Rhizomatous Form Research Articles

Branching of tillers in some grasses

In investigations on the grass regeneration biology a special attention was paid to the formation of aerial tillers and branching pseudostolons in <i>Dactylis glomerata</i> L., <i>Festuca arundinacea</i> Schreb., <i>Festuca pratensis</i> Huds., <i>Festuca rubra</i> L., <i>Phleum pratense</i> L., <i>Lolium multiflorum</i> Lam., <i>Lolium perenne</i> L., <i>Phalaris arundinacea</i> L., <i>Arrhenatherum elatius</i> (L.) P. B., <i>Holcus lanatus</i> L., <i>Agropyron repens</i> (L.) P. B., <i>Avenastrum pubescens</i> (Huds) Opiz and <i>Agrostis alba</i> L. Aerial tillers, vegetative short ones and with partly elongated internodes as well as generative tillers formed in tufted and rhizomatous grasses. Parental raised tillers, on which aerial tillers developed, had the anatomical structure specific for grass stems. In tufted grasses, moreover, parental branching pseudostolons developed; in their cross section the arrangement of tissues specific for stolons was observed. They constituted the starting point for agglomerations of new plants rooting in soil, contrary to raised tillers. In some grass species, beside pendant roots, shorter roots grew at the base of aerial tillers; they surrounded with a ring the parent shoot in the node, thus reinforcing the connection of aerial tillers with the stem. An attention was paid to the favourable role of branching pseudostolons in the sward thickness formation. Conditions of the arrangement of tissues in the stem cross section, owing to which the rhizomatous form is developed, are discussed. The fertilization with compost or the covering with sand results in the formation of tillers resembling pseudorhizomes.

Interspecific Hybrids of Poa arachnifera × Poa secunda

Texas bluegrass (Poa arachnifera) and big bluegrass (P. secunda) are two extremely heat and drought tolerant species of Poa in the USA. They are distinct in their habitat, form of reproduction, and a number of phenotypic features. The development of a drought tolerant, rhizomatous form of Poa for the Southern Plains would provide a useful forage resource for the regions livestock industry. Interspecific hybrids between a locally collected P. arachnifera accession and a P. secunda cultivar (c.v. Sherman) to determine if hybrids and breeding advances were possible. Results indicated that barriers to hybridization were lim- ited and the 75 interspecific hybrids exhibited characteristics representa- tive of both parents. In addition, four androgenic haploids were generated which would provide useful material for genetic analysis of the Poa ge- nome and studies regarding inheritance of apomixis. The hybrids segre- gated for both monecious and a dioecious phenotypes and exhibited somatic chromosome numbers ranging from 54 to 72. As seedlings, the hybrids were robust and pollen fertility among the hybrids ranged from 0% to 90%. Twelve of the hybrids were seed fertile and 26 of the hybrids were pollen fertile. One dioecious hybrid was both pollen and seed fer- tile. Forage quality estimates indicate that the F1 hybrids will possess quality forage characteristics comparable to Lolium ssp., Bromus inermis, and Dactylis glomerata. The generation of fertile interspecific hybrids Bryan Kindiger is affiliated with the USDA-ARS, Grazinglands Research Labora-

Growth forms in the Alismatales. II. Two rhizomatous species: Sagittaria lancifolia and Butomus umbellatus

A comparative morphological study of Sagittaria lancifolia and Butomus umbellatus over their life cycles was undertaken. The two are very similar in adult form, characterized by apical bifurcation to form inflorescence and continuation growth as in other members of the Alismatidae.and also by rhizomatous growth with a subterminal apex. Embryo and seedling stages in S. lancifolia are comparable to other members of the Alismataceae previously studied. Rhizomatous form and bilateral symmetry are secondarily acquired during ontogeny. The inflorescence is leaf opposed and S. lancifolia is organizationally similar to other species of Alismataceae with upright vegetative axes. From this, a sympodial interpretation of the rhizome may be made. In contrast, the bilaterally symmetric growth form in Butomus is manifested from the start. The leaf-subtended inflorescence and other features of organization suggest that it cannot easily be compared with S. lancifolia or other members of Alismataceae. Here, a stronger case may be made for a monopodial construction. Axillary bud distributions support these conclusions. In addition, both species branch by a relatively precocious lateral bud associated topographically with the inflorescence.

BIOSYSTEMATIC STUDIES IN THE BOUTELOUA CURTIPENDULA COMPLEX. I. THE ANEUPLOID RHIZOMATOUS B. CURTIPENDULA OF TEXAS

Gould, F. W., and Z. J. Kapadia. (A. & M. College of Texas, College Station.) Biosystematic studies in the Bouteloua curtipendula complex. I. The aneuploid rhizomatous B. curtipendula of Texas. Amer. Jour. Bot. 49(8): 887–891. Illus. 1962.—Widespread throughout central U.S. is a rhizomatous form of B. curtipendula that basically is tetraploid (2n = 40). In the southwest the predominant type is a caespitose aneuploid with a high chromosome number (2n = ca. 80 to 2n = ca. 102). The present study has shown the presence of an extensive series of rhizomatous aneuploids in central Texas, with chromosome numbers ranging from 2n = 41 to 2n = 64. The distribution of these plants is centered about the region of overlap in the ranges of the 2 previously mentioned types. Available evidence indicates that the rhizomatous aneuploids have arisen through hybridization of the caespitose aneuploids and the rhizomatous tetraploids.