Vascular Sheath Cells Research Articles

Morfoanatomi Hoya coronaria Berbunga Kuning pada Perlakuan Intensitas Cahaya Berbeda

Knowledge on the anatomical structure of Hoya coronaria Blume can help to understand the various function of the plant to support the success of Hoya cultivation outside its natural habitat. This study aims to examine the effect of differences in light intensity on the anatomical characteristics of yellow-flowered H. coronaria to evaluate the adaptation of H. coronaria outside its natural habitat. The experiment used a one-factor factorial completely randomized design with two light intensity treatments (highest daily light intensity 15 Klux) and no shade with the highest daily light intensity average 59 Klux). The preparation of the leaf paradermal incision was made using the whole preparation method while the transverse incision was made using the paraffin method. Based on the analysis of the anatomical structure of the leaves, H. coronaria is a plant with C3 photosynthesis type. Leaf anatomy is composed of a thick cuticle layer, a single layer of the epidermis, mesophyll tissue which is differentiated into palisade and sponges, has a wide intercellular air cavity, and there is a transport network with undeveloped vascular sheath cells. H. coronaria growing under higher light intensity had thicker upper and lower cuticle, lower epidermis, mesophyll layer, and spongy layer compared to lower light intensity. The chlorophyll content was not significantly different between those grown at low and high light intensities. Based on these results, it can be concluded that H. coronaria adapted to high light intensity (without shade) or locations exposed to direct sunlight.

Different physiological responses of C3 and C4 plants to nanomaterials.

Several studies have previously reported that nanomaterial uptake and toxicity in plants are species dependent. However, the differences between photosynthetic pathways, C3 and C4, following nanomaterial exposure are poorly understood. In the current work, wheat and rice, two C3 pathway species are compared to amaranth and maize, which utilize the C4 photosynthetic mechanism. These plants were cultured in soils which were spiked with CuO, Ag, TiO2, MWCNT, and FLG nanomaterials. Overall, the C4 plant exhibited higher resilience to NM stress than C3 plants. In particular, significant differences were observed in chlorophyll contents with rice returning a 40.9-54.2% decrease compared to 3.5-15.1% for maize. Fv/Fm levels were significantly reduced by up to 51% in rice whereas no significant reductions were observed in amaranth and maize. Furthermore, NM uptake in the C3 species was greater than that in C4 plants, a trend that was also seen in metal concentration. TEM results showed that CuO NPs altered the chloroplast thylakoid structure in rice leaves and a large number of CuO NPs were observed in the vascular sheath cells. In contrast, there were no significant changes in the chloroplasts in the vascular sheath and no significant CuO NPs were found in maize leaves. This study was the first to systematically characterize the effect of metal and carbon-based nanomaterials in soil on C3 and C4 plants, providing a new perspective for understanding the impact of nanomaterials on plants.

Some like it hot: the physiological ecology of C4 plant evolution.

The evolution of C4 photosynthesis requires an intermediate phase where photorespiratory glycine produced in the mesophyll cells must flow to the vascular sheath cells for metabolism by glycine decarboxylase. This glycine flux concentrates photorespired CO2 within the sheath cells, allowing it to be efficiently refixed by sheath Rubisco. A modest C4 biochemical cycle is then upregulated, possibly to support the refixation of photorespired ammonia in sheath cells, with subsequent increases in C4 metabolism providing incremental benefits until an optimized C4 pathway is established. 'Why' C4 photosynthesis evolved is largely explained by ancestral C3 species exploiting photorespiratory CO2 to improve carbon gain and thus enhance fitness. While photorespiration depresses C3 performance, it produces a resource (photorespired CO2) that can be exploited to build an evolutionary bridge to C4 photosynthesis. 'Where' C4 evolved is indicated by the habitat of species branching near C3-to-C4 transitions on phylogenetic trees. Consistent with the photorespiratory bridge hypothesis, transitional species show that the large majority of > 60 C4 lineages arose in hot, dry, and/or saline regions where photorespiratory potential is high. 'When' C4 evolved has been clarified by molecular clock analyses using phylogenetic data, coupled with isotopic signatures from fossils. Nearly all C4 lineages arose after 25Ma when atmospheric CO2 levels had fallen to near current values. This reduction in CO2, coupled with persistent high temperature at low-to-mid-latitudes, met a precondition where photorespiration was elevated, thus facilitating the evolutionary selection pressure that led to C4 photosynthesis.

