An Anatomical Comparison of the Roots, Stems and Leaves of Big Bluestem (Andropogon Gerardi), Side-Oat Grama (Bouteloua Curtipendula) and Blue Grama (Bouteloua Gracilis) at a Three-Week Stage of Development

Big bluestem (Andropogon gerardi), side-oats grama (Bouteloua curtipendula) and blue grama (Bouteloua gracilis) represent a tall, mid and short grass type of vegetation respectively, and can typically be found growing in the mixed prairie. It was the purpose of this study to determine any variations in the internal anatomy of these plants and to compare these variations with respect to species. Seeds of local source were planted in a greenhouse and, under ideal growing conditions, were allowed to germinate and develop for a period of three weeks. Samples of the roots, stems and leaves from each species were then collected and placed in F. A. A. solution. The samples were then sectioned, stained and mounted on slides. The diameter of the stem, the diameter of the root, the number and radial diameter of vascular bundles in the stem and root and the ratio of the diameter of the conductive tissue to diameter of total stem were the criteria used to measure the difference between the roots and stems of the three species. Criteria used to measure the difference in the anatomy of the leaf were the number, radial diameter and distance apart of the vascular bundles. Meristematic activity in the leaf was also used as a criterion for this study. Numerous measurements were made of each criterion, and photomicrographs were taken to aid in obtaining the resulting data. The results revealed the stem and. root of all species to consist of three tissue systems: (1) epidermal, (2) fundamental and (3) vascular. The three plants studied revealed only primary growth, but differences in the manner of primary growth were noted. The vascular bundles in side-oats grams and blue grama were scattered throughout the transection, but in big bluestems the vascular bundles were formed more or less in two circles, the smaller bundles near the periphery, and the larger bundles deeper within the stem. Since no vascular cylinder was formed in the stem, there was no distinction between the pith and cortex, but the central part of the root could be distinguished from the cortex by the presence of a pericycle. Big bluestem revealed the greatest stem diameter, root diameter, stem pith diameter and root conductive tissue diameter at this stage of growth. Blue grama showed the roost vascular bundles and also the greatest radial diameter of the vascular bundles in the stem. The ratio of the radial diameter of conducting tissue to diameter of total stem was greatest in side-oats grama, with big bluestem and blue grama being approximately the same. The leaf blades revealed many vascular bundles made up of two kinds of conducting tissues, the xylem and phloem. The leaves showed only primary growth, and large bulliform cells extending from one epidermis to the other were found between each vascular bundle. Sideoats grama contained the most bundles, but the diameter of the bundles was greatest in blue grama. Side-oats grama leaves had the greatest width, while big bluestem leaves had the greatest length. No meristematic activity was found at the base of the leaf blades.