Dominick J. Paolillo

Spermatogenesis in Polytrichum juniperinum : I. The origin of the apical body and the elongation of the nucleus.

SummarySpermatogenesis in Polytrichum juniperrinum includes a series of precise and coordinated morphogenetic movements among the organelles of the androcyte. The basal bodies, the underlying microtubules, and the multilayered structure (MLS) are positioned as an integrated unit at the periphery of the cell, and the nucleus migrates into contact with them. The shape of the nucleus begins to change, with the formation of an anterior projection, or beak. The mitochondrial sheath that has coalesced on the plastid divides to form the apical body, and elongation of the nucleus begins. The posterior basal body and one microtubule undergo lateral displacement from the rear forward, as elongation of the nucleus and the microtubules continues. The mitochondrial mass that is now the apical body grows rearward along the side of the elongated nucleus, and the two groups of microtubules in the MLS rearrange themselves. The lower elements of the MLS also participate in the morphogenetic rearrangement. By the time the nucleus has elongated once around the cell and the apical body has begun it s rearward growth, the lower elements of the MLS are found only beneath the anterior basal body. Subsequently these layers disappear from this location also.

Spermatogenesis in Polytrichum juniperinum : II. The mature sperm.

SummaryIn the mature sperm of Polytrichum, the nucleus contains only condensed chromatin. The apical body is as long as the posterior basal body, and the anterior basal body remains short. The microtubules that were part of the multilayered structure persist to form the filamentous appendage of the mature sperm. The cytoplasmic remnant contains the plastid and a few mitochondria that did not participate in the formation of the apical body.

Ultrastructural Features of Some Polytrichaceous Moss Leaves

The cells of the green lamellae on the adaxial surface of Poly- trichum and Atrichum leaves are typical chlorenchyma and their protoplasts are connected by few plasmodesma. The elongate parenchyma cells of the midrib are united by numerous protoplasmic connections that traverse the highly per- forated cross walls. All three parenchyma layers share this feature, and a single clearly differentiated layer of phloem-like cells was not recognized. The hydroids are mostly free from protoplasm and are separated from each other by thin, imperforate walls.

Photosynthesis and Respiration of Forest and Alpine Populations of Polytrichum juniperinum

Apparent photosynthesis was measured as a function of light intensity, temperature, and CO, concentration in alpine and forest populations of Polytrichum juniperinum Hedw. The forest population showed light saturation at lower light intensities, sustained apparent photosynthesis at higher temperatures, and showed a greater response to elevated CO, concentration than did the alpine population. The achlorophyllous margins of the leaves in the alpine plants are disproportionately large compared to those in forest plants. The differences in physiology and morphology can be interpreted as adaptations to the respective habitats of alpine and forest populations. The moss Polytrichum iuniperinum Hedw. is a widely distributed species in North America. It occupies diverse habitats ranging from the alpine zone, e.g. in the New England mountains, to fairly dry scrub oak forests on sandy soils. Species of such a wide range may consist of ecologically distinct races genetically adapted to their environments or they may possess wide tolerance limits that allow them to thrive under various environmental conditions. In phanerogams both conditions occur and are very well documented. In the bryophytes, studies on ecotypic differentiation are limited. Tallis (1959) reported that Rhacoamitrium lanuginosum has variable morphology according to the site variation, and that growth rates vary with altitude, being highest at 80 m and lowest at 720 m. Forman (1964) found that leaf morphology of Tetraphis pellucida varies with temperature, being wider relative to its length at lower temperatures. In another study (Forman, 1968) he found that there was an inverse correlation in caloric values of mosses with the altitudes at which they grow. Polytrichum juniperinum from the alpine zone of Mt. Washington gave the lowest value (3951 cal) of the alpine mosses studied. There are other reports indicating that some bryophytes are able to occupy diverse habitats because of their wide tolerances. For example, Rastorfer and Higinbotham (1968) showed that Bryum sandbergii has the capacity of net photosynthesis over a wide range of temperatures and light intensities. They explain its presence in all vegetation zones of the Pacific Northwest intermountain area on the basis of its wide tolerances. Szweykowski and Vogel (1966) found that populations of Geocalyx graveolens collected at two totally different 1 This study was performed at the Department of Botany, University of Illinois, Urbana. Support for the work was furnished in part by NSF GB-6520. We also acknowledge Dr. J. S. Boyer, who furnished the gas analyzer for our use. 2 Department of Botany, University of Illinois, Urbana, Illinois 61801. 3 Section of Genetics, Development, and Physiology, Cornell University, Ithaca, New York 14850. 4 Department of Botany, University of Vermont, Burlington, Vermont 05401. This content downloaded from 157.55.39.177 on Sat, 19 Nov 2016 04:38:54 UTC All use subject to http://about.jstor.org/terms 580 THE BRYOLOGIST [Volume 73 habitats showed no significant morphological differences when grown under the same environmental conditions. For this paper we studied two populations of P. juniperinum from contrasting habitats, measuring their patterns of CO2 exchange at various temperatures, light intensities, and carbon dioxide concentrations. In addition leaf morphology and turgor movements were studied to elucidate possible relationships with the environ-

