scholarly journals Plant Sexual Reproduction: Perhaps the current plant two-sex model should be replaced with three- and four-sex models?

2020 ◽  
Author(s):  
Scott Meissner
Keyword(s):  
Life Cycle ◽  
Sexual Reproduction ◽  
The Other ◽  
Male And Female ◽  
Sexual Determination ◽  
New Models ◽  
Plant Sexual Reproduction ◽  
Alternation Of Generations

The current plant two-sex model makes the assumption that there are only two sexual reproductive states: male and female. However, the application of this model to the plant alternation of generations requires the subtle redefinition of several common terms related to sexual reproduction, which also seems to obscure aspects of one or the other plant generation: For instance, the homosporous sporophytic plant is treated as being “asexual,” and the gametophytes of angiosperms treated like mere gametes. In contrast, the proposal is made that the sporophytes of homosporous plants are indeed sexual reproductive organisms, as are the gametophytes of heterosporous plants. This view requires the expansion of the number of sexual reproductive states we accept for plants, therefore a three-sex model for homosporous plants and a four-sex model for heterosporous plants are described and then contrasted with the current two-sex model. These new models allow the use of sexual reproductive terms in a manner largely similar to that seen in animals, and may better accommodate the plant alternation of generations life cycle than does the current plant two-sex model. These new three-sex and four-sex models may also help stimulate new lines of research, and examples of how they might alter our view of the flower, and may lead to new perspectives in terms of sexual determination, are presented. Thus it is suggested that plants have more than merely two sexual reproductive states, and that recognition of this may promote our study and understanding of plants.

scholarly journals Life cycle of Craspedacusta sowerbyi xinyangensis

2009 ◽  
Vol 55 (3) ◽  
pp. 227-234 ◽  
Author(s):  
Shanliang Xu ◽  
Danli Wang
Keyword(s):  
Life Cycle ◽  
Light Microscopy ◽  
Digital Camera ◽  
Zhejiang Province ◽  
The Other ◽  
Free Living ◽  
Cell Stage ◽  
Germ Layers ◽  
Male And Female ◽  
Gastrovascular Cavity

Abstract To explore the life cycle of Craspedacusta, the authors collected male and female specimens of the Craspedacusta sowerbyi xinyangensis in a small fire-fighting pond in Ningbo, Zhejiang Province in July, 2005 and 2006. The development of C. sowerbyi xinyangensis was studied from zygote to medusa by means of light microscopy and digital camera. The zygotes of C. sowerbyi xinyangensis are globular and smooth (90 - 105 μm diameter) and have an equal, total cleavage to the two-cell stage 15 min after fertilization. The embryos enter the four-cell stage after another 15 min and become multicellular embryos after 3h 15 min. At this stage the embryos have a diameter similar to fertilized eggs but have uneven surfaces that are distinct from the smooth surfaces of the uncleaved zygotes. Solid gastrulae are formed 7 h after fertilization. These are spherical planulae with short surface cilia that begin to swim in slow clockwise circles. After 12 h, they lose their cilia, cease swimming and become elongated planulae with one end larger than the other. Rod-like planulae, similar in thickness at both ends, are formed after an additional 7 h. After 4 days, the planulae develop into tiny polyps having two germ layers and a gastrovascular cavity. The polyp mouth is 50 - 62 µm in diameter, lacking tentacles but having nematocysts around the mouth. Planulae become mature polyps after 10 days (15 days after fertilization). Medusa buds (45 - 88 μm diameter) are formed by polyp budding, which soon become free-living medusae with 8 tentacles (380 - 620 μm diameters). Sometimes, the movement of frustules, which are formed by the polyps and similar to planulae in morphology can also be observed.

