Potted fireweed plants, Epilobium angustifolium L., were grown both from seed and root segments and subjected to early, late, and continuous defoliation and to apical excision during a single growing season. Seed-grown plants and root regenerates compensated completely for the early defoliation treatment and did not differ significantly from controls with respect to the dry weight of any yield component. Late defoliation significantly reduced the weight of flowers and fruit in seed-grown plants and root regenerates, and the annual increment of root weight in root regenerates. Continuous defoliation (early + late) significantly reduced the weight of flowers in seed-grown plants and the weight of both flowers and fruit in root regenerates. Apical excision significantly increased the total weight, shoot weight, and root weight of seed-grown plants but did not significantly affect any yield component in root regenerates. Reproductive allocation, defined as the percentage of total biomass in flowers and fruit, was significantly reduced in both seed-grown plants and root regenerates by the late and continuous defoliation treatments.
{"title":"Biomass Allocation in Fireweed Epilobium angustifolium L. (Onagraceae) in Response to Simulated Defoliation","authors":"J. Michaud","doi":"10.1086/337881","DOIUrl":"https://doi.org/10.1086/337881","url":null,"abstract":"Potted fireweed plants, Epilobium angustifolium L., were grown both from seed and root segments and subjected to early, late, and continuous defoliation and to apical excision during a single growing season. Seed-grown plants and root regenerates compensated completely for the early defoliation treatment and did not differ significantly from controls with respect to the dry weight of any yield component. Late defoliation significantly reduced the weight of flowers and fruit in seed-grown plants and root regenerates, and the annual increment of root weight in root regenerates. Continuous defoliation (early + late) significantly reduced the weight of flowers in seed-grown plants and the weight of both flowers and fruit in root regenerates. Apical excision significantly increased the total weight, shoot weight, and root weight of seed-grown plants but did not significantly affect any yield component in root regenerates. Reproductive allocation, defined as the percentage of total biomass in flowers and fruit, was significantly reduced in both seed-grown plants and root regenerates by the late and continuous defoliation treatments.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"208 - 213"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A sexual, yellow-anthered, tetraploid (2n = 4X = 40) biotype of dallisgrass, Paspalum dilatatum Poir., was crossed with an apomictic, purple-anthered, hexaploid (2n = 6X = 60) dallisgrass biotype from Uruguay to determine their cytological relationship and to establish the genomic composition of the hexaploid Uruguayan biotype. Forty-one intraspecific F1 hybrids were produced and 20 were studied cytologically. Nineteen plants had 50 chromosomes and one was aneuploid with 47 chromosomes. During metaphase I, the mean chromosome associations for 50-chromosome hybrids were 10.31I, 19.83II, 0.003III, and 0.003IV. The mean meiotic associations of the aneuploid hybrid were 7.12I and 19.94II. Most bivalents occurred as rings. These findings indicate that the biotypes have two homologous genomes. Based on the genome formula (IIJJ) of the yellow-anthered biotype, the 60-chromosome Uruguayan biotype has both the I and J genomes plus a third genome and its formula may be expressed as IIJJXX, where X is the third genome. The formula of the F1 hybrids is IIJJX. The chromosome number (2n = 5X = 50) and meiotic pairing behavior (20II + 10I) of these hybrids are similar to those of apomictic common dallisgrass. These results suggest that they may have the same genomic formula, but similarity of the X genomes in the Uruguayan and common biotypes has not been proven. If they are similar, apomictic common dallisgrass probably originated from a natural cross between the sexual yellow-anthered biotype or a closely related sexual tetraploid relative and the apomictic, hexaploid Uruguayan biotype.
