The Effect of Low Stem Temperatures and Stem Incisions on the Translocation of Water

Author Institution: Department of Botany and Plant Pathology, The Ohio State University, Columbus 1

Control of Partitioning and Export of Carbon in Leaves of Higher-Plants

Within source leaves, partition of assimilated carbon and export are regulated to both leaf and plant ontogeny and to environmental conditions. System goals, adaptive responses, control mechanisms, and information flow are developed from the viewpoint that a well-adapted plant is an integrated system. Regulation of partitioning and export involves both feedforward control and feedback homeostasis. Export is controlled by regulation of metabolism which supplies assimilated material to be translocated, by control of efflux into the free space of material destined for export, and by regulation of phloem loading. Control of export by the latter two processes depends on responsive metabolic processes that can supply sucrose and other transport molecules upon demand. An integrated model incorporating these features posits that control of export by mechanisms located in the source leaves is an important means of regulating translocation

General lighting requirements for photosynthesis

This paper presents data that suggests some criteria for evaluating growth chamber and greenhouse lighting. A review of the general lighting requirements for photosynthesis reveals that four aspects of light are important: irradiance, quality, timing, and duration. Effective lighting should produce plants that perform according to the goals of the project. For example, for physiological studies the plants probably should exhibit morphology and physiology similar to that found in field-grown plants. For other projects the criteria will obviously be set according to the reason for raising the plants

An Observation on the Protoplasmic Connections Through Sieve Plates

Author Institution: Department of Botany and Plant Pathology, The Ohio State University, Columbus 10wo electron micrographs of paradermal sections of veins of the leaves of Beta vulgaris are presented. The micrographs show the endoplasmic reticulum from one sieve cell passing through the sieve plate and into the adjacent sieve cell. This is evidently an unusual condition in this materia

Establishment of a Prairie on a Borrow-Pit Site at the Bergamo-Mt. St. John Nature Preserve in Greene County, Ohio

Author Institution: Department of Biological Sciences, University of Cincinnati and Department of Biology, University of DaytonDuring the spring of 1986, development of a prairie was begun on a site at the Bergamo-Mt. St. John Nature Preserve located in Greene County, Ohio. A major objective of the project was to reclaim a sand and gravel borrow-pit. Prairie was chosen for reclamation of this area because prairie vegetation was present in the immediate area and that type of community is well-suited to the extremes in moisture conditions on the site. The prairie is intended to provide a habitat for some species being displaced by human disturbance and to provide a specific plant community within the preserve. To establish grasses, seeds obtained from Western sources were planted in April of 1986 by hydroseeding on the graded site. Just prior to this, seeds of several forbs obtained from Western sources were broadcast over the area. Subsequently, seeds of grasses and forbs collected locally were broadcast. For species more difficult to establish, plants were propagated in soil-filled plastic-film cylinders. These, and other plants collected locally from disturbed sites, were transplanted into holes prepared with a soil auger. After three seasons of growth, approximately 36 species of Ohio prairie indicator plant species, along with a number of species of animals, have become established on the site despite the severe drought of 1988

Flowering Phenology Change and Climate Warming in Southwestern Ohio

Global surface temperature has increased markedly over the last 100 years. This increase has a variety of implications for human societies, and for ecological systems. One of the most obvious ways ecosystems are affected by global climate change is through alteration of organisms’ developmental timing (phenology). We used annual botanical surveys that documented the first flowering for an array of species from 1976 to 2003 to examine the potential implications of climate change for plant development. The overall trend for these species was a progressively earlier flowering time. The two earliest flowering taxa (Galanthus and Crocus) also exhibited the strongest shift in first flowering. We detected a significant trend in climate suggesting higher temperatures in winter and spring over the sampling interval and found a significant relationship between warming temperatures and first flowering time for some species. Although 60% of the species in our study flowered earlier over the sampling interval, the remaining species exhibited no statistically detectable change. This variation in response is ostensibly associated with among-species variation in the role of climate cues in plant development. Future work is needed to isolate specific climate cues, and to link plant phenology to the physiological processes that trigger plant development

The Marine Nature of Nuwuk Lake and Small Ponds of the Peninsula of Point Barrow Alaska

Discusses a score or more ponds, some transient, some persistent, on this narrow gravel spit, their location, nature, salinity and temperature; their biotas, marine and fresh-water, are outlined. Nuwuk Lake, the largest water body of the locality, approx. 600 ft long, max. depth 18.5 ft, is treated in some detail: its bottom, its formation by converging currents of the Bering and Chukchi Seas, ice conditions, temperature, salinity and O2-content. The biotas: euryhaline, reduced shallow-sea fauna are dealt with and the organisms collected during 1952-1960 are tabulated. Comparison is made with the few halocline lakes known in northern Russia and Scandinavia, notably Mogil'noye on Kil'din Island

Mapping the drivers of parasitic weed abundance at a national scale : a new approach applied to Striga asiatica in the mid‐west of Madagascar

The parasitic weed genus Striga causes huge losses to crop production in sub‐Saharan Africa, estimated to be in excess of $7 billion per year. There is a paucity of reliable distribution data for Striga ; however, such data are urgently needed to understand current drivers, better target control efforts, as well as to predict future risks. To address this, we developed a methodology to enable rapid, large‐scale monitoring of Striga populations. We used this approach to uncover the factors that currently drive the abundance and distribution of Striga asiatica in Madagascar. Two long‐distance transects were established across the middle‐west region of Madagascar in which S. asiatica abundance in fields adjacent to the road was estimated. Management, crop structure and soil data were also collected. Analysis of the data suggests that crop variety, companion crop and previous crop were correlated with Striga density. A positive relationship between within‐field Striga density and the density of the nearest neighbouring fields indicates that spatial configuration and connectivity of suitable habitats is also important in determining Striga spread. Our results demonstrate that we are able to capture distribution and management data for Striga density at a landscape scale and use this to understand the ecological and agronomic drivers of abundance. The importance of crop varieties and cropping patterns is significant, as these are key socio‐economic elements of Malagasy cropping practices. Therefore, they have the potential to be promoted as readily available control options, rather than novel technologies requiring introduction