Patterns of Stem Cell Divisions Contribute to Plant Longevity

The lifespan of plants ranges from a few weeks in annuals to thousands of years in trees. It is hard to explain such extreme longevity considering that DNA replication errors inevitably cause mutations. Without purging through meiotic recombination, the accumulation of somatic mutations will eventually result in mutational meltdown, a phenomenon known as Muller’s ratchet. Nevertheless, the lifespan of trees is limited more often by incidental disease or structural damage than by genetic aging. The key determinants of tree architecture are the axillary meristems, which form in the axils of leaves and grow out to form branches. The number of branches is low in annual plants, but in perennial plants iterative branching can result in thousands of terminal branches. Here, we use stem cell ablation and quantitative cell-lineage analysis to show that axillary meristems are set aside early, analogous to the metazoan germline. While neighboring cells divide vigorously, axillary meristem precursors maintain a quiescent state, with only 7–9 cell divisions occurring between the apical and axillary meristem. During iterative branching, the number of branches increases exponentially, while the number of cell divisions increases linearly. Moreover, computational modeling shows that stem cell arrangement and positioning of axillary meristems distribute somatic mutations around the main shoot, preventing their fixation and maximizing genetic heterogeneity. These features slow down Muller’s ratchet and thereby extend lifespan.

87Sr/86Sr ratios of middle Miocene to Pleistocene planktonic foraminifers from ODP Site 117-722 (Table 3)

Continuous magnetostratigraphy and biostratigraphy made it possible to construct a detailed late Neogene record of 87Sr/86Sr isotopic ratios of ocean water, as measured in the tests of planktonic foraminifers. Sediments recovered during Leg 117, in the western Arabian Sea, provide a continuous, high resolution sedimentary record from the early Miocene to present. The late Miocene to Recent is marked by rapidly increasing 87Sr/86Sr ratios in seawater, which results in a chronostratigraphical resolution varying from 0.2 Ma to 1.5 Ma. The 87Sr/86Sr seawater curve has a stepwise character similar to the one determined by DePaolo on Site 590B, in the Tasman Sea, and to the one determined by McKenzie on Site 653A, in the Mediterranean, confirming its use as a chronostratigraphic tool for this time span. Periods of rapid increase in the 87Sr/86Sr isotopic ratio of seawater are correlated with important changes in tectonic and climatic conditions. Experiments showed that bulk carbonate sediment samples have differing 87Sr/86Sr ratios from those of planktonic and benthic foraminifers from the same depth.

Theologiae R.P. Fr. Suarez e Societate Jesu, summa, seu compendium /

Table of contents at end of each volume.

D. Martin Luthers Werke.

This book is a pre-publication prospectus of the Weimar Edition of Luther's Works. It contains a table of contents as well as the anticipated publication date for each forthcoming volume. As they are printed, each volume of Luther's works will be divided into four "series": I: Werke; II: Tischreden; III: Deutsche Bibel; IV: Briefe.

The roll of the Royal College of Physicians of London : comprising biographical sketches of all the eminent physicians whose names are recorded in the Annals from the foundation of the college in 1518 to its removal in 1825, from Warwick Lane to Pall Mall East /

Includes indexes.

An ecclesiastical history, ancient and modern : from the birth of Christ to the beginning of the eighteenth century /

Chronological tables and indexes in v. 6.

The Turnament of Totenham and the Feest. Two early ballads printed from a manuscript preserved in the public library of the University of Cambridge.

Edited by Thomas Wright. Ascribed in early editions to Gilbert Pilkington, who was probably only the transcriber of part of the manuscript. cf. Camb. univ. Cat. of mss., v. 2, p. 505, and Dict. nat. biog.

The history of Fairfield, Fairfield County, Connecticut, from the settlement of the town in 1639 to 1818,

No more published.

An index to the wills and inventories now preserved in the Probate registry, at Chester ...

Report of the Record Society for the year 1896/97 contained in v. 1, 1897/98 in v. 2.

A history of the French novel (to the close of the 19th century) /

Includes "bibliographical notes" (vol. 1, p. 479-482) and index.

Admissions to Trinity College, Cambridge ...

"Members of Kings's hall" by A.E. Stamp: v. 1, p. [79]-140.

Histoire naturelle de l'ame /

Includes "Lettre critique de Mr. de la Mettrie sur L'histoire naturelle de l'ame. A madame la marquise du Chatelet," 12 pages at the end.

Elgar,

Series title also at head of t.p.

“If you don’t want to leave him out, go ahead”: Constructing belonging of non-native animals during Native American parent-child dyad play with a diorama

Thesis (Master's)--University of Washington, 2016-06

Predictors and outcomes of early motherhood in the Australian Longitudinal Study on Women's Health

Early motherhood is identified as a social problem, and having children at an early age is assumed to lead to psychological distress, welfare dependence and socioeconomic disadvantage. Analysis of responses from 9,689 young participants in the Australian Longitudinal Study on Women's Health was used to examine predictors and outcomes of early motherhood in Australia. Survey 1 (1996, aged 18 - 23) and Survey 2 (2000, aged 22 - 27), were used to categorize women as Childless, Existing Mothers (before Survey 1) and New Mothers (became mothers before Survey 2). Multivariate logistic regressions provided comparisons on sociodemographics, gynaecological variables, psychological wellbeing and health behaviours. Survey 1 data show that Existing Mothers experience socioeconomic disadvantages and unhealthy lifestyles. However, those who will go on to become mothers earlier than their peers already experience similar disadvantages. Further, the Survey 2 data show that, when these pre-existing disadvantages are controlled for, the additional deficits experienced by early mothers are relatively minor. Social disadvantage predisposes women to become mothers early, and to adopt unhealthy behaviours. However, young Australian women cope well with the challenges of early motherhood. In the longer term, unhealthy lifestyles and low education may lead to ill health and disadvantage, but early motherhood is not the initiator of this trajectory.