{"title":"Genome Relationships between Tetraploid and Hexaploid Biotypes of Dallisgrass, Paspalum dilatatum","authors":"B. Burson","doi":"10.1086/337883","DOIUrl":"https://doi.org/10.1086/337883","url":null,"abstract":"A sexual, yellow-anthered, tetraploid (2n = 4X = 40) biotype of dallisgrass, Paspalum dilatatum Poir., was crossed with an apomictic, purple-anthered, hexaploid (2n = 6X = 60) dallisgrass biotype from Uruguay to determine their cytological relationship and to establish the genomic composition of the hexaploid Uruguayan biotype. Forty-one intraspecific F1 hybrids were produced and 20 were studied cytologically. Nineteen plants had 50 chromosomes and one was aneuploid with 47 chromosomes. During metaphase I, the mean chromosome associations for 50-chromosome hybrids were 10.31I, 19.83II, 0.003III, and 0.003IV. The mean meiotic associations of the aneuploid hybrid were 7.12I and 19.94II. Most bivalents occurred as rings. These findings indicate that the biotypes have two homologous genomes. Based on the genome formula (IIJJ) of the yellow-anthered biotype, the 60-chromosome Uruguayan biotype has both the I and J genomes plus a third genome and its formula may be expressed as IIJJXX, where X is the third genome. The formula of the F1 hybrids is IIJJX. The chromosome number (2n = 5X = 50) and meiotic pairing behavior (20II + 10I) of these hybrids are similar to those of apomictic common dallisgrass. These results suggest that they may have the same genomic formula, but similarity of the X genomes in the Uruguayan and common biotypes has not been proven. If they are similar, apomictic common dallisgrass probably originated from a natural cross between the sexual yellow-anthered biotype or a closely related sexual tetraploid relative and the apomictic, hexaploid Uruguayan biotype.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"219 - 223"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/337883","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small permineralized monocotyledonous rhizomes and aerial stems from the Middle Eocene Princeton chert in British Columbia are described and named Soleredera rhizomorpha gen. et sp. nov. Rhizomes are up to 1.3 cm wide, have a narrow cortex without vascular bundles, and show a central cylinder composed of three or more irregular cycles of primary vascular bundles embedded in compact thick-walled ground tissue. The central cylinder surrounds a hollow or sometimes solid pith and is separated from the cortex by an endodermoid layer. Rhizome vascular bundles are collateral or amphivasal and lack a fibrous bundle sheath. Metaxylem consists of angular tracheids 9-42 μm wide with scalariform, transitional, opposite, or mostly alternate intervascular pitting. Pit apertures are lined with vesture-like projections. Attached to the rhizomes are lateral branches 2-3 mm wide and roots 0.5-1.5 mm wide. Aerial stems differ from the rhizomes in having two to three cycles of collateral bundles, tracheids with mostly scalariform lateral wall pitting, and ground tissue with relatively large intercellular spaces. Also, the aerial stems lack an endodermoid layer, cortex, and roots. Anatomical comparisons to extant monocotyledons show that the stems closely resemble several lilialean families (Liliaceae, Iridaceae), but lack of leaves and floral parts of Soleredera precludes its assignment to a family. Nevertheless, these vegetative remains are the first anatomically preserved lilialean megafossils from Middle Eocene deposits in North America to be described. Discovery of Soleredera adds to our knowledge of vegetative anatomy, morphology, and diversity of monocotyledons in the early Tertiary of western North America.
本文描述了不列颠哥伦比亚省中始新世普林斯顿花岗岩的小型过矿物化单子叶根茎和气生茎，并将其命名为Soleredera rhizomorpha gen. et sp. 11 .根茎宽达1.3厘米，皮质狭窄，没有维管束，中心圆柱体由三个或更多不规则周期的初级维管束嵌入致密的厚壁地面组织中。中央柱围绕着中空或实心的髓，由内胚层与皮层隔开。根状茎维管束为侧支或两维管状，缺乏纤维束鞘。内质部由9 ~ 42 μm宽的角管胞组成，管胞间有鳞状、过渡性、对生或互生的孔蚀。坑孔排列着类似礼服的投影。与根茎相连的侧枝宽2-3毫米，根宽0.5-1.5毫米。气生茎与根状茎的不同之处在于具有2到3轮的侧枝，管胞具大部分鳞片状的侧壁凹陷，和具有相对大的细胞间隙的地面组织。此外，气生茎缺乏内胚层、皮层和根。与现存单子叶植物的解剖比较表明，其茎与百合科、鸢尾科的几个百合科非常相似，但缺乏叶片和花的部分，使其无法归属于百合科。然而，这些植物性遗骸是北美洲始新世中期沉积物中第一个解剖保存的百合花巨型化石。Soleredera的发现增加了我们对北美西部第三纪早期单子叶植物的营养解剖学、形态学和多样性的认识。
{"title":"Soleredera rhizomorpha gen. et sp. nov., a Permineralized Monocotyledon from the Middle Eocene Princeton Chert of British Columbia, Canada","authors":"Diane M. Erwin, R. Stockey","doi":"10.1086/337885","DOIUrl":"https://doi.org/10.1086/337885","url":null,"abstract":"Small permineralized monocotyledonous rhizomes and aerial stems from the Middle Eocene Princeton chert in British Columbia are described and named Soleredera rhizomorpha gen. et sp. nov. Rhizomes are up to 1.3 cm wide, have a narrow cortex without vascular bundles, and show a central cylinder composed of three or more irregular cycles of primary vascular bundles embedded in compact thick-walled ground tissue. The central cylinder surrounds a hollow or sometimes solid pith and is separated from the cortex by an endodermoid layer. Rhizome vascular bundles are collateral or amphivasal and lack a fibrous bundle sheath. Metaxylem consists of angular tracheids 9-42 μm wide with scalariform, transitional, opposite, or mostly alternate intervascular pitting. Pit apertures are lined with vesture-like projections. Attached to the rhizomes are lateral branches 2-3 