The growth and development of Hordeum murinum
L. seeds growing with extreme pluviometric regimes in cool greenhouse conditions were evaluated. Seven treatments according to quantity and distribution of real rainfalls of the semiarid zone of the Metropolitan Region, Chile were applied: rainy-late, normal-late, dry-early, rainy-normal, normal-early and dry-late, plus a reference without water stress, at 2/3 field capacity. The experimental design was randomized complete blocks with five replicate pots. Seeds produced in the last year were sown in pots with disinfected soil leaving the more uniform plants after emergence. Evaluations were made of phytomass production, spearing shoots of roots, the quantity of floral stems and seeds, their total weight and the proportion of seed annex structures, and the viability and germination capacity of seeds. The life cycle of dry years was shortest and with the least dry shoot matter production, the rainy-normal and normal-late years had similar dry root matter production, therefore the most important factor was rainfall distribution. All the reproductive growth values were lower than the reference. There was no seed production in both distributions of dry years and in the normal-early. There were only differences in late distributions, there were no differences among treatments in seed quality. Thus, H. murinum
uses its resources principally for seed production and late distributions determined seed production.