No abstract

Study was done to compare the response of Triticum aestivum (hexaploid), Triticum durum (tetraploid) and Triticum monococcum (diploid) wheat species to the elevated CO2 using Free Air CO2 Enrichment (FACE) facility. It was demonstrated that the modern cultivar of wheat Triticum aestivum (hexaploid) was largely sink limited. It appeared to have less photosynthesis per unit leaf area than Triticum monococcum (diploid wheat). While leaf size, grain weight and amylase activity increased with the ploidy level from diploid to hexaploid wheat forms, the photosynthetic rate was reduced significantly. These wheat species responded differentially to the elevated CO2. The larger leaf area and greater seed weight and presence of 38 KDa protein band caused by elevated CO2 had additive effect in improving the productivity of hexaploid wheat by changing the source sink ratio. Whereas, such a source sink balance was not induced by elevated CO2 in diploid wheat. The increasing CO2 may present opportunities to breeders and possibly allow them to select for cultivars responsive to the elevated CO2 with better sink potential.

Abstract. The electron and ion temperature at the lowlatitude ionosphere exhibits a wide variety of fluctuations. Observations using SROSS-C2 satellite RPA payload during 1995-2000 provide an excellent opportunity to study the fluctuations in T e and T i in the upper ionosphere and to understand the dynamic processes existing at those altitudes. The spectral analysis of electron and ion temperatures using Fourier and wavelet techniques reveal the presence of quasiperiodicities, such as 14-day, 19-day, 27-day, 55-day, 154-day, 180-day, 1-year and 1.3-year periods. The daytime and nighttime values of T e and T i exhibit different types of characteristic variations. The wavelet spectrum presented depicts the temporal evolution the power of each periodicity present in the daytime and nighttime values of T e and T i . The time evolution of electron and ion temperatures are compared with that of A p and 10.7 cm solar radio flux, to infer the source of temperature fluctuations at the upper ionosphere.

No abstract

[1] The ion and electron F region plasma measurements made by the ion and electron Retarding Potential Analyzers (RPAs) onboard the Indian satellite SROSS-C2, have yielded excellent data set over the Indian region for more than half a solar cycle, after the SROSS-C2 launch in May 1994. The absolute ion density, ion temperature, and ion composition parameters are derived from these in situ measurements and used by many workers. In this paper the absolute values of ion density derived from the ion RPA measurements are compared and evaluated with the measurements made by ground-based ionosondes located in the Indian region and close to the SROSS-C2 orbital path. It is shown that a slight adjustment in efficiency factor of the ion RPA sensor brings the in situ measurements much closer to those obtained from the ground-based ionosonde measurements taking into account the model calculations. It may be mentioned that this is a correction to the ion density measurement by SROSS-C2 by a fixed proportion (14-11.4%). The effect of change in efficiency factor on the ion current, which is used to deduce the ion number density, is demonstrated and discussed.