Iowa State University

About: Iowa State University is a education organization based out in Ames, Iowa, United States. It is known for research contribution in the topics: Population & Gene. The organization has 50151 authors who have published 107716 publications receiving 3355909 citations. The organization is also known as: Iowa State University of Science and Technology & Iowa State College.

The Combined Effect of Drought Stress and Heat Shock on Gene Expression in Tobacco

Abstract: In nature, plants encounter a combination of environmental conditions that may include stresses such as drought or heat shock. Although drought and heat shock have been extensively studied, little is known about how their combination affect plants. We used cDNA arrays, coupled with physiological measurements, to study the effect of drought and heat shock on tobacco (Nicotiana tabacum) plants. A combination of drought and heat shock resulted in the closure of stomata, suppression of photosynthesis, enhancement of respiration, and increased leaf temperature. Some transcripts induced during drought, e.g. those encoding dehydrin, catalase, and glycolate oxidase, and some transcripts induced during heat shock, e.g. thioredoxin peroxidase, and ascorbate peroxidase, were suppressed during a combination of drought and heat shock. In contrast, the expression of other transcripts, including alternative oxidase, glutathione peroxidase, phenylalanine ammonia lyase, pathogenesis-related proteins, a WRKY transcription factor, and an ethylene response transcriptional co-activator, was specifically induced during a combination of drought and heat shock. Photosynthetic genes were suppressed, whereas transcripts encoding some glycolysis and pentose phosphate pathway enzymes were induced, suggesting the utilization of sugars through these pathways during stress. Our results demonstrate that the response of plants to a combination of drought and heat shock, similar to the conditions in many natural environments, is different from the response of plants to each of these stresses applied individually, as typically tested in the laboratory. This response was also different from the response of plants to other stresses such as cold, salt, or pathogen attack. Therefore, improving stress tolerance of plants and crops may require a reevaluation, taking into account the effect of multiple stresses on plant metabolism and defense.

Fitting variogram models by weighted least squares

Abstract: The method of weighted least squares is shown to be an appropriate way of fitting variogram models. The weighting scheme automatically gives most weight to early lags and down-weights those lags with a small number of pairs. Although weights are derived assuming the data are Gaussian (normal), they are shown to be still appropriate in the setting where data are a (smooth) transform of the Gaussian case. The method of (iterated) generalized least squares, which takes into account correlation between variogram estimators at different lags, offer more statistical efficiency at the price of more complexity. Weighted least squares for the robust estimator, based on square root differences, is less of a compromise.

The Choice of Organizational Form: The Case of Franchising

Abstract: Evaluates the agency problems associated with company owned versus franchised units in order to determine whether these agency considerations affect the own/franchise decision. Information on the ownership characteristics of franchise firms were gathered from 112 responses to queries sent to franchise companies listed in the 1982 Norback and Norback and the 1983 Siegel franchise directories. Monitoring problems and costs and franchising contract provisions are discussed. Results support the prediction that the owned units, which presumably entail more on-site monitoring, are located closer to central or regional headquarters than franchised units. In addition, the likelihood of franchising increases with higher monitoring costs, low initial investment costs per unit, and higher frequency of repeat customers. (SFL)

The relational-interdependent self-construal and relationships.

Abstract: Three studies describe the development and validation of a measure of the relational-interdependent self-construal, which is defined as the tendency to think of oneself in terms of relationships with close others. Study 1 reports the development, psychometric properties, and tests of validity of this new measure. Individuals who scored high on the Relational-Interdependent Self-Construal (RISC) Scale characterized their important relationships as closer and more committed than did individuals who scored low on this measure (Study 1) and were more likely to take into account the needs and wishes of others when making decisions (Study 2). In Study 3, using a dyadic interaction paradigm with previously unacquainted participants, the partners of persons who scored high on the RISC scale viewed them as open and responsive to their needs and concerns; these perceptions were related to positive evaluations of the relationship.