Cell and tissue culture studies in sorghum (Sorghum bicolor (L.) Moench);

Embryogenic callus tissue of plants were used in physiological and genetic studies. Frequencies of sorghum plantlet regeneration from embryogenic callus tissues were determined with different initiation tissues, artificial growth mediums, genotypes, and light or dark treatments. Plantlet regeneration was genotype, initiation tissue, and growth medium dependent. Genotype C401 resulted in the greatest frequency of plantlet regeneration when considering all treatments. Dorado and C401 were both regenerated at a low frequency using bisected sprout tops. All other genotypes tested only regenerated roots. Triphenyltetrazolium chloride is reduced to the red compound triphyenylformazan (formazan) by respiratory dehydrogenase enzymes and is used for testing seed viability and vigor. This reaction was tested to determine if it could be used as a rapid and reliable quantitative indicator of high respiratory activity and sorghum seedling vigor at low temperatures. Seeds from 17 sorghum genotypes were subjected to germination temperature treatments of 10, 12.5, and 15$\sp\circ$C at 2, 4, and 6 day intervals. No differences were found between time intervals. As temperature treatment increased, formazan production, shoot length, and dry shoot weight increased. There was no relationship between the production of formazan and the length or dry weight of shoots. Stability indices allowed the ranking of genotypes based on their performances over all environments. This technique was useful when trying to understand and separate genotype X environment interactions. Kaoliang genotypes known for cool tolerance were usually superior to other genotypes (tropical or temperate origin) when comparing the above traits. Proline accumulation has been related to various environmental stresses including cold tolerance. The effect of low temperature on growth and accumulation of proline in sorghum (initiated from mature embryos) and tobacco (initiated from leaf tissue) callus tissue plus sorghum seedling tissue was determined. These tissues were subjected to temperature treatments of 5, 10, 15, 20, and 25$\sp\circ$C growing on artificial medium containing 12 mM proline and no proline. Greater amounts of free proline was accumulated at 10$\sp\circ$C by sorghum callus and seedling tissues. This temperature is approximately the threshold of cold stress for sorghum tissues. Exogenous proline was absorbed by sorghum and tobacco tissues and had no influence on overall growth, and therefore, cold tolerance