Responses to water depth and clipping of twenty-three plant species in an Indian monsoonal wetland

Responses of species to disturbances give insights into how species might respond to future wetland changes. In this study, species of monsoonal wetlands belonging to various functional types (graminoid and non-graminoid emergents, submersed aquatic, floating-leaved aquatic) varied in their growth responses to water depth and harvesting. We tested the effects of water depth (moist soil and flooded) and clipping (unclipped and clipped) on the biomass and longevity of twenty-three dominant plant species of monsoonal wetlands in the Keoladeo National Park, India in a controlled experiment. With respect to total biomass and survival, six species responded positively to flooding and twelve species responded negatively to clipping. Responses to flooding and clipping, however, sometimes interacted. Individualistic responses of species to water levels and clipping regimes were apparent; species within a functional group did not always respond similarly. Therefore, detailed information on the individualistic responses of species may be needed to predict the vegetation composition of post-disturbance wetlands. In particular, as demands for fresh water increase around the world, studies of life history constraints and responses to hydrological changes will aid wetland managers in developing strategies to conserve biodiversity

Attitudes, Perceptions, and Personal Problems of Three Groups of High School Students

The problem of the study was to compare three groups of high school seniors--college preparatory, vocational preparatory, and general diploma students--in scholastic achievement, attitudes, and types of personal problems

A multiple-method approach reveals a declining amount of chloroplast DNA during development in Arabidopsis

<p>Abstract</p> <p>Background</p> <p>A decline in chloroplast DNA (cpDNA) during leaf maturity has been reported previously for eight plant species, including <it>Arabidopsis thaliana</it>. Recent studies, however, concluded that the amount of cpDNA during leaf development in Arabidopsis remained constant.</p> <p>Results</p> <p>To evaluate alternative hypotheses for these two contradictory observations, we examined cpDNA in Arabidopsis shoot tissues at different times during development using several methods: staining leaf sections as well as individual isolated chloroplasts with 4',6-diamidino-2-phenylindole (DAPI), real-time quantitative PCR with DNA prepared from total tissue as well as from isolated chloroplasts, fluorescence microscopy of ethidium-stained DNA molecules prepared in gel from isolated plastids, and blot-hybridization of restriction-digested total tissue DNA. We observed a developmental decline of about two- to three-fold in mean DNA per chloroplast and two- to five-fold in the fraction of cellular DNA represented by chloroplast DNA.</p> <p>Conclusion</p> <p>Since the two- to five-fold reduction in cpDNA content could not be attributed to an artifact of chloroplast isolation, we conclude that DNA within Arabidopsis chloroplasts is degraded <it>in vivo </it>as leaves mature.</p