The life cycle ofAdelina cryptocercisp.nov., a coccidian parasite of the roachCryptocercus punctulatus

Parasitology ◽  
1937 ◽  
Vol 29 (3) ◽  
pp. 370-390 ◽  
Author(s):  
Evangeline Alderman Yarwood
Keyword(s):  
Life Cycle ◽  
Growth Period ◽  
The Other ◽  
Artificial Infection ◽  
Coccidian Parasite ◽  
Male And Female ◽  
Fat Bodies ◽  
Cryptocercus Punctulatus ◽  
Infection Experiments

1. The occurrence ofAdelina cryptocerciin the host,Cryptocercus punctulatus, and its probable means of natural transmission are discussed.2. Artificial infection experiments were carried out and furnished material for determination of succession of stages in the life cycle of the organism. The cycle is briefly as follows:(a) Mature cysts are ingested by the hosts with tissues of infected roaches. Sporozoites enter the host's tissues by passing through the midgut wall.(b) The first schizogony, in which merozoites are produced, ocurs in the fat-bodies between the sixteenth and twenty-fifth days after ingestion of cysts.(c) In the second schizogonial generation two types of schizogony produce merozoites and gametoblasts, respectively, between the twenty-fifth and twenty-ninth days following infection. There is evidence that both male and female gametoblasts are formed from a single schizont.(d) Male and female gametoblasts become associated during the growth period of the latter. When fully grown, they are surrounded by a membrane, the gametocyst. The male gametoblast undergoes 2 divisions, forming 4 microgametes, of which 1 fertilizes the macrogamete and the other 3 lie unused between the gametocyst and the first oocyst, which is formed shortly after fertilization. A second oocyst is formed before the first division of the synkaryon.(e) By repeated divisions of the synkaryon a multinucleate sporont is formed. This divides into uninucleate sporoblasts. Each sporoblast divides once, forming a sporocyst containing 2 sporozoites. Mature cysts occurred in experimentally infected roaches from 40 days onwards.3. The stages in the life cycle are described in detail.4. Evidence for zygotic meiosis inAdelina cryptocerciis presented.5. The effect of the parasite on the host is discussed.This investigation has been made at the suggestion of Dr Harold Kirby, Jr., and under his direction and that of Dr C. A. Kofoid. I wish to express here my grateful appreciation to both for their interest and many valuable suggestions and criticisms.

Studies on North Indian Volvocales. VI. On the life cycle and cytology of a new member of Phacotaceae, Dysmorphococcus sarmaii sp. nov.

1981 ◽  
Vol 59 (5) ◽  
pp. 726-734 ◽  
Author(s):  
R. Shyam
Keyword(s):  
New Species ◽  
Life Cycle ◽  
Chromosome Number ◽  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Morphological Variability ◽  
The Other ◽  
Laboratory Conditions ◽  
Contractile Vacuoles ◽  
A New Species

This paper deals with the morphology, reproduction, and cytology of a new species of Dysmorphococcus, viz., Dysmorphococcus sarmaii sp. nov. (Phacotaceae, Volvocales) from India. The lorica of this flagellate displays a remarkable morphological variability in nature as well as in culture under laboratory conditions. The alga is characterised by an anteriorly bilobed pentagonal lorica ornamentated with polygonal pores, a massive globose chloroplast that lacks a pyrenoid and almost completely occupys the protoplast, a prominent red stigma, two contractile vacuoles located anteriorly near the insertion of the flagella, and flagella that are equal to or a little longer than the length of the lorica. The pentagonal lorica of the present taxon differs remarkably from the broadly ovoid to globose lorica of D. variabilis Takeda, D. coccifer Korschikoff, and D. globosus Bold and Starr. The lorica of D. sarmaii is somewhat comparable in shape to D. punctatus Fott because of its bilobed anterior but differs from the latter in its ornamentation. The massive globose chloroplast lacking a pyrenoid in the present alga differs remarkably from the other species of this genus where the chloroplast possesses one or several pyrenoids. In addition, asexual reproduction, which is accomplished by division of the protoplast within the lorica, results in the production of 8–16 zoospores as compared with the earlier record of 2 and 4 zoospores in this genus. The alga is heterothallic and sexual reproduction, which was not known for the earlier described species of the genus Dysmorphococcus, takes place by isogametes produced 16–32(–64) per cell. The chromosome number recorded for D. sarmaii is n = 10.