mm wide and roots 0.5-1.5 mm wide. Aerial stems differ from the rhizomes in having two to three cycles of collateral bundles, tracheids with mostly scalariform lateral wall pitting, and ground tissue with relatively large intercellular spaces. Also, the aerial stems lack an endodermoid layer, cortex, and roots. Anatomical comparisons to extant monocotyledons show that the stems closely resemble several lilialean families (Liliaceae, Iridaceae), but lack of leaves and floral parts of Soleredera precludes its assignment to a family. Nevertheless, these vegetative remains are the first anatomically preserved lilialean megafossils from Middle Eocene deposits in North America to be described. Discovery of Soleredera adds to our knowledge of vegetative anatomy, morphology, and diversity of monocotyledons in the early Tertiary of western North America.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"231 - 247"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/337885","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The species-specific chemical messenger, antheridiogen, mediates the differentiation of male gametophytes in the fern Ceratopteris richardii Brongn. For different genetic strains, characteristic frequencies of sexual gametophytes primarily depend upon the relative sensitivity of gametophytes to antheridiogen. Exogenous supplementation with abscisic acid inhibits this antheridiogen response in sensitive strains of C. richardii. To further clarify the basis of the antheridiogen sensitivity, we examined the responses of gametophytes to antheridiogen and abscisic acid in three strains with distinct sensitivities to these agents. Depending upon strain and sexual phenotype, abscisic acid inhibited male morphology, inhibited antheridia production, and reduced gametophytic growth. An inverse relationship of antheridiogen and abscisic acid sensitivity indicated that endogenous levels of abscisic acid may contribute to the antheridiogen sensitivity of individual gametophytes. Even though abscisic acid contents of spores and young gametophytes did not correspond to the relative sensitivities of strains to antheridiogen, concentrations in mature spores and sexually indeterminate gametophytes were sufficient to contribute substantially to a constraint of antheridiogen responses.
{"title":"Control of Sexual Development in Gametophytes of Ceratopteris richardii: Antheridiogen and Abscisic Acid","authors":"T. Warne, L. G. Hickok","doi":"10.1086/337874","DOIUrl":"https://doi.org/10.1086/337874","url":null,"abstract":"The species-specific chemical messenger, antheridiogen, mediates the differentiation of male gametophytes in the fern Ceratopteris richardii Brongn. For different genetic strains, characteristic frequencies of sexual gametophytes primarily depend upon the relative sensitivity of gametophytes to antheridiogen. Exogenous supplementation with abscisic acid inhibits this antheridiogen response in sensitive strains of C. richardii. To further clarify the basis of the antheridiogen sensitivity, we examined the responses of gametophytes to antheridiogen and abscisic acid in three strains with distinct sensitivities to these agents. Depending upon strain and sexual phenotype, abscisic acid inhibited male morphology, inhibited antheridia production, and reduced gametophytic growth. An inverse relationship of antheridiogen and abscisic acid sensitivity indicated that endogenous levels of abscisic acid may contribute to the antheridiogen sensitivity of individual gametophytes. Even though abscisic acid contents of spores and young gametophytes did not correspond to the relative sensitivities of strains to antheridiogen, concentrations in mature spores and sexually indeterminate gametophytes were sufficient to contribute substantially to a constraint of antheridiogen responses.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"148 - 153"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Diverse native morphotypes of apomictic buffelgrass (Pennisetum ciliare [L.] Link [Cenchrus ciliaris L.]) were investigated cytologically to determine the sources of variation and to establish relationships among widely different natural accessions. The primary objectives were to determine mode of reproduction of accessions and hybrid progenies through embryo sac studies and to assess the potential of the material for use as germplasm in a breeding program. Although most native buffelgrass ecotypes are obligate apomicts, reproductive studies showed evidence for sexual reproduction (facultative apomixis) in each of five accessions chosen for a hybridization study. A fully differentiated single sexual embryo sac was observed in 7% of the ovules from two accessions, each of which also had one facultative ovule. Cytological studies on five of the most diverse types and their F1 hybrids with a sexual buffelgrass clone (B-1s) showed very similar chromosome pairing relationships at metaphase I of parents and their progenies. These results demonstrate a close relationship between types and indicate that they represent a primary gene pool for breeding purposes. The extreme morphological diversity present in the types is explained by the limited sexual reproduction. Highly apomictic divergent morphotypes could colonize large areas and easily be mistaken for different species.
