摘要:

Hedyotis caeruleais a perennial, spring‐flowering herb native to eastern North America with distylous flowers that differ in a number of morphological and physiological traits. However, the pin and thrum morphs produce the same numbers of buds, flowers, and fruits per plant, although it is possible that differences in these may occur in some populations at certain times of the flowering period. The two morphs are self‐incompatible and cross‐compatible. Most populations contained an excess of pins over thrums (anisoplethy); less commonly pins and thrums were equally represented (isoplethy). Populations change from anisoplethy to isoplethy and in the reverse direction. The spatial distribution of pin and thrum flowers in populations was random in some populations but non‐random in others. There is some indication that the two morphs in some populations have somewhat different flowering periods. Pollinators seem to be chiefly bombyliid flies and perhaps thrips, but insects were rarely observed visiting flowers. In some populations, the two morphs produced equal numbers of pollen grains per flower; in others they did not. The average pollen viability varied, but on the average there was a moderate level of pollen sterility. High numbers of pollen grains remained in dehisced anthers, probably as a result of low pollinator activity. However, between 5% and 9% of the pollen produced participated in pollination. Stigmas of most pin flowers received more pin pollen grains than thrum pollen grains; on stigmas of thrum flowers pin pollen grains outnumbered thrum pollen grains. Thus, compatible pollen flow from pins to thrums was greater than in the reverse direction. Anisoplethic and isoplethic populations had the same pollen flow patterns. A plant‐by‐plant examination of stigmas indicated that many stigmas bore few or no pollen grains. Seed production of the two morphs was equal. Despite the inequities in pollen flow patterns, the widespread and occasionally weedy nature ofH. caeruleasuggests that its breeding system must be viewed as a successful one.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07627.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Reproductive physiology inSyringodium filiformeKütz. is controlled primarily by temperature under day lengths ranging from 12 hr to continuous light. Texas plants can be induced to flower at temperatures ranging from 20 to 24 C, but southern Gulf of Mexico and Caribbean plants are most readily induced at 23–24 C. Texas plants proceed to anthesis at temperatures above 22 C, but St. Croix plants require higher temperatures, above 25 C, for emergence of flowers from the bracts. Flowers induced under continuous light proceed to anthesis under day lengths shortened to 11 hr, but further floral induction is inhibited even under inductive temperatures. In natural seagrass beds, flowering occurs primarily under lengthening day lengths and warming temperatures that follow winter minima, but inflorescences may occur at other times of the year if temperatures permit.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07628.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

An integrated microscopic (light and electron microscopy) and macroscopic investigation of chambered pith development was made ofPhytolacca americanaL. Terminal internodes have a solid pith cylinder in contrast to the alternating diaphragms and chambers occurring in subjacent pith. Macroscopically, chambers and diaphragms of any one internode are of equal size. Microscopically, diaphragms vary in height within an internode (from 1–6 cells high). Nevertheless, all diaphragms become thicker circumferentially (5–12 cells high) and connect with long files of intact peripheral pith cells. Diaphragm cells have a large centrally positioned vacuole with a thin, parietal layer of cytoplasm; nuclei, mitochondria, endoplasmic reticulum, and unidentified organelles differentiate in the cytoplasm of diaphragm cells. Although schizogenous activity has most often been implicated as the mechanism by which chambered pith develops in vegetative organs of angiosperms, the results of this study show that cavities in pokeweed result from both schizogenous and lysigenous mechanisms. Schizogeny is suggested by the fact that central pith cells of terminal internodes are longer and thinner walled than peripheral pith cells arranged in vertical files, thus indicating elongation of cells as a possible result of internode elongation. The precise developmental pattern and arrangement of chambers and diaphragms also suggest schizogenous processes. Lysigenous or enzymatic activity is indicated by the fact that cavities are bounded by broken cells, and wall fragments and organelles are often found within enlarging cavities. Chamber formation occurs continuously acropetally and centrifugally in the central pith. A comparison of diaphragms is made withLiriodendron tulipiferaandJuglans nigrain an attempt to resolve differences in structure and terminology regarding the differentiation of chambered and diaphragmed pith.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07629.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

A “double‐blepharoplast” originates de novo in the spermatogenous cell ofGinkgo bilobaL. Initially, the double‐blepharoplast consists of two opposing hemispherical bodies comprised of densely staining material. The two blepharoplasts seemingly are pushed apart by the formation of densely packed fibrils which are oriented perpendicular to the distal, rounded edges of the two future blepharoplasts. As the latter move apart, each one develops lightly staining channels which are often organized in a hub and spoke configuration (procentrioles). Microtubules extend from the blepharoplasts as the latter move to their final position in the cell, and centrioles (probasal bodies) become organized at the periphery of each blepharoplast. Two large “osmiophilic globules,” conspicuous entities close to the nucleus of the mature spermatogenous cell, arise de novo. A fibrillogranular body in the cytoplasm, always closely associated with the nucleus, also arises de novo.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07630.x

出版商:Wiley    

年代:1980

数据来源: WILEY

摘要:

Silicified leaf‐sheath fragments ofEquisetumsp. are described from Late Tertiary strata in west‐central Nebraska. The close affinity of these fossils to the subgenusHippochaetaeis supported by the presence of sunken stomata arranged in two regular rows on each leaf‐sheath segment. This is the first report of the genusEquisetumfrom the late Tertiary Ash Hollow Formation of central North America.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07631.x

出版商:Wiley    

年代:1980

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07632.x

出版商:Wiley    

年代:1980

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07633.x

出版商:Wiley    

年代:1980

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1980.tb07616.x

出版商:Wiley    

年代:1980

数据来源: WILEY