Re-creation of a Key Step in the Evolutionary Switch from C3 to C4 Leaf Anatomy

SummaryThe C4 photosynthetic pathway accounts for ∼25% of primary productivity on the planet despite being used by only 3% of species. Because C4 plants are higher yielding than C3 plants, efforts are underway to introduce the C4 pathway into the C3 crop rice. This is an ambitious endeavor; however, the C4 pathway evolved from C3 on multiple independent occasions over the last 30 million years, and steps along the trajectory are evident in extant species. One approach toward engineering C4 rice is to recapitulate this trajectory, one of the first steps of which was a change in leaf anatomy. The transition from C3 to so-called “proto-Kranz” anatomy requires an increase in organelle volume in sheath cells surrounding leaf veins. Here we induced chloroplast and mitochondrial development in rice vascular sheath cells through constitutive expression of maize GOLDEN2-LIKE genes. Increased organelle volume was accompanied by the accumulation of photosynthetic enzymes and by increased intercellular connections. This suite of traits reflects that seen in “proto-Kranz” species, and, as such, a key step toward engineering C4 rice has been achieved.

IDENTIFIKASI TANAMAN BERDASARKAN TIPE FOTOSINTESIS PADA BEBERAPA SPESIES ANGGOTA GENUS FICUS MELALUI PENGAMATAN ANATOMI DAUN

<em>Photosynthesis is the process of carbohydrate synthesis of inorganic materials in plants pigmented with the help of sunlight energy. Based on the type of photosynthetic plants are divided into three kinds, namely C3, C4 and CAM. More adaptive C3 plants under conditions of high atmospheric CO<sub>2</sub> content and do not have vascular sheath while the C4 plant more adaptive hot and dry areas, have a vascular sheath cells which are well developed and contain chloroplasts when observed anatomic structures. The purpose of this study was to identify plants by type of photosynthesis in Ficus callosa, F. elastica, F. benjamina, F. fistulosa, F. septica, F. rubiginosa and F. pisocarpa through leaf anatomical observations that cut transversely. The results showed that F. elastica and F. callosa have well-developed sheath cells surrounding the xylem and phloem, while F. benjamina, F. fistulosa, F. septica, F. rubiginosa and F. Pisocarpa are not</em>

Extracellular ice and cell shape in frost-stressed cereal leaves: A low-temperature scanning-electron-microscopy study

Low-temperature scanning electron microscopy was used to examine transverse fracture faces through cereal leaf pieces subjected to frost. Specimens were studied before and after sublimation of the ice. The position of extracellular ice in the leaf was inferred from the difference between the specimen before and after sublimation and from ridges and points which occurred in the extracellular ice during sublimation. Steps in the fracture surface indicated that the fracture plane passed through the extracellular ice crystals as well as through cells and also helped identify extracellular ice. The cells in controls were turgid and extracellular ice was absent. Leaf pieces from hardened rye were excised and frost-stressed to-3.3°,-21° and-72°C, cooling at 2-12°·h(-1). Cell collapse and extracellular ice were evident at-3.3°C and increased considerably by-21° C. At-21° and-72°C the leaf pieces were mainly filled with extracellular ice and there were few remaining gas spaces. The epidermal and mesophyll cells were laterally flattened, perpendicular to their attachment to adjacent cells, and phloem and vascular sheath cells were more irregularly deformed. Leaf pieces from tender barley were cooled at 2°C·min(-1) to-20° C; they were then mainly filled with extracellular ice, and the cells were highly collapsed as in the rye. In rye leaves frozen to-3.6° C before excision, ice crystals occurred in peri-vascular, sub-epidermal and intervening mesophyll spaces. In rye leaf pieces frozen to-3.3° C after excision or to-3.6° C before excision, mesophyll cells were partly collapsed even when not covered by ice, indicating that collapse of the cell wall, as well as the enclosed protoplast, was driven by dehydration. No gas or ice-filled spaces were found between wall and the enclosed protoplast. It is suggested that this can be explained without invoking chemical bonding between cell wall and plasma membrane: when the wall pores are filled by water, the pore size would reduce vapour pressure so making penetration of the wall by ice or gas less likely.