Experimental and Analytical Studies of Pteridophytes

Tepper, H. B. (State U. Coll. of Forestry, Syracuse, New York.) Dimensional and zonational variation in dormant shoot apices of Pinus ponderosa. Amer. Jour. Bot. 50(6): 589–596. Illus. 1963.—The dimensions and zonation of the apices of the dormant leader and terminal branches in 8 ponderosa pine trees are compared. Apices in upper positions in the crown tend to have larger diameters than those in lower positions. While no consistent trend in the variation of the height of the shoot apex could be demonstrated, the height/diameter (H/D) ratio of the apex increases in progressively lower positions in the crown. Correlation analysis of the pooled data from all trees indicates there is no correlation between height and diameter, but that there is a significant correlation between H/D ratio and diameter of the apex. The H/D ratio of apices of small diameter is larger than that in those of large diameter. While the cytohistological zonation of apices in all positions in the crown is similar, apices of largo diameter have a more extensive distal zone, rib meristem zone and peripheral zone than those of small diameter.

Dimensional and Zonational Variation in Dormant Shoot Apices of Pinus Ponderosa

Tepper

1963

Experimental Control of the Shoot System in Sporelings of Pteridium Aquilinum

Gottlieb

Steeves

1965

The shoot system of Pteridium develops from a simple, upright sporeling type through a rhizomatous leaf-bearing form, into a complex system with rapidly growing, leafless long shoots and slowly growing, leafy lateral branches or short shoots. Transitional stages are available in sporeling material and ontogeny may be controlled by specific carbohydrate levels. At concentrations of sucrose below 2% a rhizomatous sporeling plant may be maintained indefinitely in the leaf-bearing state. At 2-8% sucrose, the short shoot habit becomes established, and at 4-8% it may be reliably stabilized. If concentrations up to 5 mg/Iiter of kinetin are added to cultures of

Shoot Organization in the Filicales: The Promeristem

McAlpin

White

1974

The classical pteridophyte apical cell theory of meristem organization is not flexible or realistic enough to encompass the variation encountered in a comprehensive anatomical survey of fern meristems. The meristems of 28 taxa of ferns (both eu‐ and leptosporangiate) were studied. This analysis has led to the formulation of the concept of a promeristem composed of two zones: the surface and subsurface initials. This concept is flexible and sufficient to describe the variation encountered in the ferns as a group. No differences in promeristem organization were observed in plants with various rhizome morphology (e.g., upright and radial; prostrate and dorsiventral). Marking experiments, performed on living surface cells of fern promeristems, correlate with anatomical observations of division planes in the promeristem and indicate that the central, surface initials are not quiescent. Feulgen determinations indicate that Nephrolepis stolons have no endomitotically polyploid cells in the promeristem. Additional work is needed before a generalization can be made concerning ploidy levels in a more typical fern apex. Ferns, in general, have a zoned promeristem which is parallel to the zonation described for higher vascular plants.