We characterized the polyamine pathway in Petunia hybrida genotypes that were either wild type or that had been identified as having altered floral morphology. Analysis of four normal morphology lines revealed two patterns of endogenous levels of putrescine and arginine decarboxylase: two with higher levels of putrescine, two with lower levels of putrescine. Analysis of Fl and backcross progeny between high putrescine and low putrescine strains is consistent with their differences being due to a dominant allele for low putrescine content and arginine decarboxylase activity. Four Petunia mutants with floral morphology changes were also screened. One of these mutants, alf, showed high levels of putrescine and high levels of arginine decarboxylase late in development; these high levels were found whether the alfline was present in either of the two types of normal morphology genetic backgrounds that had been characterized. ment would be simply to perform crosses and test for linkage of the two traits, but the developmental anamolies were generally so severe that the flowers were completely sterile. In two cases, Mgr3 and Mgrl2 (15) we were able to obtain small numbers of Fl and backcross progeny. The phenotypes seen suggested both Mgr3 and MgrJ2 were nuclear dominant traits, and the floral phenotypes were linked to the MGBG resistant phenotypes, although the total number of progeny screened was quite small in each case.These results strongly suggested a correlation between altered polyamine synthesis and altered floral morphology, but only in the limited system ofcell culture derived tobacco plants. In order to test further the hypothesis of the involvement of polyamine biosynthesis in the differentiation of floral meristems, we undertook to characterize the polyamine content of several Petunia hybrida lines, including some with abnormal floral development.These Petunia genotypes were derived from whole plant studies as part of a search for genetic mutations in floral pigmentation and floral morphology (see Gerats et al. [8] for a brief description). These plants thus had no prior relationship with either cell culture or polyamine selections. Changes in polyamine concentration and in the activity levels of the various polyamine biosynthetic enzymes have been correlated with a wide variety of plant growth and environmental response phenomena, including cell division (9), responses to stress such as acid (21), and heavy metal (20), hormone response (3), and floral development (11,14). Polyamine-conjugates, covalently bound to phenolic acids, have also been found in high levels in plants, and may be the effectors of some of these phenomena (16).In previous reports (12, 13) we have described the isolation of tobacco cell cultures resistant to MGBG3 a potent inhibitor of SAMdc. All MGBG resistant cell lines that were successfully regenerated into whole plants revealed abnormnal differentiation of the floral meristems (14). The

Rearing techniques The experimental chamber Temperature Humidity Wave length and intensity of light Color temperatures Sampling methods and analysis of results ESULTS Moisture Responses to relative humidity gradients Responses to vapor pressure and absolute humidity gradients Effects of duration of time on survival in dry air Temperature Experiments involving slowly rising temperatures Experiments involving short-term exposures to a series of constant temperatures, at high and low humidities Experiments relating to the influence of