The control of plant growth and development

In order for plants to grow and develop in an orderly manner there needs to be some kind of regulation of eell division, elongation and differentiation. As the plant has no nervous system, this regulation is entirely chemical in nature. The chemicals involved are ealled growth substances and there ate five main types  

Auxins - these substanees mostly eontrol cell enlargement and differentiation Most auxins are made at the apex of stems and in young leaves. 

Gibberellins - also involved in eell enlargement, but also play a key role in the breaking of dormaney in seeds and the mobilisation of seed reserves by the prodnetion of the enzyme, alpha-amylase. 

Cytokinins - assoeiated with eell division in the presence of auxins. Found in large amonnts in fruits and seeds where they are associated with embryo growth. 

Abseisie aeid - a growth inhibitor assoeiated with dormant buds and some seeds, and the closure of stomata. 

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The effects of auxin upon the growth of plants were truly remarkable. As a result of the concerted effort and interest that plant scientists devoted to this highly fashionable and exciting field of research, much of what we know of the control of plant growth and development by auxin was discovered in these highly productive years. The hormone was derived from the aromatic amino acid tryptophan and was relatively abundant in the rapidly growing meristematic parts of plants such as apical buds and root tips. Inactive bound forms existed, as in seeds, where hydroly-... 

The phenylpropanoid pathway (Fig. 3.1) is responsible for the production of many natural products that are of interest in the context of plant growth and development, human health, and ecology. For example, flavonoids are necessary for pollen viability in maize and petunia, and have been suggested to play a role in directed auxin transport. Flavonoids and sinapate esters have been found to be important UV-protectants in many species, including Arabidopsis. Furthermore, wall-bound phenolics are thought to impart control over cell wall expansion, and hydroxycinnamic acids are an important structural component of the hydrophobic barrier polymer suberin. Finally, lignin is a phenylpropanoid polymer ubiquitous in higher plants, which is necessary for mechanical support and water transport. " ... 

Auxins control many aspects of plant growth and development. Physiological processes such as cell elongation, cell division, differentiation, tropisms, rooting, fruit development and abscission are influenced by auxin [ 16,50,62]. However, the mechanism by which this hormone regulates diverse physiological processes is... 

All above-mentioned and other processes of plant growth and development take place under the control of due genes, but manifestation rate of every gene in phenotype is due to many exogenous and endogenous factors. In the process of making genetic potential of individual a features of environmental condition, the development of any feature or property... 

Earlier studies indicated that wheat cultivars responded differently to these organisms (15). If necessary, it should be possible to develop resistant varieties, especially When we know the mechanisms of plant uptake and mode of action of the toxin within the plant. One biological control may be the development of a TOX-negative inoculum for seed treatment. These bacteria may act like other rhizobacteria, which are known to increase plant growth, apparently by displacing nonbeneficial bacteria in the plant rhlzosphere (14). 

Rogers, L. A., and Campbell, M. M., 2004, The genetic control of lignin deposition during plant growth and development, New Phytol. 164 17-30. 

I believe agricultural chemistry in the next century will enter a new era in which the science of Plant Pharmacology will be developed. From knowledge of the mode of action of the plant hormones a series of compounds and combinations of these will be formulated to control and regulate plant growth and development, for human needs. 

These data show that expression of transcription factors can more efficiently modify the metabolism of plant cells by acting simultaneously and co-ordinately on different metabolic events. The manipulation of transcription factors have also shown that they are involved not just in secondary metabolism but in cell differentiation, as well as growth and development [81], and unwanted negative effects on plant growth and development may arise. This may be controllable by restricting transcription factor activity, and this could be achieved by an appropriate choice of the gene promoter which would then impede the occurrence of undesirable effects. 

Hagen, G. 1987. The control of gene expression by auxin. In, Plant Hormones and Their Role in Plant Growth and Development, ed. P. J. Davies, pp. 149-163. Boston Martinus Nijhoff. 

An attractive possibility is that stimuli which affect plant growth and development act on the systems which control endogenous amounts of lAA, and thus the stimulus is transduced into the appropriate growth or developmental response. The tropic responses and the development of secondary vascular tissue are examples of situations where careful measurement of hormone levels have shown that the levels of lAA are playing an important part in bringing about a specific response. 

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