Mutational Mosaic Coat Patterns of the Guinea Pig.
TABLE OF CONTENTS PAGE INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 The Color Factors of Guinea Pigs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 A Somatic and Germinal Mosaic (Ccd+Cdcd). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Two Intense-dilute Mosaics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 An Agouti-black Mosaic ( A A +aa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 Two Intense-dilute Mosaics ( F f + j ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 An Intense Brown-pale Brown Mosaic (Pp+pp). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 DISCUSSIOV.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 LITERATURE CITED.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
The Occurrence of Three Recognized Color Mutations in Mice
To sum up the facts above recorded it may be stated that: 1. A previously recorded mutation of the gray-bellied agouti pattern, known as white-bellied agouti, has arisen in two experiments on color inheritance in mice. 2. In experiment A it has arisen independently three times in a hybrid race of mice. 3. In this experiment there has been no selection in the direction of the mutation. 4. In experiment B it has arisen once in an inbred race in which selection was being carried on. 5. In this race the mutation represents a variation in exactly the opposite direction from that in which the selection was being made. 6. A recessive pink-eyed mutation has occurred in a closely inbred dilute brown race. A similar mutation has appeared in a hybrid race into which one animal from the dilute brown race probably introduced the mutation. 7. A mutation involving loss or suppression of the black producing factor has arisen in a stock of inbred wild mice. This has caused the appearance of brown agouti young. 8. The wild race in which this occurred is related to the hybrid race (see conclusion 2) in which the white-bellied agouti mutation appeared three times. The suggestion is offered that a tendency to germinal instability may have been transmitted by male 131 a common ancestor of both races.
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.