Observation of High-frequency Occurrence of Chimeral Adventitious Shoots in Tissue Culture from the Chimeral Tissues of Pelargonium zonale

In Pelargonium, the plastid mutation in three independent cell layers L1, L2, and L3, can produce plastid chimeras with visible shoot colour difference such as GWG (green-white-green) and GGW (green-green-white). Chimera can be used to trace the relationship between the cell layers of different genotypes during shoot development and the effect of the mutated genes on shoot development. In this study, we have obtained different adventitious shoots with GGG, GWG, GGW, and WWW combinations of cell layers through tissue culture of petioles and internodes from GGW and GWG chimeras of Pelargonium zonale `Mrs Pollock'. Much higher percentage (14.9%) of chimeral adventitious shoots was obtained from GGW tissues than from GWG tissues (4.2%). Of the 10.8% chimeral adventitious shoots regenerated in this experiment, 8.6% are different from the original type of explants. This result indicated that cells at least in both L2 and L3 of the explants were involved in the regeneration of the adventitious shoots. The number of shoot types regenerated is likely dependent on the number and the type of cells that were in direct contact with the culture medium. It is suggested that the mixed cells can be used to produce the chimera by tissue culture. Three possible ways to form the chimeras in vitro culture were discussed. Chemical names used: TDZ =1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea (Thidiazuron); IAA = Indole-3-acetic acid; PVP = polyvinylpyrrolidone.

Untersuchungen über die photooxydative Farbstoffzerstörung und Stoffwechselhemmung bei Chlorellamutanten und panaschierten Oenotheren

1. The influence of light on respiration, glucose uptake and pigment content was studied in the α- and β-carotin lacking Chlorella mutant 9 a isolated by Claes. The assimilation of glucose is inhibited even by very small amounts of blue light, while the consumption of O2 and the pigment content remain unchanged. The pigments are destroyed only at higher intensities of light; along with it goes an increased consumption of O.,. Red light is much less effective than blue light. Normal photosynthesis could not be observed either by the manometric method or by using 14CO2.2. Under anaerobic conditions there is no destruction of pigments even at high intensities of light. The inhibition of oxidative assimilation, however, is only partly prevented, as shown by experiments on the assimilation of glucose in the dark after illumination under anaerobic conditions.3. Also in variegated Oenothera strains, no matter whether they are the result of plastid mutation 1 or of hybridisation. the bleaching can be prevented by the withdrawal of O2.4. The results correspond to the findings of Griffith and coworkers with blue green mutants of purple bacteria. The fact that in variegated Oenotheras carotin is present speaks against the assumption of these authors that photosensitiveness generally is caused by the deficiency of carotins. The stronger action of blue light indicates that also the carotins may have a photodynamic effect.

MATERNAL INHERITANCE OF LEAF VARIEGATION IN HEXAPLOID WHEAT

A P32-treated vulgare wheat plant produced an offspring having yellow-green stripes on the leaves. The variegated leaf character is maternally inherited. Progenies of individual variegated selfed plants differ widely in the proportions of green: variegated individuals. Green sibs of variegated plants breed true. In crosses between variegated awn-tipped and green bearded plants, the awn character segregated in a simple Mendelian fashion while the variegation appeared only in individuals whose maternal parent was variegated. Plastid mutation independent of chromosomal genes is presumed to have occurred in the P32-treated parent of the original variegated plant. On the plastid-mutation hypothesis, variegated plants have two kinds of plastids, normal and mutant, and either or both kinds may be represented in the eggs produced. When both kinds of plastids are present, segregation during embryo development may result in the variegated effect seen in the older plants.

AN IRREVERSIBLE GENE-INDUCED PLASTID MUTATION

When plants of a variegated barley are self-pollinated, they produce few variegated and many albino offspring. In different years the proportion of albino plants has ranged from 80.2 to 93.1% of the total population. Seed from heads having much green tissue gave rise to a much larger proportion of variegated plants than did seed from heads with more white tissue. Maternal inheritance of plastids is probably the cause of this difference. In crosses F1 plants are green, variegated, or albino if the ♂ parent is variegated, but if the ♂ parent is green all the progeny are green. The albino plastids thus apparently do not mutate back to normal in the presence of the normal gene. In some F2 populations deviation from a ratio of 3 green: 1 others is insignificant, in other populations significant deviations, attributed to irregularities of plastid mutation and segregation, occur. F3 results support the hypothesis that a single pair of genes affecting plastids is segregating in hybrids. The normal (green) gene is dominant if "green" proplastids are present in the egg but not dominant if the proplastids are all "white". From cytological observations on sperms and eggs as well as from the genetic results, it is considered likely that direct plastid transmission to zygotes is exclusively from the female parent.

GENETICAL STUDIES ON MUTANTS IN THE PROGENY OF HEAT-TREATED BARLEY

Heat treatments were applied to barley seeds and 10 different mutant characters were observed in the progeny, viz.; xantha1 and 2, dwarf1,2,3 and 4, virescent1 and 2, chlorina and albino. Typical Mendelian ratios were not obtained in the first segregating generation owing to the small size of the sector affected in the generation of treatment. In the second and third segregating generations, good fits were obtained in all cases to either monohybrid or dihybrid ratios. Both 3:1 and 15:1 ratios were observed in lines segregating for xantha1 and albino characters. The postulation of the duplicate factor hypothesis was necessary to explain this situation. Chlorina and dwarf mutants segregated in all the cases investigated as simple Mendelian recessives. One virescent strain was believed to have arisen through plastid mutation and was maternally inherited.The heat treatment significantly increased the natural mutation rate for the xantha characters but apparently had no effect on the albino mutation rate. Dwarf, virescent and chlorina mutants were observed in the segregating generation after heat treatment, but were not detected in untreated populations.