scholarly journals CHROMOSOMAL ALTERNATION OF GENERATIONS IN NEREOCYSTIS LUETKEANA (MERTENS) POSTELS AND RUPRECHT

1961 ◽  
Vol 39 (7) ◽  
pp. 1711-1724 ◽  
Author(s):  
Lindley Kemp ◽  
Kathleen Cole
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Nuclear Division ◽  
Basal Cells ◽  
Cytological Examination ◽  
Male And Female ◽  
Nereocystis Luetkeana ◽  
History Of ◽  
Alternation Of Generations

A cytological examination of the life history of Nereocystis luetkeana has shown that an alternating chromosome number corresponds to the morphological alternation of generations. The first division sequence of the zoosporangial nucleus is meiotic and is followed by three, usually synchronous, mitotic divisions. Thirty-two zoospores are liberated from each sporangium, and their germination gives rise to male and female gametophytes. Genotypic determination of the sexes is believed to take place in Nereocystis. Mitosis in the gametophytes is regular and cytokinesis follows each nuclear division, producing few cells in the female and many cells in the male gametophytes. Thirty-one chromosomes can be counted at the mitotic prophase. Oogamy exists in Nereocystis and fertilization takes place after the egg is extruded from the oogonium. Nuclear division in the sporophyte appears to be preceded by division of the nucleolus. Colorless and non-septate rhizoids develop as elongations of the basal cells of the sporophyte.Temperature is an important factor in the development of various stages of the life cycle of Nereocystis grown in culture, particularly in the gametophytic stage where sexual structures are produced only at temperatures less than 10 °C and vegetative growth is most prolific at 14–18 °C.Some of the unfertilized eggs develop parthenogenetically and give rise to stunted, deformed plants with multinucleate cells.

Asexual reproduction of Pliocene solitary scleractinian coralTruncatoflabellum: a morphological and biometric study

2012 ◽  
Vol 86 (2) ◽  
pp. 268-272 ◽  
Author(s):  
Yuki Tokuda ◽  
Yoichi Ezaki
Keyword(s):  
Life Cycle ◽  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Size Distributions ◽  
Free Living ◽  
Transverse Division ◽  
Life Cycle Strategy ◽  
Life Mode ◽  
Alternation Of Generations

Truncatoflabellumhas been considered a free-living genus that exhibits both sexual and asexual phases; divided lower coralla (anthocauli) are specialized for asexual reproduction by transverse division through a decalcification process, whereas the upper coralla (anthocyathi) only undertake sexual reproduction, in a life-cycle strategy that includes a distinct alternation of generations. However, little evidence has been presented to support this idea of its life cycle. We elucidate the life mode ofTruncatoflabellumby identifying key fossil characters (e.g., multiple rejuvenations and decalcification records just beneath lateral spines) and statistically analyzing the size distributions of over 500 individual coralla. Results of those morphological and biometric analyses clearly indicate alternation of generations in the life cycle ofTruncatoflabellum.

Items’ Cross-Category Associations as a Confounding Factor in the Implicit Association Test

2001 ◽  
Vol 48 (2) ◽  
pp. 123-134 ◽  
Author(s):  
Melanie C. Steffens ◽  
Inga Plewe
Keyword(s):  
Implicit Association Test ◽  
Confounding Factor ◽  
Reaction Times ◽  
Association Test ◽  
The Other ◽  
Reaction Time Difference ◽  
Implicit Association ◽  
Male And Female ◽  
Research Activities ◽  
Degree Of Association

Abstract. The introduction of the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998 ) has stimulated numerous research activities. The IAT is supposed to measure the degree of association between concepts. Instances have to be assigned to these concepts by pressing appropriate keys as quickly as possible. The reaction time difference between certain conditions, termed the IAT effect, is used as an indicator of the degree of the concepts’ association. We tested the hypothesis that the degree of association between one concept (or category) and the instances of the other presented concept also influences reaction times. In our experiment, the instances in the target categories, male and female names, were kept constant. The adjectives in the evaluative categories were manipulated: Either the pleasant adjectives were female-associated and the unpleasant adjectives were male-associated, or vice versa. These stereotypic associations were indeed found to exert a substantial influence on the size of the IAT effect. This finding casts doubt on the assumption that the IAT effect may be interpreted as a pure measure of the degree of association between concepts.