{"title":"Cytological and Morphological Diversity of Native Apomictic Buffelgrass, Pennisetum ciliare (L.) Link","authors":"K. Hignight, E. C. Bashaw, M. Hussey","doi":"10.1086/337882","DOIUrl":"https://doi.org/10.1086/337882","url":null,"abstract":"Diverse native morphotypes of apomictic buffelgrass (Pennisetum ciliare [L.] Link [Cenchrus ciliaris L.]) were investigated cytologically to determine the sources of variation and to establish relationships among widely different natural accessions. The primary objectives were to determine mode of reproduction of accessions and hybrid progenies through embryo sac studies and to assess the potential of the material for use as germplasm in a breeding program. Although most native buffelgrass ecotypes are obligate apomicts, reproductive studies showed evidence for sexual reproduction (facultative apomixis) in each of five accessions chosen for a hybridization study. A fully differentiated single sexual embryo sac was observed in 7% of the ovules from two accessions, each of which also had one facultative ovule. Cytological studies on five of the most diverse types and their F1 hybrids with a sexual buffelgrass clone (B-1s) showed very similar chromosome pairing relationships at metaphase I of parents and their progenies. These results demonstrate a close relationship between types and indicate that they represent a primary gene pool for breeding purposes. The extreme morphological diversity present in the types is explained by the limited sexual reproduction. Highly apomictic divergent morphotypes could colonize large areas and easily be mistaken for different species.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"214 - 218"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/337882","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In spring prior to budbreak, 15 seedlings, from each of five broadleaf tree species that had been exposed to high light regime during the previous summer, were placed under a dense forest canopy while 15 others were left in the open. Leaf absorbance in the 400-1,100 nm waveband was measured for each seedling (two leaves per seedling) following full leaf development (early June) and prior to leaf senescence (late July). The same leaves were measured at both times. In early June, the highly shade tolerant sugar maple (Acer saccharum) already showed significant differences in leaf absorbance of its shaded and sunlit leaves. In this species, light conditions at time of budbreak seem to have greater effects on leaf physiology than light conditions prevailing during formation of leaf primordia. Leaves of mid-tolerant bur oak (Quercus macrocarpa), white ash (Fraxinus americana), and yellow birch (Betula alleghaniensis) responded less quickly to shade, with absorbance differences appearing later in summer. As for the intolerant butternut (Juglans cinerea), the small differences in absorbance between shaded and sunlit leaves in late July indicated a lower response to shade in its seedling leaves. These results indicated that spectral analysis might be a more appropriate tool to differentiate true sun from shade leaves than the morphological parameters commonly used.
