INVESTIGATION OF POSSIBLE CYTOLOGICAL EFFECTS ON SHRUBS FROM CHRONIC LOW-LEVEL RADIATION AT NTS (PROGRESS REPORT) W. A. Rhoads and Diane M. Varney EG&G, Santa Barbara Operations ABSTRACT Evidence of radiation damage to vegetation at NTS has been found only at the morphological or phenological levels and in the vicinity of nuclear cratering experiments, or in fallout patterns of accidental ventings of radioactive debris. Some effects have been noted in controlled experiments around large gamma radiation sources, also. Possible effects at the cytological level at lower radiation doses are also of interest. Because there have been annual species which have been irradiated in all stages of their life cycles for a number of generations, these species are of special interest; however, unfavorable precipitation did not produce sufficient annuals in either 1974 or 1975 for examination. Shrub species are also of interest, and one shrub, Artemisia spinescens, was found to have cells at the proper stage for examination (chromosomes number after meiosis equal nine). At Site D, Area 11, irradiated since 1954-1955 to estimated doses of 35 to 140 R, 5 percent of the cells producing pollen were aberrant compared with 1.7 percent of the cells from plants outside the irradiated area. Because of the small numbers of cells examined, these numbers were not, however, considered adequate to provide more than an indication that there were more aberrants in the irradiated areas than in the nonirradiated. INTRODUCTION The search for radiation effects within areas contaminated with radioactive materials at the Nevada Test Site (NTS) has been carried out in the field almost from the start of testing of nuclear devices there. To date, evidence of radiation damage to vegetation in Nevada has been found only at the morphological or phenological level, and these radiation effects have all been in the vicinities of nuclear cratering experiments, or in the fallout patterns of accidental ventings of radioactive debris. Some vegetation effects have also been noted adjacent to large gamma radiation sources set up in controlled experiments around the test site (Kaaz et al., 1971; Rhoads et al., 1969). 111