NotesL14-16 - BioSci 1C - Winter quarter, 2008 Outline of...

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BioSci 1C - Winter quarter, 2008 Outline of lectures 14-16 Development is a general term describing what organisms do to complete their life cycles and reproduce. Developmental events may be part of the genetic program of a plant which directs the plant (or individual plant structures) to change at various points along the progression through the life cycle. This aspect of development involves the orderly turning on of some genes, the turning off of other genes, and more subtle aspects of regulation of genes. This part of development generally proceeds over a relatively broad time frame and generally involves plants or plant parts taking on new forms ( morphogenesis ) and the conversion of unspecialized cells into cells with specialized forms and functions ( differentiation ). You have seen examples of this sort of development in the lab and heard about it in lectures. Unspecialized cells in the protoderm carry out a series of cell divisions in different directions to establish the guard cell complex of the stomata. Cells of the procambium elongate, develop secondary cell walls in different patterns and degrees of completion, and then die to form water-conducting xylem elements. The cell wall in localized areas of root epidermal cells grows out to form root hairs. Exactly how the genetically identical cells of a plant are guided along specific developmental pathways at specific times and locations in the plant's life is not well understood. It is clear, however, that an important aspect of the control of differentiation is the correct turning on or off of genes and, therefore, the presence or absence of proteins that the genes encode. In many cases, the coordination of these internally determined (i.e., genetically programmed) developmental processes is coordinated by cell or tissue production of and subsequent response to internal chemical signals that are often called plant hormones (see below). 1. The term development can also be applied to those generally unscheduled changes plants undergo in order to make an effective response to the living and non-living elements of their environments. This part of plant development may not involve permanent changes in plant form or specialized cell functions. The changes may involve changes in the enzymes in a cell; changes that make it possible for the cell to do different metabolic things (i.e,, enzyme-catalyzed reactions) from those it has been doing. In order to respond to its environment a plant must be able to "sense" its environment. Plants have an assortment of senses, although they do not work like ours do. We have senses of hearing, sight, smell, taste and touch. Plants don't have these senses, but they can respond to most of the kinds of stimuli that we respond to. Plants do not see, but they respond to a greater range of the wavelengths in the electromagnetic spectrum than we do. Plants do not smell or taste, but these senses of ours are responding to various
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This note was uploaded on 09/10/2008 for the course BIS 1c taught by Professor Maloof during the Winter '07 term at UC Davis.

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NotesL14-16 - BioSci 1C - Winter quarter, 2008 Outline of...

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