines, many organisms spanning the entire phylogenetic tree form intra- and extracellular granules which are use as storage depots for calcium and other important ions, which they can reclaim to maintain homeostasis or to satisfy specific needs during periods of high demand, such as shell formation, moulting or skeletal development. These electron-dense granules, which also bear an uncanny resemblance to calcified nanobacteria, are remarkably similar in general structure, size and composition to particles observed in healthy human kidneys and in Randall's plaque. Therefore, it is likely that the granules in human kidneys fulfil analogous functions to those in other organisms-particularly in calcium homeostasis. Their study in a large range of creatures has already provided a deep well of information about their structure, movement, composition, macromolecular content, synthesis and resorption, from which we can draw to quench our thirst for knowledge of basic mechanisms and events involved in the formation of human kidney stones.

Cell wall sheath surrounding calcium oxalate crystals in mulberry idioblasts

The distribution and ultrastructural features of idioblasts containing calcium oxalate crystals were studied in leaf tissues of mulberry, Morus alba L. In addition to the calcium carbonate crystals formed in epidermal idioblasts, large calcium oxalate crystals were deposited in cells adjacent to the veins and surrounded by a cell wall sheath which had immunoreactivity with an antibody recognizing a xyloglucan epitope. The wall sheath formation indicates exclusion of the mature crystal from the protoplast.

Cytological changes during cell wall sac formation in mulberry idioblasts

When calcium carbonate crystals are formed in mulberry (Morus abla) idioblasts, they are deposited in newly formed cell wall sacs. The initial cytological events leading to cell wall sac formation were observed in the distal end of young idioblasts and tentatively categorized into four stages. The first indication of formation was the separation of the innermost cell wall layer from the cell wall, which is followed by the deposition of egg-shaped polysaccharide on the inner cell wall surface. The size of the deposit area increased, while the thickness of the cell wall significantly decreased during the next stage. Finally, the condensed cellulosic lamella was invaginated into the deposition area, resulting in the formation of an elongated cell wall sac. The internal cell wall sac was composed of numerous fibers with different morphologies. Application of gelatin-methenamine-silver staining allowed us to observe the spatial distribution of cellulosic polysaccharides as electron-dense images.