No abstract

This paper reports a 4-month study that investigated the effectiveness of curriculum materials incorporating the history of science (HOS) on learning science, understanding the nature of science (NOS), and students' interest in science. With regards to these objectives, three different class contexts were developed with three main types of information in history of science. In the first class context, the similarities between students' alternative ideas and scientific concepts from the HOS were considered in developing teaching materials. In the second class context, the teacher developed discussion sessions on the ways scientists produce scientific knowledge. In the third class context, short stories about scientists' personal lives were used without connection to the concepts of science or NOS. Ninety-one eighth-grade students were randomly assigned to four classes taught by the same science teacher. The concepts in the motion unit and in the force unit were taught. Three of the four classrooms were taught using the contexts provided by the HOS while the fourth class was taught in the same way that the teacher had used in previous years. The effects on student meaningful learning, perceptions of the NOS, and interest in science were evaluated at the beginning, at the middle, and at the end of the study to compare differences between historical class contexts and the Traditional Class. Results of analysis showed that the changes in meaningful learning scores for the first class context were higher than other classes but the differences between classes were not significant. The HOS affected student perceptions of the scientific methods and the role of inference in the process of science. Stories from scientists' personal lives consistently stimulated student interest in science, while discussions of scientific methods without these stories decreased student interest. The positive effects of stories relating scientist' personal life on student interest in science has major importance for the teaching of science. This research also helps to clarify different class contexts which can be provided with different types and uses of historical information.

The plasticity of white clover (Trifolium repens L.) results in changes in plant habit in response to different environmental stresses. The objective of this research was to characterize those morphological changes associated with plasticity in white clover clones derived from ‘Osceola’, ‘Grassland Huia’, and SRVR germplasm. Clones were exposed to treatments in the following two‐way factorial design: no clipping or clipping on 7‐d intervals and barrier to stolon rooting or no barrier. In a three‐season greenhouse test, 90 clones were measured for leaf dry weight (DW), stolon DW, stolon length, root DW, and apex number. Generated parameters were herbage DW (leaf DW + stolon DW), biomass DW (root DW + herbage DW), leaf‐to‐stem ratio (leaf DW ÷ stolon DW), and herbage‐to‐root ratio (herbage DW ÷ root DW). Plant means were significantly reduced for all traits and ratios with repeated clipping. The rooting barrier significantly reduced apex number, root DW, and the leaf‐to‐stem ratio while increasing the stolon DW and the herbage‐to‐root ratio. The interaction of root barrier and repeated clipping was significant for apex number, root DW, and the herbage‐to‐root ratio. Near zero correlations for the same measurements made on the same clone grown with different stress treatments suggest genetic differences in the magnitude of plasticity. Path analysis further described changes in relationships among traits for plants exposed to different stresses. The magnitude of plasticity appeared to be a clone‐specific phenomenon that may frustrate verifying gain with selection for progenies of selections evaluated in different environments.

Orchardgrass (Dactylis glomerata L.) genotypes from different natural sources in the Eastern Anatolian Region of Turkey were clonally evaluated to study genetic variation and the relationships between seed yield and its components using a randomized complete block design. Results showed very significant genotypic variances among genotypes for all traits, including agronomic (seed, dry matter, and biological yields), morphological (plant height; panicle length; crown diameter; numbers of fertile, sterile, and total stems; and stem intensity), physiological (percent fertile stems, harvest and fertility indexes), and phenological (heading and anthesis dates) traits, as well as genotype × year interaction variances. Genotypic components were the main contributor to phenotypic variation of all traits (except physiologic traits, stem intensity, and number of sterile stems), resulting in high broad-sense heritability (>50%). Agromorphological and physiological traits had greater phenotypic (PCV), genotypic (GCV), and environmental coefficients of variation, while these were lower for phenological traits. After the phenological traits, plant height, crown diameter, and panicle length were the least variable traits, while stem intensity and fertility index were highly variable. Heritability estimates increased as GCV values approached PCV values. Expected genetic gain greatly increased as heritability estimates and PCV both increased, rather than heritability values alone. The first 5 principle components accounted for 84.90% of total variance. All agromorphological traits (except number of sterile stems) and fertile stem percentage were primary sources of variation of the PC1 axis, while harvest and fertility indexes were for PC2. Out of the 4 clusters, genotypes in cluster 4 of higher seed yield were faster in aboveground biomass accumulation. They also had the best agromorphological traits coupled with early maturity. Seed yield greatly increased as aerial biomass increased without any change in harvest index, but there was a significant decrease in fertility index. It was concluded that selection for dry matter yield could result in a simultaneous increase in seed yield.

An irrigated field study was conducted to determine the relative importance and inter-relationships of growth parameters of three dormant alfalfa (Medicago sativa L.) cultivars grown in the highlands of Eastern Anatolia, Turkey, in 2000-2003. The fast-growing cultivar Savas had the greatest dry matter (DM) yield at the final sampling date with the greatest mean crop growth rate. In addition to a greater relative growth rate (RGR), this cultivar had more stem branching and greater leaf area in the canopy, which resulted in greater leaf area index (LAI) and greater leaf area duration. Despite the considerable increase in leaf area ratio (LAR: leaf area per unit shoot DM), the reduction in RGR of all cultivars over time was the result of a large decline in net assimilation rate (NAR) due to increasing specific leaf area (SLA). Intracultivar variation in the RGR of alfalfa is mainly determined by NAR and SLA, and both were significantly higher for Savas than the other two cultivars. The relative importance of NAR and SLA to RGR changed due to increasing self-shading as the LAI of the canopy increased, creating a trade-off between NAR and SLA.