Meristematic tissue

A meristem is the tissue in most plants containing undifferentiated cells (meristematic cells), found in zones of the plant where growth can take place. Meristematic cells give rise to various organs of a plant and are responsible for growth.

Differentiated plant cells generally cannot divide or produce cells of a different type. Meristematic cells are incompletely or not at all differentiated, and are capable of continued cellular division. Therefore, cell division in the meristem is required to provide new cells for expansion and differentiation of tissues and initiation of new organs, providing the basic structure of the plant body. Furthermore, the cells are small and protoplasm fills the cell completely. The vacuoles are extremely small. The cytoplasm does not contain differentiated plastids (chloroplasts or chromoplasts), although they are present in rudimentary form (proplastids). Meristematic cells are packed closely together without intercellular cavities. The cell wall is a very thin primary cell wall as well as some are thick in some plants.^{[citation needed]} Maintenance of the cells requires a balance between two antagonistic processes: organ initiation and stem cell population renewal.^{[citation needed]}

There are three types of meristematic tissues: apical (at the tips), intercalary (in the middle) and lateral (at the sides). At the meristem summit, there is a small group of slowly dividing cells, which is commonly called the central zone. Cells of this zone have a stem cell function and are essential for meristem maintenance. The proliferation and growth rates at the meristem summit usually differ considerably from those at the periphery.

Differentiated plant cells generally cannot divide or produce cells of a different type. Meristematic cells are incompletely or not at all differentiated, and are capable of continued cellular division. Therefore, cell division in the meristem is required to provide new cells for expansion and differentiation of tissues and initiation of new organs, providing the basic structure of the plant body. Furthermore, the cells are small and protoplasm fills the cell completely. The vacuoles are extremely small. The cytoplasm does not contain differentiated plastids (chloroplasts or chromoplasts), although they are present in rudimentary form (proplastids). Meristematic cells are packed closely together without intercellular cavities. The cell wall is a very thin primary cell wall as well as some are thick in some plants.^{[citation needed]} Maintenance of the cells requires a balance between two antagonistic processes: organ initiation and stem cell population renewal.^{[citation needed]}

The next step makes up the bulk of translation. It’s called elongation, and it’s the addition of amino acids by the formation of peptide bonds. Elongation is just what it sounds like: a chain of amino acids grows longer and longer as more amino acids are added on. This will eventually create the polypeptide.

Now that we’ve begun with the start codon, the mRNA shifts a little through the ribosome so that the next codon is up for grabs. Let’s say the next codon is UAU. So, now we need a tRNA that has the matching anticodon, AUA. Oh, look! Here’s a tRNA with the right anticodon, and it’s brought along a tyrosine. Tyrosine is the amino acid that is specified by the codon UAU. The tRNA attaches to the mRNA in the ribosome and lines up tyrosine right next to the waiting methionine. A peptide bond forms between the two amino acids.

Then, the first tRNA leaves everyone else behind and floats off to find more work to do. Poor methionine! Now it’s just drifting around like a lonely kite in the wind! That tRNA left methionine hanging by only one anchor: its peptide bond with tyrosine. The tyrosine is still attached to its own tRNA, which, in turn, is clinging to the mRNA inside the ribosome. Already we can see the beginnings of a polypeptide elongating outward.

The ultimate success of micropropagation on commercial scale depends on the ability to transfer plants out of culture on a large-scale, at low cost and with high survival rates. Tissue culture conditions that promote rapid growth and multiplication of shoots often result in the formation of structurally and physiologically abnormal plants. The tissue culture plants are often characterised by abnormal leaf morphology and anat0my’ poor photosynthetic efficiency, malfunctioning of  tomata and a marked decrease in epicuticular waxes. Qualitatively also, the waxes present on the surface of the leaves of ill vivo and ill vitro raised plants may vary. The heterotrophic mode of nutrition and poor mechanism to control water loss render micropropagated plants.

vulnerable to the transplantation shocks. Although considerable efforts have been directed to optimise the conditions for the ill vitro stages of micropropagation, scant attention has been paid to understand the process of acclimatisation of micropropagated plants to the soil environment.

Successful transplantation of plants to the field requires a sound knowledge of silvicultural practices generally employed in the nursery for the propagation of plants. Sometimes, there is a tendency to use small vials for initial stages of transplantation; this causes root curling. Such plants, if transplanted, may survive but often show drastic reduction in growth at later stages. Further, it should be realised that plant propagation via tissue culture differs from the onventional methods of propagation in several key aspects. Unlike nursery seedlings or cuttings, the tissue culture plants are raised under perfectly controlled conditions. Since, under ill vitro conditions, plantlets are grown under very high humidity and on a sucrose rich medium, they require gradual
acclimatisation to the field conditions. The transfer of individual plantlets to potting mix and their acclimatisation under specified conditions of humidity, temperature and light requires special facilities and is, therefore, very expensive.