OBSERVATIONS ON THE MICROBODIES IN THE GENUS TILLANDSIA (BROMELIACEAE)

Organelles morphologically similar to microbodies have been found in several tissues of atmospheric species of Tillandsia from different habitats. The presence of catalase was demonstrated by the DAB reaction thus confirming the microbody nature of these organelles. They are a feature of the Tillandsia species with normal photosynthetic carbon fixation and with CAM. Their size is consistently small. The nucleoid observed in the microbodies shows a characteristic morphology which has not been reported before within other plant microbodies. This nucleoid is composed of minute tubular structures, for which the authors here propose a three-dimensional arrangement.     

ROLE OF THE NITROGEN-FIXING BACTERIAL MICROFLORA IN THE EPIPHYTISM OF TILLANDSIA (BROMELIACEAE)

Nitrogen-fixing activity in the phyllosphere of 12 species of Tillandsia from different Mexican habitats was evaluated by the acetylene reduction assay, and nitrogen-fixing microorganisms were isolated and characterized. The leaves from eight of the 12 Tillandsia species examined exhibited nitrogenase activity in enrichment cultures. Among the microorganisms implicated—Agrobacterium, Bacillus, Erwinia, Pseudomonas, Rahnella, Vibrio, and Xanthomonas—only Bacillus megatherium reduced acetylene in pure culture. Our findings suggest that nitrogen fixation in the phyllosphere of the sampled epiphytes occurs under suitable conditions and that most of the bacteria involved are primarily soil and water inhabitants. The results also suggest a relationship between the composition of the nitrogen-fixing microbial communities grown on the leaf and the different development of the leaf area in Tillandsia due to the aerial components (wings) of the trichomes.     

ULTRASTRUCTURAL INVESTIGATIONS ON THE TWO-NUCLEATE POLLEN GRAIN OF TILLANDSIA CAPUT-MEDUSAE MORR. (BROMELIACEAE)

The fine structure of the pollen grain of Tillandsia caput-medusae Morr. (Bromeliaceae) prior to germination has been studied. The development, after the first mitosis, is here schematized in three stages which are in accordance with the main steps described in angiosperms. The ultrastructural modifications occurring in the generative and vegetative cells are discussed in view of their different destiny. The results obtained are compared with the data known about tropical orchids and epiphyteic plants like Tillandsia. The following differences have been observed: a large vacuole in the vegetative cell; rapid thinning of the wall between the generative and vegetative cells; great quantity of ribosomes and rough endoplasmic reticulum surrounding the vacuoles in the generative cell. The above-listed ultrastructural features may have a meaning, considering the peculiar environmental conditions in which the epiphytism of Tillandsia is achieved.     

MORPHOLOGICAL CHANGES ACCOMPANYING THE TRANSITION FROM JUVENILE (ATMOSPHERIC) TO ADULT (TANK) FORMS IN THE MEXICAN EPIPHYTE TILLANDSIA DEPPEANA (BROMELIACEAE)

Two distinct morphological forms characterize the ontogenetic development of the epiphytic bromeliad Tillandsia deppeana. Juveniles are characterized by a non-impounding rosette of small, linear leaves covered with elaborate trichomes possessing a 4 + 8 + 16 + 64 shield cell pattern. The broader transitional leaves, which form an impounding rosette prior to the initiation of true adult leaves, also possess trichomes with the 4 + 8 + 16 + 64 cell pattern. Adult individuals have large, broad leaves with overlapping, sheathing bases which impound water and debris. These leaves have trichomes with shields exhibiting a 4 + 8 + 32 cell pattern. Trichome density is fairly uniform in the juvenile leaves with trichomes covering 100% of leaf surfaces, whereas in the adult leaves density is high at the base and diminishes significantly toward the apex. Stomatal density of both juvenile and adult leaves increases from the base to the apex, although this is most pronounced in the adults. Stomata in the adults are also arranged in longitudinal series parallel and abaxial to parallel rows of mesophyll tissue. The results of this study indicate that juveniles of T. deppeana are more similar morphologically to adult atmospheric-type tillandsioid species than to the tank-forming adults into which they eventually develop.     