Photosynthesis in Sporophytes of Polytrichum and Funaria

Photosynthesis was measured in excised sporophytes of Polytrichum and Funaria with an infrared gas analyzer. Net photosynthesis was recorded for Funaria, but photosynthesis beyond the compensation point was not demon- strable for Polytrichum. The gametophytes of both genera show net photo- synthesis, and the shapes of the light saturation curves for the gametophytes are similar to those obtained for their respective sporophytes. The distribution of dry weight within the sporophyte was followed during capsule development. In Polytrichum the weight of the seta decreases as the weight of the capsule increases. This is not the case in Funaria. These results establish the importance of seta reserves in the economy of the Polytrichum sporophyte during capsule expansion. Throughout its life, the moss sporophyte remains attached to the gametophyte. It is reasonable to assume that the gametophyte contributes organic compounds to the sporophyte during part or all of the sporophytes development. The presence of chloro- phyll throughout the young sporophyte (Bold, 1940), and especially in the capsule of the older sporophyte (Haberlandt, 1886), has prompted the question of whether or not sporophytic tissue can contribute to its own nutrition by photosynthesis. This paper is devoted to some preliminary attempts to answer this question by infrared gas analysis for the detection of photosynthesis. MATERIALS AND METHODS

The Effect of the Calyptra on Capsule Symmetry in Polytrichum juniperinum Hedw.

The splitting of the inner, sheathing layer of the calyptra on the sporophyte of Polytrichum juniperinum Hedw. leads to asymmetrical expansion and the development of a capsule that is bilaterally symmetrical and dorsiventral. When unexpanded sporophytes are cultured without the sheathing layer, expansion of the capsule is radially symmetrical. When unexpanded sporophytes are cultured with the sheathing layer intact, the sheath is split and capsule expansion is asymmetrical, as it is in field-grown plants. If capsules that have already become asymmetrical are grown in culture, they develop their later angularity as would be predicted on the basis of their asymmetry. It is concluded that capsule symmetry in Polytrichum is determined by the splitting of the calyptra and the asymmetrical expansion of the erect capsule. In contrast, xThis study was accomplished with the support of National Science Foundation grant GB-6520. 2 Department of Botany, University of Illinois, Urbana, Illinois 61801. This content downloaded from 207.46.13.37 on Wed, 03 Aug 2016 05:50:58 UTC All use subject to http://about.jstor.org/terms 328 THE BRYOLOGIST [Volume 71 capsule symmetry in Funaria is determined as the capsule expands in a horizontal position and is not a function of the splitting of the calyptra. Bopp (1954; 1957a, b) studied the relationship of the calyptra to capsule expansion in moss sporophytes, with special attention to Funaria. He concluded that the calyptra exerts a mechanical restraint on capsule expansion but does not determine the bilateral symmetry of the capsule. The present study is devoted to some observations on the importance of the calyptra in Polytrichum, especially with reference to the determination of capsule symmetry. MATERIALS AND METHODS Sods of Polytrichum juniperinum Hedw. were collected at Portland Arch, Indiana, on April 10, 1968. The collections contained sporophytes with unexpanded, partly expanded, and fully expanded capsules, so that the sequence of events during capsule expansion could be reconstructed. Plants with unexpanded and partly expanded capsules were excised from gametophytes, surface sterilized for two minutes with 5% Chlorox, and planted on Voths (1943) M5 solution solidified with 1% Difco Bacto-Agar. Unexpanded plants were cultured with and without the inner, sheathing layer of the calyptra. The culture tubes containing the plants were placed under 12 hours of daily illumination at 200 foot-candles under Sylvania Gro-lux fluorescent tubes, at 230C. Funaria hygrometrica Hedw. was obtained from the soil around potted plants in the Botany Greenhouse, on May 20, 1968, and from a border planting on the campus on May 18 and 28. Plants with capsules in various stages of development were examined, and the sequence of events in capsule expansion was reconstructed.