American Journal of Botany
Botanical Society of America
About: American Journal of Botany is an academic journal published by Botanical Society of America. The journal publishes majorly in the area(s): Population & Pollen. It has an ISSN identifier of 0002-9122. Over the lifetime, 15042 publications have been published receiving 612891 citations. The journal is also known as: American journal of botany & Am. j. bot..
Papers published on a yearly basis
TL;DR: A method of fixation in acrolein and embedding in glycol methacrylate polymer is described in detail and in a wide range of plant specimens prepared in this way, stained sections 1-3 microns thick showed excellent preservation of tissue and cell structures.
Abstract: Some easily seen structural features of living plant cells are destroyed or badly distorted by most of the common fixatives and embedding media used in plant histology. In stained sections of plant tissues fixed in FAA (formalin-acetic acid-alcohol mixtures) and embedded in paraffin wax, for example, mitochondria and fine transvacuolar strands of cytoplasm are usually not visible. Many structural features such as these can be preserved, however, with suitable fixatives and embedding media. Fixation in non-coagulant fixatives (e.g., osmium tetroxide, acrolein, glutaraldehyde, formaldehyde) and the use of plastics as embedding media is recommended. A method of fixation in acrolein and embedding in glycol methacrylate polymer is described in detail. In a wide range of plant specimens prepared in this way, stained sections 1-3 microns thick showed excellent preservation of tissue and cell structures. 39 references, 11 figures.
TL;DR: Nine newly explored regions of the chloroplast genome offer levels of variation better than the best regions identified in an earlier study and are therefore likely to be the best choices for molecular studies at low taxonomic levels.
Abstract: Although the chloroplast genome contains many noncoding regions, relatively few have been exploited for interspecific phylogenetic and intraspecific phylogeographic studies. In our recent evaluation of the phylogenetic utility of 21 noncoding chloroplast regions, we found the most widely used noncoding regions are among the least variable, but the more variable regions have rarely been employed. That study led us to conclude that there may be unexplored regions of the chloroplast genome that have even higher relative levels of variability. To explore the potential variability of previously unexplored regions, we compared three pairs of single-copy chloroplast genome sequences in three disparate angiosperm lineages: Atropa vs. Nicotiana (asterids); Lotus vs. Medicago (rosids); and Saccharum vs. Oryza (monocots). These three separate sequence alignments highlighted 13 mutational hotspots that may be more variable than the best regions of our former study. These 13 regions were then selected for a more detailed analysis. Here we show that nine of these newly explored regions (rpl32-trnL((UAG)), trnQ((UUG))-5'rps16, 3'trnV((UAC))-ndhC, ndhF-rpl32, psbD-trnT((GGU)), psbJ-petA, 3'rps16-5'trnK((UUU)), atpI-atpH, and petL-psbE) offer levels of variation better than the best regions identified in our earlier study and are therefore likely to be the best choices for molecular studies at low taxonomic levels.
TL;DR: The results of this study show that a survey using as few as three representative taxa can be predictive of the amount of phylogenetic information offered by a cpDNA region and that rate heterogeneity exists among noncoding cpDNA regions.
Abstract: Chloroplast DNA sequences are a primary source of data for plant molecular systematic studies. A few key papers have provided the molecular systematics community with universal primer pairs for noncoding regions that have dominated the field, namely trnL-trnF and trnK/matK. These two regions have provided adequate information to resolve species relationships in some taxa, but often provide little resolution at low taxonomic levels. To obtain better phylogenetic resolution, sequence data from these regions are often coupled with other sequence data. Choosing an appropriate cpDNA region for phylogenetic investigation is difficult because of the scarcity of information about the tempo of evolutionary rates among different noncoding cpDNA regions. The focus of this investigation was to determine whether there is any predictable rate heterogeneity among 21 noncoding cpDNA regions identified as phylogenetically useful at low levels. To test for rate heterogeneity among the different cpDNA regions, we used three species from each of 10 groups representing eight major phylogenetic lineages of phanerogams. The results of this study clearly show that a survey using as few as three representative taxa can be predictive of the amount of phylogenetic information offered by a cpDNA region and that rate heterogeneity exists among noncoding cpDNA regions.
TL;DR: A refined hypothesis of species phylogeny of section Paeonia was proposed by considering the discordance between the nuclear and cpDNA phylogenies to be results of hybrid speciation followed by inheritance of cpDNA of one parent and fixation of ITS sequences of another parent.
Abstract: The coding region of the mat K gene and two intergenic spacers, psb A-trn H and trn L(UAA)-trn F(GAA), of cpDNA were sequenced to study phylogenetic relationships of 32 Paeonia species. In the psb A-trn H intergenic spacer, short sequences bordered by long inverted repeats have undergone inversions that are often homoplasious mutations. Insertions/deletions found in the two intergenic spacers, mostly resulting from slipped-strand mispairing, provided relatively reliable phylogenetic information. The mat K coding region, evolving more rapidly than the trnL-trn F spacer and more slowly than the psb A-trn H spacer, produced the best resolved phylogenetic tree. The mat K phylogeny was compared with the phylogeny obtained from sequences of internal transcribed spacers (ITS) of nuclear ribosomal DNA. A refined hypothesis of species phylogeny of section Paeonia was proposed by considering the discordance between the nuclear and cpDNA phylogenies to be results of hybrid speciation followed by inheritance of cpDNA of one parent and fixation of ITS sequences of another parent. The Eurasian and western North American disjunct distribution of the genus may have resulted from interrruption of the continuous distribution of ancestral populations of extant peony species across the Bering land bridge during the Miocene. Pleistocene glaciation may have played an important role in triggering extensive reticulate evolution within section Paeonia and shifting distributional ranges of both parental and hybrid species.
TL;DR: The high requirement of calcium and low calcium content of most pollen may conspire to give calcium a governing role in the growth of pollen tubes both in vitro and in situ, and it is suspected that ramifications of this role extend to the self-incompatibilities of plants and to the curious types of arrested tube growth distinguishing, for example, the orchids.
Abstract: BREWBAKER, JAMES L., and BEYOUNG H. KWACK. (U. Hawaii, Honolulu.) The essential role of calcium ion in pollen germination and pollen tube growth. Amer. Jour. Bot. 50(9): 859-865. Illus. 1963.-A pollen population effect occurs whenever pollen grains are grown in vitro. Small pollen populations germinate and grow poorly if at all, under conditions which support excellent growth of large pollen populations. The pollen population effect is overcome completely by a growth factor obtained in water extracts of many plant tissues. This factor is shown to be the calcium ion, and its action confirmed in86 species representing 39plant families. Other ions (K+, Mg++, Na+) serve in supporting roles to the uptake or binding of calcium. The high requirement of calcium (300-5000 ppm, as Ca (NO3)2 4H20, for optimum growth) and low calcium content of most pollen may conspire to give calcium a governing role in the growth of pollen tubes both in vitro and in situ. It is suspected that ramifications ofthis role extend to the self-incompatibilities of plants and to the curious types of arrested tube growth distinguishing, for example, the orchids. A culture medium which proved its merit in a wide variety of pollen growth studies included, in distilled water, 10% sucrose, 100 ppm H3BO3, 300 ppm Ca (NO3)2. 4H20, 200 ppm MgSO4. 7H20