The final part of our introduction to plant physiology is an overview of the plant body. Figure 1. Monocots have some differences but we will deal with these as they arise. Refer to this figure as we outline some key points. The plant body is linear in structure and is composed of two parts: the root and the shoot. The shoot grows upward toward light and air while the root grows down into the soil seeking water and dissolved nutrient ions.
Plants cannot move to get the things they need and so they must literally be in two places at once, growing in opposite directions simultaneously to achieve this. The plant body is said to consist of three kinds of organs: the roots, the shoots, and the leaves. Don't try to compare the organs of plants with the definition of an organ in animals. It is futile. Plants are different. Roots anchor the plant in the soil, absorb water and mineral nutrients, and store materials safe from harsh weather and above-ground herbivores.
Leaves perform photosynthesis by absorbing light and carbon dioxide. Modified leaves are the parts of flowers and thus also participate in reproduction. Stems hold leaves up to the light, hold flowers and seeds up for reproduction, and transport materials between the roots and leaves.
Each plant organ is composed of three tissue systems , known as the dermal, vascular, and ground tissue systems. They are called tissue systems because each is composed of one or more plant tissues.
The dermal tissue system is the outer covering of cells that protects plants from desiccation and attack by pathogens, pests, and herbivores. It consists of epidermis tissue, which is composed of several different cell types that include:. In the shoot and much of the root, epidermal cells have a coating of waxes and other waterproof materials known as the cuticle.
Epidermal cells do not have chloroplasts and are not green. Stomates are the pores that open and close to control loss of water from and entry of carbon dioxide into leaves. The latter was validated by inoculating 2 weeks-old root systems of the hypernodulation soybean mutants [i. As soon as 10 days after inoculation, nodules emerged. Thirty days after inoculation, a large number of nodules were developing on the hypernodulating soybean roots [NOD Compared to these mutants, 4. Although, we found that the number of nodules per root system is lower in the aeroponic system grown plants compared to vermiculite grown plants i.
These data support that this technology is fully compatible with the analysis of the early and late stages of legume nodulation. We assume that additional experiments and tests using the aeroponic system would maximize the number of nodules per plant.
Another potential attractive application of the aeroponic system is the generation of composite plants i. To test this potential utilization of the aeroponic system, we inoculated soybean shoots with Agrobacterium rhizogenes carrying our transgene of interest in this case, a fusion between the cassava vein mosaic virus promoter and the UidA gene which encodes the beta-glucuronidase.
Ten days after bacteria inoculation, a callus was formed and roots started to emerge Figure 5A. In average, we observed seven transgenic roots emerging from each composite plant. Stereomicroscopic observations revealed that these roots carry an impressive number of transgenic root hair cells Figure 5C.
Soybean transgenic roots and root hairs generated in the ultrasound areoponic system; A transgenic roots emerging from the callus 10 days after Agrobacterium rhizogenes inoculation; B GUS -stained soybean root system, the black arrows point at the transgenic root and the white arrows point at the non-transgenic root; C GUS -stained transgenic root hair cells.
In this manuscript, we combined the use of an ultrasound aeroponic system with updated method to isolate root hair cells to maximize the potential of plant root hair cell as a single cell type model for systems biology.
This updated method has the following advantages: 1 enhance root hair cell density on the root system; 2 even and long-term treatment of the entire population of root hair cells to access the molecular response of the root hairs to various biotic and abiotic stresses. In addition to be well-suited to perform —omics analyses at the level of one single cell type, the ultrasound aeroponic system has been validated to study plant-bacteria interactions and to produce large quantities of easy accessible plant material allowing functional genomic studies.
Undoubtly, our updated method of generating large amount of pure root hair cells will promote the progress of deciphering the regulatory mechanism of plant cell biology including plant cell response to environmental stresses. Soybean seeds Glycine max [L. Seed were finally washed three times with sterile water before sowing on sterilized mixture of vermiculite and perlite ratio. Cultured for another 2 weeks in areoponic system, the seedlings were collected into liquid nitrogen for root hair isolation.
Quantitative real-time PCR reactions were performed as described by Libault et al. Cycle threshold Ct values were obtained based on amplicon fluorescence thresholds. According to Vandesompele et al. The fold change of the gene expression levels between root hair versus stripped root was calculated for each root hair specific gene. Three independent biological replicates were generated for each condition and Student t -tests with two tails and two samples equal variance were applied to display the significant differences of gene expression between root hair and stripped root samples.
As described by Libault et al. Two weeks-old soybean plants grown on pro-mix were used to generate composite plants. Soybean shoots were cut between the first true leaves and the first trifoliate leaf and placed into rock-wall cubes Fibrgro. After 1 week, instead to transfer the composite plants into vermiculite-perlite as described by Libault et al. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Brechenmacher, L. Establishment of a protein reference map for soybean root hair cells. Plant Physiol. Soybean metabolites regulated in root hairs in response to the symbiotic bacterium Bradyrhizobium japonicum.
Identification of soybean proteins from a single cell type: the root hair. Proteomics 12, — Broughton, W. Control of leghaemoglobin synthesis in snake beans. Bruex, A. A gene regulatory network for root epidermis cell differentiation in Arabidopsis. PLoS Genet. Bucher, M. Two genes encoding extensin-like proteins are predominantly expressed in tomato root hair cells.
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A simple method for gene expression and chromatin profiling of individual cell types within a tissue. Cell 18, — Franklin-Tong, V. Signaling and the modulation of pollen tube growth. Plant Cell 11, — Gage, D. Infection and invasion of roots by symbiotic, nitrogen-fixing Rhizobia during nodulation of temperate legumes. Ithal, N. Developmental transcript profiling of cyst nematode feeding cells in soybean roots. Plant Microbe Interact. Ito, S. Soil Sci.
Plant Nutr. CrossRef Full Text. Kathryn, M. How rhizobial symbionts invade plants: the Sinorhizobium—Medicago model. Klink, V. Laser capture microdissection LCM and expression analyses of Glycine max soybean syncytium containing root regions formed by the plant pathogen heterodera glycines soybean cyst nematode.
Kurata, N. An integrated biological and genome information database for rice. Libault, M. Root hair systems biology. Trends Plant Sci. Complete Transcriptome of the soybean root hair cell, a single-cell model, and its alteration in response to Bradyrhizobium japonicum Infection. The pericycle is a cylinder of parenchyma, one or at most a few cells in width, which lies in the stele immediately inside the endodermis.
The cells retain their ability to divide throughout their lives, and localized divisions in the pericycle give rise to lateral branch roots. When secondary growth occurs in roots, the vascular cambium and usually the first cork cambium originate in the pericycle.
Other cell divisions in the pericycle produce additional pericycle cells. Vascular tissues. Most dicot eudicot roots differ from eudicot stems in having a lobed column of primary xylem as their core with phloem tissue occurring as strings of cells between the lobes.
This arrangement is called a protostele. The primary xylem of monocots, on the other hand, forms a cylinder around a central mass of pith parenchyma, a siphonostele. The way in which the vascular tissues develop is useful in tracing ancestral relationships in the plant kingdom. Previous Tissues. Next Secondary Growth of Roots. Removing book from your Reading List will also remove any bookmarked pages associated with this title.
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