{"title":"Plasticity of Leaf Absorbance in some Broadleaf Tree Seedlings","authors":"C. St-Jacques, M. Labrecque, P. Bellefleur","doi":"10.1086/337879","DOIUrl":"https://doi.org/10.1086/337879","url":null,"abstract":"In spring prior to budbreak, 15 seedlings, from each of five broadleaf tree species that had been exposed to high light regime during the previous summer, were placed under a dense forest canopy while 15 others were left in the open. Leaf absorbance in the 400-1,100 nm waveband was measured for each seedling (two leaves per seedling) following full leaf development (early June) and prior to leaf senescence (late July). The same leaves were measured at both times. In early June, the highly shade tolerant sugar maple (Acer saccharum) already showed significant differences in leaf absorbance of its shaded and sunlit leaves. In this species, light conditions at time of budbreak seem to have greater effects on leaf physiology than light conditions prevailing during formation of leaf primordia. Leaves of mid-tolerant bur oak (Quercus macrocarpa), white ash (Fraxinus americana), and yellow birch (Betula alleghaniensis) responded less quickly to shade, with absorbance differences appearing later in summer. As for the intolerant butternut (Juglans cinerea), the small differences in absorbance between shaded and sunlit leaves in late July indicated a lower response to shade in its seedling leaves. These results indicated that spectral analysis might be a more appropriate tool to differentiate true sun from shade leaves than the morphological parameters commonly used.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"195 - 202"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A survey of Cycas media in northern Queensland, Australia, showed no differences between males and females in leaf number and stem height. Leaf numbers and stem heights were normally distributed in all populations sampled. The mass of fresh nearly mature seeds from individual females was about three times greater than the mass of the single fresh cone produced by individual males, suggesting that resource allocation to reproduction is greater for females than for males. The proportions of putatively mature individuals participating in the two reproductive episodes evident during the study were between 14% and 38%. On an overall population basis, including immature plants or those otherwise too small to produce cones, the proportion of individuals without reproductive structures ranged from 56% to 93%. Leaf life is of short duration and many naturally defoliated plants were present. Leaf production appears to be stimulated by fire, estimated to occur every 2 or 3 yr. Species belonging to two genera of Coleoptera were collected from male cones shedding pollen, and individuals of the bee Trigona carbonaria were observed collecting pollen from these cones. The genus Trigona is the oldest known fossil bee; it seems possible that it may have collected gymnosperm pollen prior to the origin of angiosperms and that this association has persisted to the present.
{"title":"Size Classes, Reproductive Behavior, and Insect Associates of Cycas media (Cycadaceae) in Australia","authors":"R. Ornduff","doi":"10.1086/337880","DOIUrl":"https://doi.org/10.1086/337880","url":null,"abstract":"A survey of Cycas media in northern Queensland, Australia, showed no differences between males and females in leaf number and stem height. Leaf numbers and stem heights were normally distributed in all populations sampled. The mass of fresh nearly mature seeds from individual females was about three times greater than the mass of the single fresh cone produced by individual males, suggesting that resource allocation to reproduction is greater for females than for males. The proportions of putatively mature individuals participating in the two reproductive episodes evident during the study were between 14% and 38%. On an overall population basis, including immature plants or those otherwise too small to produce cones, the proportion of individuals without reproductive structures ranged from 56% to 93%. Leaf life is of short duration and many naturally defoliated plants were present. Leaf production appears to be stimulated by fire, estimated to occur every 2 or 3 yr. Species belonging to two genera of Coleoptera were collected from male cones shedding pollen, and individuals of the bee Trigona carbonaria were observed collecting pollen from these cones. The genus Trigona is the oldest known fossil bee; it seems possible that it may have collected gymnosperm pollen prior to the origin of angiosperms and that this association has persisted to the present.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"203 - 207"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/337880","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Of the eight stamens in the flower of peanut (Arachis hypogaea L.), four have oblong anthers and four globose ones. Each oblong anther contains four loculi and each globose anther two. The anther wall development follows the basic pattern. Cytomictic channels between microsporocytes were found from pachytene to telophase II. The mature pollen is two-celled. The mature generative cell, which has a PAS positive wall, associates with the vegetative nucleus and may form a male germ unit. There are two ovules, both hemianatropous and bitegmic. Cells of both integuments and nucellus contain starch grains. The nucellar epidermal cells have a larger nucleus, larger starch grains, and thicker walls than other cells of the ovule. A few cells at the micropylar end persist as a nucellar cap. Embryo sac development is of the Polygonum type. The central cell contains many large starch grains, and the antipodal cells are ephemeral. The synergids possess a filiform apparatus. Wall ingrowths occur in the central cell; those at the micropylar end are more massive than those at the chalazal end. Meiosis in microsporocytes occurs earlier and proceeds faster than that in the megasporocyte. The time required for formation, differentiation, and maturation of the generative cell and the egg cell is the same.
