Stamen System

The Androecium or Stamen System.—The andracium is the single or double whorl of male organs situated within or above the corolla. It is composed of stamens or microsporophylls. 

UNDERBRINK, A. G., SCHAIRER, L. A. and SPARROW, A. H. Tradescantia Stamen Hairs A Radiobiological Test System Applicable to Chemical Mutagenesis , ibid., Vol. 3, p. 171. 

Five plant systems or types of study have been selected for coverage in this report plant cytogenetic analysis, chlorophyll mutations, the Tradescantia stamen hair test, the maize waxy locus system, and plant metabolic activation systems. Descriptions of other plant systems may be found in the proceedings of workshops on the use of higher plants as monitors for environmental mutagens94 and on the use of pollen systems to detect biologic activity of environmental pollutants.71... 

Burton, and F.J. de Serres. Exploratory monitoring of air pollutants for mutagenicity activity with the Tradescantia stamen hair system. Environ. Health Perspect. 27 51-60, 1978. 

Underbrink, A.G., L.A. Schairer, and A.H. Sparrow. Tradescantia stamen hairs A radiobiological test system applicable to chemical mutagenesis, pp. 171-207. In A. Hollaender, Ed. Chemical Mutagens ... 

A few examples include the mouse specific-locus test for germ-cell mutagenesis (Russell 1994 Russell 1989), tests for forward and reverse mutations in the ad-3 region of Neurospora crassa (de Serres and Kolmark 1958), the Tradescantia stamen-hair system (Underbrink et al. 1973), and the rlllocus test for bacteriophage T4 (Drake 1963). Many others could be noted. 

The need for a system with useful principles of classification has long existed, and the progress of research has changed the character of these systems. Thus, the system, introduced by Linne (Linnaeus), was a purely artificial system for phanerogams, built on the structure of the flower and the number and arrangements of stamens and pistils. 

The techniques for using the stamen-hair system have been developed over the past several years specifically for radiobiological studies. However, preliminary experiments indicate that these techniques are applicable to chemical mutagen studies in either a gaseous or liquid state. Several years ago. Smith and Lotfy ) showed that certain gaseous chemicals, specifically ethylene oxide, ketene, and methyl chloride, produced chromosome aberrations in pollen tubes of Tradescantia paludosa cultured to metaphase. More recent experiments have also employed microspores. 

Only preliminary experiments have been undertaken to date, to evaluate the potential usefulness of the stamen-hair system for chemical-mutagen studies, but development of the system was continued to further improve its radiobiological usefulness. The established techniques used in physical mutagen testing will be described here. 

Although many tissues or organs of this plant may be used efficiently in various experimental procedures (Table 1), this chapter will be concerned primarily with a detailed description of the procedures currently being used in handling the Tradescantia clone 02 stamen-hair system. Certain other Tradescantia clones, heterozygous for flower color, may be handled in the same way. >26,29,31)... 

Techniques for the successful and efficient radiobiological use of the stamen-hair system have been evolved during the last decade, but its... 

During the course of an experiment, an adequate number of control stamen hairs must also be scored, preferably a number nearly equal to the number scored for the lowest exposure used. Seven separate experiments were necessary to construct the X-ray and neutron dose-response curves down to values less than 1 rad. Separate controls were scored for each experiment, and the results are shown in Table 2. For each of these experiments, the frequency of spontaneous pink mutant events per stamen hair (total mutant events/total hairs taken through a 5-day scoring period), standard errors, total numbers of stamen hairs, and the total number of mutant events are listed. These control values are for the most part very low, which illustrates the relatively high stability of the system. 

III. CHARACTEMSTIC DATA OBTAINED FROM THE STAMEN-HAIR SYSTEM... 

Thus, handled properly, the stamen hair system of Tradescantia clone 02 can provide some unique mutagen information. Besides the resemblance of the growing stamen hair to a small cell culture colony, it has further advantages in that visible aberrant or mutant cell types are produced and cell lineage is clearly defined. In addition, the system is easily handled so that statistically adequate populations are usually readily obtained. Its advantage over a bacterial system is that it has eukaryotic chromosomes and is very sensitive to physical and chemical mutagens. 

Detailed procedures for the proper and efficient handling of the Tradescantia clone 02 stamen-hair system are given. The techniques de-... 

Specific areas discussed include advantages and uses of the stamen-hair system, review of floral and stamen-hair morphology, cultivation of stock plants, screening of untreated plants for abnormally high aberration rates, preparation and handling of cuttings for experimental use, and consideration of flower production and of statistically acceptable numbers of cuttings and stamens rec[uired for a typical experiment. 

Although there are many advantages offered by the stamen-hair system, it is of particular interest because it has a eukaryotic nucleus, is heterozygous for blue-pink flower color genes, and may be employed in numbers sufficient to detect very low levels of radiation (and presumably of chemical mutagens) that might not be practical with many other types of organisms. Consideration of numbers of stamen hairs scored in several previous radiation experiments at several dose levels and the standard deviations obtained made it possible to calculate numbers of stamen hairs theoretically needed to come within desired limits of error down to very low doses. 

Descriptions of the types and combinations of visible somatic mutations or aberrations found in stamen hairs and details of the computer-oriented scoring techniques are given. Several types of data characteristically obtained from the stamen-hair system are discussed. These include cell mutation frequencies and their dose-response curves, relative biological effectiveness, cell survival curves, mutation rates, and relationships of specific aberrant cell types to each other, to the cell number in the hair, and to their positions within the hair. 

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