![]() ![]() The subsequent accumulation of cell division and enlargement in this bundle of tissue gives rise to a new structure known as the root primordium. This pattern of growth gives rise to a bundle of tissue. Localized cell divisions in the Pericycle give rise to the lateral root primordia. Before the emergence of lateral roots in the morphogenetic process, a new lateral root primordium which consists of primordial cells is formed. They provide physical support and uptake water and nutrients for growth. Lateral roots are one of the most important tissues in a plant's anatomical structure. Auxins have a large impact on plant primordium development because of their effect on gene regulation. Higher concentrations allow them to bind to cells and results in downstream effects that lead to primordial growth. Auxin concentration gradients are necessary to initiate and continue primordial growth. This has led researchers to believe that auxin accumulation as well as decreases in auxin levels might control different phases of primordium development. It affects transcription factors that control the upregulation or downregulation of auxin genes that relate to growth. It is believed to control these processes by binding to a specific receptor on plant cells and influences gene expression. There is a lot of current research being conducted to explain the role that it assists in the process of plant primordium. ![]() ![]() Auxin concentrations affect mitosis, cell expansion, as well as cell differentiation. Auxin's Role in Primordial Development Īuxin is a group of plant hormones, or phytohormones, that plays a key role in almost all areas of the growth and development of plants. At least in wheat plants, leaf primordium initiation rates increase with increasing ambient temperature, and the leaf number of some varieties decrease with increasing daylength. Primordia are initiated by local cell division and enlargement on the shoot apical meristem. The process of lateral root primordium initiation has been studied in Arabidopsis thaliana, though the process in other angiosperms is still under analysis. Though primordia are typically only found in new flower and leaf growth, root primordia in plants can also be found, but are typically referred to as lateral root primordium or adventitious roots. In pines, the leaf primordia develop into buds, which eventually elongate into shoots, then stems, then branches. Primordia initiation is the precursor for the start of a primordium, and typically confers new growth (either flowers or leaves) in plants once fully mature. This bulging is caused by slower and less anisotropic, or directionally dependent, growth. Flower primordia start off as a crease or indentation and later form into a bulge. Flower primordia are the little buds we see at the end of stems, from which flowers will develop. These new leaves form near the top of the shoot and resemble knobby outgrowths or inverted cones. Leaf primordia are groups of cells that will form into new leaves. There is still much to understand about the genes involved in primordium development. The plant hormone auxin has also been implicated in this process, with the new primordium being initiated at the placenta, where the auxin concentration is highest. Genes including STM (shoot meristemless) and CUC (cup-shaped cotyledon) are involved in defining the borders of the newly formed primordium. The process of primordium development is intricately regulated by a set of genes that affect the positioning, growth and differentiation of the primordium. Primordium development in plants is critical to the proper positioning and development of plant organs and cells. Plants produce both leaf and flower primordia cells at the shoot apical meristem (SAM). ![]()
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