THE POSSIBLE ROLE OF A FIBROUS BODY IN THE GENERATIVE CELL OF THE POLLEN GRAIN OF TILLANDSIA CAPUT-MEDUSAE MORR. (BROMELIACEAE)

The occurrence of a fibrous body in the generative cell of the pollen grain of Tillandsia caputmedusae Morr. (Bromeliaceae) is pointed out and its possible role is indicated.     

CLADISTIC TESTS OF HYPOTHESES CONCERNING EVOLUTION OF XEROPHYTES AND MESOPHYTES WITHIN TILLANDSIA SUBG. PHYTARRHIZA (BROMELIACEAE)

Tillandsia L. Subg. Phytarrhiza (Visiani) Baker (Bromeliaceae) is a distinctive group of about 35 epiphytic species. These exhibit a range of habits from xeric to mesic. The evolutionary relationships of the contrasting adaptations need to be established here as well as in the subfamily as a whole. Relations between the subgenus and other tillandsioids are problematical and phylogenetic reconstruction of its member-species would be facilitated by identification of Phytarrhiza's relative (sister taxon) sharing the same most recent common ancestor with Phytarrhiza. This paper examines the two most likely sister taxa, Subg. Pseudo-Catopsis Baker and Subg. Diaphoranthema (Beer) Baker. Diaphoranthema is rejected as sister taxon. The accepted evolutionary tree, rooted by Pseudo-Catopsis, indicates that most habital evolutionary changes in Phytarrhiza have been between mesic and semi-mesic forms and from mesic to xeric forms. Methods developed for testing specific evolutionary hypotheses are broadly applicable.     

OLIGOTROPHIC TILLANDSIA CIRCINNATA SCHLECHT (BROMELIACEAE): AN ASSESSMENT OF ITS PATTERNS OF MINERAL ALLOCATION AND REPRODUCTION

Analyses of Tillandsia circinnata Schlecht specimens from nutrient-stressed and more fertile habitats in southern Florida confirmed earlier findings that its vegetative and reproductive vigor are enhanced as shoot tissue concentrations of P, K and Mg increase. Demands by this perennial herb for N, P and K are more pronounced than for B, Ca, Cu, Fe, Mg, Mn, Mo and Zn, primarily because N, P and K must be maintained at relatively high concentrations in vegetative tissues and are heavily expended during seed production. When most or all of this epiphyte's self-fertile flowers set fruit— a fairly common occurrence in most of the populations examined—asexual propagation by offshoot is subordinated to the sexual effort, especially if the specimen is growing in an unusually sterile habitat and has very limited mineral resources. Predictions implicit in r-K selection and related life history theory are consistent with the notion presented here that T. circinnata is following a pattern of nutrient use for reproductive purposes that represents a highly adaptive way to expend slowly accumulated mineral resources in stressful habitats represented by small, scattered, short-lived microsites. Specifically, it expends scarce mineral resources during the reproductive effort in a way that greatly enhances fecundity and vagility while minimizing the rate at which new microsites and reproducing individuals must be recruited. Reproduction and mineral use by T. circinnata is compared with that of T. utriculata, a semelparous epiphyte that shares many of the same forest habitats in southern Florida.     

CHROMOSOME NUMBERS IN BROMELIACEAE

Eighty-three chromosome counts are reported for 72 taxa of the Bromeliaceae. Fifty-eight of these counts are the first known chromosome number reports for their respective taxa. A model of chromosomal evolution in the Bromeliaceae (n = 25) is presented. The model is parsimonious and consistent with existing data on meiotic chromosome numbers within the family and in the closely related Velloziaceae (n = 9). Two hypothesized paleodiploids (n = 8 and n = 9) hybridized to form a tetraploid that in turn hybridized with the n = 8 lineage. The resultant n = 25 is the extant base number for the family. Two alternative hypotheses could explain the unique extant base number (n = 17) for Cryptanthus: 1) Cryptanthus represents the paleotetraploid level, i.e., prior to the second round of hybridization, or 2) the lower number represents the result of a more recent series of aneuploid reductions from n = 25. Given the existence of intergeneric hybrids involving Cryptanthus, aneuploid reduction is the more likely interpretation.     

