The parameters of grain filling and yield components in common wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. durum)
Final grain dry weight, a component of yield in wheat, is dependent on the duration and the rate of grain filling. The purpose of the study was to compare the grain filling patterns between common wheat, (Triticum aestivum L.), and durum wheat, (Triticum turgidum L. var. durum), and investigate relationships among grain filling parameters, yield components and the yield itself. The most important variables in differentiating among grain filling curves were final grain dry weight (W) for common wheat genotypes and grain filling rate (R) for durum wheat genotypes; however, in all cases the sets of variables important in differentiating among grain filling curves were extended to either two or all three parameters. Furthermore, in one out of three environmental conditions and for both groups of genotypes, the most important parameter in the set was grain filling duration (T). It indicates significant impact of environmental conditions on dry matter accumulation and the mutual effect of grain filling duration and its rate on the final grain dry weight. The medium early anthesis date could be associated with further grain weight and yield improvements in wheat. Grain filling of earlier genotypes occurs in more temperate environments, which provides enough time for gradual grain fill and avoids the extremes of temperature and the stress of dry conditions.
Relationship Between Grain Growth and Postanthesis Leaf Area Duration in Dwarf, Semidwarf and Tall Isogenic Lines of Wheat
Experiments were carried out during 1992 and 1993 growing seasons using in the former year 2 (an early and late) sowing dates. Plants of three isogenic lines (standard height, semidwarf and dwarf) of wheat were grown under field conditions with no restrictions on water or nutrient availability with the objective of determining whether differences in rate of grain growth and in final grain weight were related To differences in leaf area duration postanthesis (LAD). A logistic and an optimization model were used to estimate the components of final grain weight and their performances were compared. The optimization model appeared more appropriate than the logistic to estimate final grain weight and their components (i.e. rate of grain growth and duration of grain filling). 
 
 
 
The dwarf line presented the lowest average grain weight followed by the semidwarf and standard height lines, respectively. However, changes in grain weight due to the action of Rht alleles were independent of the I, AD, suggesting that reductions in grain weight due to delayed sowing date could be associated with a direct effect of temperature on grain development. 
 
 
 
Changes in final grain weight were associated with changes in rate of grain growth, but nor with duration of the grain filling period, demonstrating that rate of grain growth was the main factor responsible for final grain weight.
Investigations on the rôle of organic matter in plant nutrition
1. As the result of decomposition of green manure in a swamp soil, the coarse fractions (including coarse and fine sand) of the surface layer (first 3 inches) decreased by 11·2 per cent. while the fine ones (silt+clay) increased by 9·8 per cent. in the course of 43 days. The effect was less pronounced in the manured soil maintained at 60 per cent. saturation, while no alteration was to be noticed in the case of the unmanured specimens. 2. Treatment with dilute hydrochloric acid prior to dispersion had no appreciable effect on the estimates of mechanical composition obtained in the different cases. Loss in solution was also comparatively small. 3. The silica-sesquioxide ratio increased slightly as the result of decomposition of green manure in swamp soil. The composition of the fine fractions was also altered, the total percentages of the oxides of iron, aluminium and silicon increasing from 90·5 to 99·3 in the course of 71 days. 4. The practical significance of the above and related observations has been discussed.