Natural selection is acting to promote various but some typical types of developmental processes. These two processes are responsible for the change in the shape and size of a plant and its various organs. These two processes share no casual relationship. Growth of plant cells depend mainly on water consumption although they consume many other compounds also the cell division of plant cells consist of the duplication of nucleus and the building of cell wall to separate the two new nuclei.
The parent cell gives rise to complete two daughter cells. A plant shoot is approximately a cylinder so it is convenient to use a cylindrical coordinate system to indicate position on a shoot. Cell division is classified into three types according to the orientation of the new cell wall with respect to the three mutually orthogonal directions of the cylindrical coordinate system. In transverse cell division, the new cell wall is roughly orthogonal to the axis of the shoot, in periclinal cell division the new cell wall is parallel to the surface of the plant and in anticlinal cell division the new wall is contained in a plane passing through the axis of the shoot.
The embryonic development results in seed or spore. After dormancy period is over seed begins to absorb water and cells undergo expansion, this results in the bursting of new plant, this is known as germination. After germination, if all goes well, the seedling has a root growing down into the ground and a shoot growing up from the ground.
The line formed by the root and shoot form the main axis of the plant. In meristematic development, some species of plants have meristems that are present before germination while in other species the meristems form after germination.
In the plant, there may be present a clear boundary between embryonic and meristematic development. The entire plant organ develops from the primodium. The type of cells that develop is not completely determined until after the formation of the primordium.
A variety of factors decide which type of plant organ develops. Development of seedling Plant embryogenesis is followed by germination. Germination marks a switch from an anabolic phase of nutrient accumulation to a catabolic phase of nutrient consumption and growth. There are two stages separated by period of quiescence, where embryo become desiccated and is stored in seed. Light: It enables seedling to extend through soil in dark and then switch to vegetative growth once it has emerged at surface.
It is controlled by abscisic acid and gibberlic acid. Abscisic acid inhibits growth and gibberellic acid promotes growth. There are number of genes which affect transition when mutated but are not involved in hormone synthesis. Instead these genes encode regulatory proteins that control downstream embryo specific and seedling specific gene expression.
Elsevier, London, pp 85— Google Scholar. Endress PK Diversity and evolutionary biology of tropical flowers. Endress PK Symmetry in flowers: diversity and evolution. Fukushima K, Hasebe M Adaxial-abaxial polarity: the developmental basis of leaf shape diversity. Taxon — CrossRef Google Scholar. Sassi M, Traas J When biochemistry meets mechanics: a systems view of growth control in plants. Yamaguchi T, Nukazuka A, Tsukaya H Leaf adaxial-abaxial polarity specification and lamina outgrowth: evolution and development.
Citerne 1 1. Personalised recommendations. Cite entry How to cite? All data are the mean values for each plant considered. Experiments were repeated twice, and similar values were obtained in each experiment. Primers used for plasmid construction are listed in supplementary material Table S1. The transformation of Arabidopsis plants was performed via floral dipping using Agrobacterium tumefaciens strain C58MP90 Clough and Bent, GUS staining, fixation, and whole-mount clearing preparation of roots were performed essentially as described previously Malamy and Benfey, , and samples were observed with a Leica DM microscope equipped with Nomarski optics Leica Microsystems, Wetzlar, Germany.
Images were taken every 5 minutes and processed with ImageJ software. S1 Okushima et al. LR formation in the lbd arf and lbd arf double mutants, however, was strongly reduced, suggesting that the potential to form LRs retained in the arf and arf single mutant is partially dependent on LBD16 supplementary material Fig. Then, their two nuclei migrate towards the common cell wall, establishing cell polarity.
After that, both LR founder cells divide asymmetrically, thereby producing two small daughter cells and two larger flanking cells. In this assay, root gravitropic bending induces auxin accumulation at the outer side of the curvature, which could in turn induce LR formation at the bending point Laskowski et al. After about 11 hour, two nuclei of the pair of XPP cells migrated towards the common cell walls, followed by the first anticlinal ACDs Fig.