POLLEN MORPHOLOGY AND EVOLUTION IN HEDYOTIS SUBGENUS EDRISIA (RUBIACEAE)

Primarily on the basis of aperture structure, 31 species of Hedyotis subg. Edrisia (Houstonia) are separable into 5 palynological groups. Group 1 is characterized by a simple os circumscribed by varying nexinous thickenings, groups 2–4 combine this os with a crassimarginate one to form a compound os, while group 5 is known only with the crassimarginate os. The first type is considered primitive, the compound os specialized and more advanced, and the third type reduced and highly advanced. Other characteristics of the pollen, including size and shape, aperture number, thickness of sexine and nexine, and reticulum, are discussed in relation to the apertures, and their probable primitive and advanced expressions are outlined. The data agree with the phyletic trends found in the sporophyte on the basis of results from morphology, chromosome number and size, and distribution, and they support and add to an earlier phylogenetic scheme proposed for the subgenus. The evidence from palynology also supports the treatment of Hedyotis and Houstonia as congeneric.     

A NUMERICAL ANALYSIS OF FLAVONOID VARIATION IN ARNICA SUBGENUS AUSTROMONTANA (ASTERACEAE)

Species of Arnica subgenus Austromontana produce a total of 23 leaf flavonoids, including simple and methylated flavone and flavonol glycosides as well as highly methylated flavone aglycones and a 6-hydroxylated flavone. Most of the taxa exhibit considerable interpopulational variability, with the number of compounds per population ranging from 2 to 14. Analysis of flavonoid variation in 113 populations representing all 9 species of the subgenus was carried out using cluster analysis, principal components analysis, and binary discriminant analysis. Results indicate the flavonoid profile of the very rare A. viscosa is the most distinctive in the subgenus. Although exhibiting considerable interpopulational variability, all populations of A. gracilis, a hybrid taxon, form a very distinct and cohesive group, supporting its recognition at the specific level. Additionally, chemical diversification from A. cordifolia has taken place largely in the Klamath region of Oregon and California. The range of variability exhibited by A. cordifolia is reflected in these Klamath region derivatives.     

MOVEMENT OF IAA IN SECTIONS FROM SPIDER FLOWER (CLEOME HASSLERIANA) STAMEN FILAMENTS

Movement of IAA in spider flower (Cleome hassleriana Chod.) stamen filaments was studied by placing 2-mm sections horizontally between donor agar blocks containing ¹⁴C-labeled IAA and plain agar receiver blocks and measuring radioactivity in the donor and receiver blocks and filament sections by scintillation counting after the desired transport time. Movement was strictly polar and basipetal at all stages of floral development, except in open flowers just before stamen abscission when the amounts moving acropetally and basipetally were equal. The amount of IAA moved depended upon the stage of development. As buds aged more IAA was moved, until the buds opened and the stamen filaments reached maximum elongation; then the amount of IAA moving basipetally dropped drastically. There was an insignificant amount of acropetal IAA movement except just before stamen abscission. This change in IAA movement is not due to a change in filament diameter. In time-course studies the amount of IAA moved basipetally increased with time up to 5 hr and then declined slightly. The amount of radioactivity retained by sections increased until 8 hr. The amount of IAA moved in tip sections was less than that in mid or base sections; however, this can be partially explained by differences in uptake area of these sections. The relationship of these results to the hypothesis that changes in IAA movement are important in the control of stamen filament elongation and abscission is discussed.     

