Analysis of gene expression and improvement by genetic engineerng for the functions of roots in higher plants

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1. Establishment of criteria for evaluating root traits and analysis of gene expression : Various kinds of root trait and embryonic development mutants of rice were obtained. A new method helpful to separating roots from soil and a new image-analyzing method useful for measuring minute roots were developed. The growth angle of the roots of juvenile wheat plants proved to be a useful criterion for evaluating root distribution. The growth direction of root proved to be determined by the interaction between geotropism and oxgen-tropism. The location of some mutant genes causing short-rootness or abnormal embryonic development was determined. The potential to regenerate roots from barley callus seemed to be controlled. The potential to regenerate roots from barley callus seemed to be controlled by some gene(s) on chromosome 2 and 3. The short-rootness of a remarkably short root mutant of rice was attributable to the decrease of the number of cells due to the decreased activity of cell peroxidase activity. 2. Nutrient uptake and metabolism : The amounts of P taken up by uppland crops proved to be related with their root masses. Root specfic activity of P uptake was apparently detarmined by soil P and specific root traits in nutrient uptake. A lot of nitrate reductase-deficient mutants indispensable for the studies on nutrient uptake and metabolism were obtained. Approximately 5x100,000 recombinant clones from spinach genomic library were screened with spinach probe. 3. Stress toierance : Deep-seeding torerance of rice varied among ecotypes. Moisture torerance of barley proved to be apparently connected with the function of roots. Cold torerance of rice proved to be evaluated approximately by the cool treatment of roots. Salt torerance of rice proved to be dur to the decrease in the uptake speed of salt transferred from roots to upper organs through intrcellular space.