Measuring genome size of desert plants using dry seeds

Use of seeds instead of leaves for the flow cytometric measurement of DNA content is of particular interest to botanists and plant ecologists, since it allows estimation of genome sizes for species having reduced leaves or that accumulate staining inhibitors within leaves, and also for species growing in regions where cytometers are not readily available. The seeds of 24 desert species, including wildflowers, cacti, shrubs, and trees were analyzed by flow cytometry. Nuclei were used from either total seeds or seed tissues, following dissection to determine the seed parts that were most suitable for genome size measurement. In addition, the mass of 100 seeds was established. The seeds of 14 species contained only cells occupying a mitotic cell cycle. For 10 other species, endoreplicated nuclei (up to 32C) were detected. Using entire seeds or their parts, it was possible to estimate genome sizes for all of the species, which ranged from 0.79 pg per 2C in Parkinsonia aculeata L. to 26.96 pg per 2C in Agave parryi Engelm., thus this kind of plant material can be used for the cytometric measuring of nuclear DNA content. However, a detailed understanding of seed biology is needed to interpret the results correctly. The relationships among genome size, seed mass, and desert growing conditions are also discussed.