GROWTH AND DIFFERENTIATION OF AXIAL AND LATERAL FILAMENTS IN BATRACHOSPERMUM SIRODOTII (RHODOPHYTA)1

Development of the vegetative gametophyte of Batrachospermum sirodotii Skuja was examined with light and both transmission and scanning electron microscopy. Patterns of wall growth were followed using the Calcofluor White ST pulse-chase method. Thallus structure was analysed in terms of the pattern of development of the apical, periaxial and pleuridial initials that generate the axial and whorled lateral filaments characteristic of Batrachospermum. Apical cells of axial filaments elongate initially by tip growth with the nucleus maintaining a distal position. Nuclear division is horizontal. One daughter nucleus migrates basipetally and a thin, convoluted annular septum and perforate-occluded pit connection are then formed. Elongating axial cells subsequently extend by wall deposition at the base of the cell. Periaxial cells are initiated laterally and elongate primarily by tip growth while the nucleus remains within the axial cell. The nucleus then migrates to the boundary between the initial and the axial cell, divides, and one daughter nucleus moves into the initial and the other back into the axial cell. A slightly irregular annular septum and simple-occluded pit connection are then formed. Pleuridial cell initials begin as terminal to subterminal protuberances on periaxial or pleuridial cells. They first extend by tip growth and later by bipolar band growth. The nucleus remains within the parent cell as the pleuridial initial expands and a narrow septal ring is formed between the two cells. It then migrates through the septal ring into the initial and divides transversely. One nucleus passes back into the parent cell and a thick, flat septum and perforate-occluded pit connection are formed. It is concluded that the potentially indeterminate axial filaments and the determinate lateral pleuridia represent distinct developmental types in Batrachospermum.     

LOCALIZATION OF MYOSIN FILAMENTS IN SMOOTH MUSCLE

Thick myosin filaments, in addition to actin filaments, were found in sections of glycerinated chicken gizzard smooth muscle when fixed at a pH below 6.6. The thick filaments were often grouped into bundles and run in the longitudinal axis of the smooth muscle cell. Each thick filament was surrounded by a number of thin filaments, giving the filament arrangement a rosette appearance in cross-section. The exact ratio of thick filaments to thin filaments could not be determined since most arrays were not so regular as those commonly found in striated muscle. Some rosettes had seven or eight thin filaments surrounding a single thick filament. Homogenates of smooth muscle of chicken gizzard also showed both thick and thin filaments when the isolation was carried out at a pH below 6.6, but only thin filaments were found at pH 7.4. No Z or M lines were observed in chicken gizzard muscle containing both thick and thin filaments. The lack of these organizing structures may allow smooth muscle myosin to disaggregate readily at pH 7.4.     

中国直突摇蚊属中直突摇蚊亚属记述(双翅目,摇蚊科)(英文)

记述中国直突摇蚊属中直突摇蚊亚属Orthocladius(Mesorthocladius)雄成虫3种,并对1新种O.(M.)tornatilis sp.nov.和中国1新纪录种O.(M.)vaillantiLangton & Cranston做详细描述。模式标本保存于南开大学生命科学学院摇蚊学研究室。圆钝中直突摇蚊,新种O.(M.)tornatilis sp.nov.(图1～3)雄成虫与本亚属其它已知种的区别如下:下附器背叶末端圆钝,抱器端节中部最宽,亚端背脊长而低。正模♂,吉林省长白山岳桦林,1994-04-30,扫网,王俊才采。词源:新种种名源自其下附器背叶圆钝。     

SUBGENUS MESORTHOCLADIUS (DIPTERA, CHIRONOMIDAE)FROM CHINA

记述中国直突摇蚊属中直突摇蚁亚属Orthocladius (Mesorthoccldius)雄成虫3种,并对l新种O.(M.)tornatilis sp.nov.和中国1新纪录种O.(M.)uaillanti Langton & Cranston做详细描述.模式标本保存于南开大学生命科学学院摇蚊学研究室.圆钝中直突摇蚊,新种O.(M.)tornatilis sp.nov.(图1～3)雄成虫与本亚属其它已知种的区别如下:下附器背叶末端圆钝,抱器端节中部最宽,业端背脊长而低.正模♂,吉林省长白山岳桦林,1994-04-30,扫网,王俊才采.词源:新种种名源自其下附器背叶圆钝.     

THE DOUBLE ARRAY OF FILAMENTS IN CROSS-STRIATED MUSCLE

The conditions under which one might expect to see the secondary filaments (if they exist) in longitudinal sections of striated muscle, are discussed. It is shown that these conditions were not satisfied in previously published works for the sections were too thick. When suitably thin sections are examined, the secondary filaments can be seen perfectly easily. It is also possible to see clearly other details of the structure, notably the cross-bridges between primary and secondary filaments, and the tapering of the primary filaments at their ends. The arrangement of the filaments and the changes associated with contraction and with stretch are identical to those already deduced from previous observations and described in terms of the interdigitating filament model in previous papers. There are therefore excellent grounds for believing that this model is correct. The alternative models which have been proposed appear to be incompatible both with the present observations and with much of the other available evidence.