Types of Plant Tissue Culture

Although plant tissue culture should refer only to those of unorganized aggregates of cells, it is commonly used as a collective term to describe all types of in vitro plant cultures (George and Sherrington, 1984). 

Unorganized growth occurs frequently when pieces of whole plants are cultured in vitro. The tissue lacks any recognizable structure of the original intact plant. 

Food Products Color Flavors anthocyanms, betacyanins, saffron apricot, banana, apple, cherry, grape, peach, pineapple, rasberry, strawberry, asparagus, capsicum, celery, tomato, vanilla, cocoa 

Pharma- ceuticals Alkaloids ajmalacine, atropine, berberine, camptothecin, ceuticals codeine, hyoscyamine, quinine, morphine, scopolamine, serpentine, vinblastine, vincristine 

Agricultural Chemicals pyrethrins, rotenone, azadirachtin. neriifolin, salannin, alleopathic chemicals 

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Most research into in vitro foreign protein production has been undertaken using cell suspensions. However, other forms of plant tissue culture such as hairy roots and shooty teratomas have also been tested in a number of studies (Table 2.1). The characteristics of different types of plant tissue culture and their utility for large-scale foreign protein production are outlined in the following sections. 

A number of different types of plant tissue cultures (e.g. suspension cultures, differentiated cultures, immobilized cultures, and transformed cultures) have been studied for the production of flavouring substances [14-19]. As de novo biosynthesis has been found unsuccessful in most cases (exceptions are shown in Tab. 3.5.), biotransformation of added precursors has been studied extensively. Fig. 3.4 shows some examples of biotransformation of terpenes by suspension cultures. Tab. 3.6 lists some biotransformations by suspension or immobilized cultures. 

The induction of PAL activity at the onset of vascular differentiation can be shown by the use of plant tissue cultures (37-39). Xylem cells with secondary and lignified walls are differentiated over a time course of 3-14 days by the application of the plant growth factors naphthylene acetic acid (NAA) and kinetin in the ratio 5 1 (1.0 mg/liter NAA, 0.2 mg/liter kinetin) to tissue cultures of bean cells (Phaseolus vulgaris) (37,40). The time for differentiation varies with the type of culture, solid or suspension, and with the frequency and duration of subculture, but for any one culture it is relatively constant (37,41,42). At the time of differentiation when the xylem vessels form, the activity of PAL rises to a maximum. The rising phase of the enzyme activity was inhibited by actinomycin D and by D-2,4-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide (MDMP) applied under carefully controlled conditions (42). This indicated that both transcription and translation were necessary for the response to the hormones. Experiments using an antibody for PAL and a cDNA probe for the PAL-mRNA have also shown that there is an increase in the amount of transcript for PAL during the formation of lignin when Zinnia mesophyll cells are induced to form xylem elements in culture (Lin and Northcote, unpublished work). 

Herbicide-resistant plant varieties have proven to be valuable experimental tools In determining the molecular mode of action of herbicides (2,8). In addition, such varieties are likely to be an Important source of selectable markers for use In plant molecular genetics and In the engineering of resistant crop species ( ) The earliest herbicide-resistant blotypes described arose spontaneously from weed populations which had been repeatedly exposed to a herbicide (10,11). More recently, mutagenesis and selection on defined media have been used to Isolate herbicide-resistant or herbicide-tolerant mutants of higher plants from populations of cells In tissue culture (4,5.7,12). While the use of plant tissue culture has proven useful for Isolation of some types of mutants, the... 

Because of cell speciaHzation, some produces are produced in cultures of those cellular types. Three main classifications of the types of plant cell and tissue cultures are ... 

A vector that facilitates high-level protein expression in plant tissue culture, particularly a transient expression system that could be applied to existing wild-type cultures, would be advantageous for in vitro foreign protein production. However, such a system has not yet been developed. The success of this approach depends in part on whether appropriate levels of viral infection, replication and transmission can be established within tissue culture systems. 

The primary focus of isotopic studies on human bone has revolved around the distinction between consumption of C3 plant material and plant material Some years ago, it was discovered that the C3 (or Calvin) and the (or Hatch-Slack) photosynthetic pathways generated plant tissue with quite different abundances, an approximately 15 parts per thousand (0/00) difference in the isotopic ratio ( ) This isotopic difference between two types of plants is the main basis for most studies of human diets that have used stable isotopes of carbon as an analytical tool Most plants in temperate areas are of the C3 type, but corn (maize) is a plant and is of special interest to archaeologists because of the apparent dependence of many cultures on maize agriculture ... 

There has been considerable speculation regarding connection between "Kranz" anatomy and the physiology of C type carbon assimila-tion(l),Plant tissue culture offers an opportunity to study the mechanism of photosynthesis at cellular level. Development of photosynthetic apparatus has been studied in several dicot callus cultures(2). However it has been relatively difficult to induce greening in callus cultures derived from monocot C. plants (3). The present investigations were undertaken with an object to study the chloroplast development in the callus cultures, derived from a monocot C. plant maize, in relation to "Kranz" anatomy and chloroplast dimorphism. 

In vitro development of cells and tissues depends on different factors such as genotype, type of plant, age and developmental stage of an explant, physiological state of an explant-donor plant, and the external environment which includes composition of media and physical culture conditions (light, temperature) (Gaj, 2004). 

Notably, many types of naphthoquinones and anthraquinones are synthesized and accumulated in plant tissue cultures. This fortuitous situation has facilitated much recent work on the biosynthesis of naphthoquinones and anthraquinones (Ellis, 1988 Leistner, 1981, 1986 Simpson, 1986). Plant tissue cultures often do not accumulate other types of secondary metabolites. Although naphthoquinones and... 

Plant cell and tissue cultures are excellent systems for the production of secondary metabolites. O Dowd and colleagues examined the influence of different types of plant growth regulators on alkaloid content of callus derived from different species... 

Success in structural studies of cell walls depends largely on the purity and homogeneity of the cell wall preparations examined. Some studies have been made of primary cell walls extracted from whole plant tissues. Since all tissues of intact plants contain a variety of cell types, the walls prepared from these tissues are not homogeneous. The desire for homogeneous wall preparations has been satisfied by use of suspension-cultured cells. Suspension-cultures, of at least some types of plant cells, can be maintained in a totally undifferentiated state. These types of suspension cultures provide a source of homogeneous primary cell walls. 

The studies of Criddle et al. [17] on carrot and tomato cell cultures outlined basic procedures for isothermal heat rate measurements of plant tissues. Samples are placed in an ampule, sealed to prevent any water vapor loss, placed in the calorimeter at the desired temperature and the heat rates recorded directly. Figure la shows the type of thermogram obtained. There is an initial rapid change in recorded heat rate while sample and ampules are thermally equilibrated. Following equilibration, (about 45 min in this example) the amplitude of the thermal signal is corrected for baseline values obtained with empty ampules to yield the sample metabolic heat rate. Temperature may then be adjusted to new values to establish temperature coefficients of heat rate or the ampules may be opened and the sample environment modified before the ampule is resealed and re-equilibrated for evaluation of effects of the modification on plant activities. Because plants are ectotherms that live in a variable temperature environment, temperature dependence studies using sequential i.sothermal mea.surements are essential for characterization of plant physiological properties. 

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