Life cycle of Spirogyra decimina var. juergensii (Kütz.) O.V. Petlovany from Lake Baikal

2018 ◽  
pp. 1-7
Author(s):  
Ekaterina A. Volkova
Keyword(s):  
Life Cycle ◽  
Sexual Reproduction ◽  
Lake Baikal

Identification of Spirogyra species is based on the morphology of the fertile specimens. This work provides characteristics of growth and the time of reproduction of Spirogyra decimina var. juergensii in Lake Baikal and describes sexual reproduction and conditions for germination of new filaments of this species isolated from the lake.

LANGUAGE USE BETWEEN MALE AND FEMALE HOST IN HITAM PUTIH TALK SHOW

2018 ◽  
Vol 14 (2) ◽  
Author(s):  
Nurmaliana Sari ◽  
Sumarsih Sumarsih ◽  
Busmin Gurning
Keyword(s):  
Language Use ◽  
The Other ◽  
Male And Female ◽  
Talk Show ◽  
Dominant Language ◽  
Other Hand ◽  
Domestic Activities ◽  
Female Host ◽  
Negative Connotation ◽  
Descriptive Qualitative

This study discusses about language use occurred by male and female host in Hitam Putih talk show. The method of this research is descriptive qualitative. The subjects of this study are male and female host in Hitam Putih talk show. The data are the utterances produced by male and female host in Hitam Putih talk show. This research focuses on the show broadcasted on October 2016 by taking 4 videos randomly. The objective of this study is to describe kinds of the language use uttered by male and female host in Hitam Putih talk show. The findings showed that the kinds of language use consist of 6 parts. The dominant language use uttered by male host is expletive, because male’s utterances are frequently stated in a negative connotation. On the other hand, female host utterances are found in specialized vocabulary as the most dominant because female host has more interest in talking family affairs, such as the education of children, clothes, cooking, and fashion, etc. Women also tended to talk about one thing related to the home and domestic activities. However, the representation of language use uttered by male and female are deficit, dominance and different. Keywords: Language Use, Gender, Talk Show

BIOCHEMICAL STUDIES ON SOCKEYE SALMON DURING SPAWNING MIGRATION: IV. THE NON-PROTEIN NITROGENOUS CONSTITUENTS OF THE MUSCLE

1958 ◽  
Vol 36 (8) ◽  
pp. 833-838 ◽  
Author(s):  
J. D. Wood
Keyword(s):  
Sockeye Salmon ◽  
The Other ◽  
Spawning Migration ◽  
Female Fish ◽  
Male And Female ◽  
Low Level ◽  
Early Stages ◽  
Biochemical Studies

The non-protein nitrogenous constituents of muscle of migrating sockeye salmon were investigated. These constituents were found to be the same in both male and female fish and were present in approximately the same amounts in both sexes. The histidine content of the muscle in all fish decreased to one fifth of the original value during the early stages of the migratory journey and remained at the low level thereafter. Some of the other constituents changed to a smaller extent, usually increasing in the later stages of the migration. This was especially noticeable in female fish. However, the increase in the concentration of these constituents in the muscle was due to a decrease in the amount of muscle in the fish rather than to an increase in the amounts of the compounds themselves.

The five‐factor personality model in applied settings

1994 ◽  
Vol 8 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Itzhak Montag ◽  
Joseph Levin
Keyword(s):  
Factor Analysis ◽  
Personality Inventory ◽  
The Other ◽  
Factor Solution ◽  
Male And Female ◽  
Neo Personality Inventory ◽  
Clear Cut ◽  
Five Factors ◽  
Male Subjects ◽  
Female Subjects

Two studies of the Revised NEO‐Personality Inventory (NEO‐PI‐R) conducted on two different applicant samples (one consisting of 539 female subjects and the other consisting of 396 male subjects) are reported. Factor analysis of the female sample yielded a five‐factor solution, highly congruent with the factors presented by Costa, McCrae and Dye (1991). Results of the male data were less clear‐cut, yielding four to five factors which were moderately congruent with the American data. The combined male and female sample showed again high congruence coefficients. Various minor deviations in the location of the facet variables are discussed.

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