{"title":"Development and Structure of Pollen and Embryo Sac in Peanut (Arachis hypogaea L.)","authors":"Xiangyuan Xi","doi":"10.1086/337876","DOIUrl":"https://doi.org/10.1086/337876","url":null,"abstract":"Of the eight stamens in the flower of peanut (Arachis hypogaea L.), four have oblong anthers and four globose ones. Each oblong anther contains four loculi and each globose anther two. The anther wall development follows the basic pattern. Cytomictic channels between microsporocytes were found from pachytene to telophase II. The mature pollen is two-celled. The mature generative cell, which has a PAS positive wall, associates with the vegetative nucleus and may form a male germ unit. There are two ovules, both hemianatropous and bitegmic. Cells of both integuments and nucellus contain starch grains. The nucellar epidermal cells have a larger nucleus, larger starch grains, and thicker walls than other cells of the ovule. A few cells at the micropylar end persist as a nucellar cap. Embryo sac development is of the Polygonum type. The central cell contains many large starch grains, and the antipodal cells are ephemeral. The synergids possess a filiform apparatus. Wall ingrowths occur in the central cell; those at the micropylar end are more massive than those at the chalazal end. Meiosis in microsporocytes occurs earlier and proceeds faster than that in the megasporocyte. The time required for formation, differentiation, and maturation of the generative cell and the egg cell is the same.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"164 - 172"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/337876","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238474","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The soybean (Glycine max [L.] Merr.) is a quantitative short-day (SD) plant requiring two inductive cycles for floral initiation, which occurs first in the most undifferentiated meristem in an axil of a main stem leaf. Floral initiation at the main stem apex, however, requires additional SD inductive cycles. Under continuous SD the transition to flowering in the main stem apex is completed after 8 SD cycles. Differentiation and organogenesis of the first flower in the terminal raceme is apparent after 10 SD cycles. The changes in apical size and geometry, nuclear DNA, and rate of leaf initiation were followed daily during this 10-d period and compared with apices from plants kept under noninductive long days (LD). At emergence all plants had initiated three trifoliolate leaf primordia and during the vegetative stage of development maintained a plastochron of 2.0 d/leaf. The plastochron was shortened to 1.0 d/leaf in SD plants on day 7, just prior to the end of the transition. Apical size and geometry remained unchanged until after 6 SD cycles when height of the dome decreased and there was less elongation of the rib meristem. Earlier events included significantly lower amounts of nuclear DNA in cells of SD apices after 1 and 3 SD cycles. Later, the amount of nuclear DNA increased in cells of SD apices beginning after 5 SD and peaking after 6 SD before decreasing back to control levels. Shifts in increasing proportions of the population of nuclei from the 4C to 2C condition occurred after 1 SD and 3 SD. As in other species, both of these shifts are apparently essential components for the floral transition at the shoot apex in soybean. The first shift, or "mitotic" stimulus, signals that the process of the floral transition has begun, while the second shift, or "floral" stimulus, is required for completion of the process.
{"title":"Shoot Meristem Activity during Floral Transition in Glycine max (L.) Merr.","authors":"Judith F. Thomas, Malee L. Kanchanapoom","doi":"10.1086/337873","DOIUrl":"https://doi.org/10.1086/337873","url":null,"abstract":"The soybean (Glycine max [L.] Merr.) is a quantitative short-day (SD) plant requiring two inductive cycles for floral initiation, which occurs first in the most undifferentiated meristem in an axil of a main stem leaf. Floral initiation at the main stem apex, however, requires additional SD inductive cycles. Under continuous SD the transition to flowering in the main stem apex is completed after 8 SD cycles. Differentiation and organogenesis of the first flower in the terminal raceme is apparent after 10 SD cycles. The changes in apical size and geometry, nuclear DNA, and rate of leaf initiation were followed daily during this 10-d period and compared with apices from plants kept under noninductive long days (LD). At emergence all plants had initiated three trifoliolate leaf primordia and during the vegetative stage of development maintained a plastochron of 2.0 d/leaf. The plastochron was shortened to 1.0 d/leaf in SD plants on day 7, just prior to the end of the transition. Apical size and geometry remained unchanged until after 6 SD cycles when height of the dome decreased and there was less elongation of the rib meristem. Earlier events included significantly lower amounts of nuclear DNA in cells of SD apices after 1 and 3 SD cycles. Later, the amount of nuclear DNA increased in cells of SD apices beginning after 5 SD and peaking after 6 SD before decreasing back to control levels. Shifts in increasing proportions of the population of nuclei from the 4C to 2C condition occurred after 1 SD and 3 SD. As in other species, both of these shifts are apparently essential components for the floral transition at the shoot apex in soybean. The first shift, or \"mitotic\" stimulus, signals that the process of the floral transition has begun, while the second shift, or \"floral\" stimulus, is required for completion of the process.","PeriodicalId":9213,"journal":{"name":"Botanical Gazette","volume":"152 1","pages":"139 - 147"},"PeriodicalIF":0.0,"publicationDate":"1991-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1086/337873","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60238395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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