As shown in Fig. Both reporter genes are co-expressed during early stages of LR initiation. The yellow arrowheads indicate the initial position of the nucleus and the orange arrowheads show the position of the nucleus after migration. The yellow arrowheads indicate the initial position of the nucleus and the aqua arrowheads show the divided nucleus. In A and B, the time hour:minute after the gravistimulation is indicated in each panel.
The pictures shown in the three panels were taken using the same camera settings. The arf arf was used as arf7 arf19 in this experiment. The arrowheads indicate emerged LRs. The error bars indicate s. The arrowheads indicate cell wall. The lbd and the lbd single mutations slightly reduced the number of LRs without affecting the primary root growth, whereas the lbd single mutation had no inhibitory effect on LR formation Fig.
S3 Okushima et al. The lbd lbd double mutant had decreased LR density as previously reported supplementary material Fig. S3 Lee et al. We found that the lbd lbd lbd triple mutant showed more reduction of LR number Fig. We also found that, although the LR initiation density number of non-emerged LR primordia and emerged LRs per primary root in lbd lbd lbd was lower than that of wild type, the non-emerged LR primordium density number of non-emerged LR primordia per primary root of lbd lbd lbd was higher than that of wild type supplementary material Fig.
In addition, we found that the lbd lbd lbd mutant had more pre-LR initiation sites with DRGUS activity than wild-type Col, but the lbd lbd lbd mutations did not affect the density of pre- and post-initiation sites with DRGUS activity supplementary material Fig.
S4C , suggesting that the lbd lbd lbd mutations decrease LR initiation events without affecting the specification of LR founder cells.
However, LR primordia at Stage I after ACDs were observed in the lbd lbd lbd mutant, suggesting that the asymmetry of the LR founder cells was established in the lbd lbd lbd mutant supplementary material Fig.
SRDX is an artificial repression domain for the construction of chimeric repressors of transcriptional factors, which is originally identified from EAR-motif repression domain Hiratsu et al.
SRDX-fused transcriptional activator dominantly represses the transcription of its target genes, even in the presence of endogenous and functionally redundant transcription activators Hiratsu et al.
CycB1;1-GUS expression in root tip and mature root region is shown. These phenotypic differences might be due to the differences in their promoter activity, protein stability or effect of transcriptional repression among these LBDs-SRDX proteins. In wild type, the nuclei of two adjacent XPP cells migrate to the common cell walls to establish the asymmetry of these cells before the first ACD for LR initiation.
However, these symmetrically divided XPP cells in LBDSRDX plants did not show additional divisions until 32 hours after gravistimulation, at which time a few rounds of divisions were usually observed in the wild-type plants. B Root elongation of seedlings on NAA-free, 0. The data are represented as growth of primary root relative to growth on NAA-free medium. The error bars represent s. The arrowheads indicate cell wall positions. In multicellular organisms, cell differentiation mediated by ACD is important for the development of new organs.
In flowering plants, LRs are formed from the apparently differentiated pericycle cells adjacent to the XPP, which divide asymmetrically to produce central small and flanking large cells with different fates De Smet et al.
However, it remains unknown how auxins regulate this initial step of LR initiation. It is known that the slr-1 mutant has higher auxin content in the root, which seems to be due to disturbed auxin homeostasis Vanneste et al.
The arrowheads indicate the cell wall. SRDX technology has been utilized in several studies of transcriptional factors to overcome functional redundancy Hiratsu et al. Although expression of SRDX-fused transcriptional activators might have unexpected effects, including competing with unrelated proteins for DNA binding or might form aberrant transcriptional complexes, the various transgenic plants expressing SRDX-fused transcriptional activators exhibit a phenotype similar to the loss-of function mutants Hiratsu et al.
S6 Brady et al. Recently, Berckmans et al. Berckmans et al. In the LBDSRDX plants, it was not confirmed whether the new initiation events occurred between existing LR founder cells or whether the number of primed cells were increased in the basal meristem.
Unfortunately, we could not detect the increased auxin response maximum in the lbd16 lbd18 lbd33 triple mutant in which both LR initiation and LR primordium development and emergence were inhibited supplementary material Fig.
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