Performance of Sesbania–Sunflower under Different Cropping Systems using 15N and 13C

A field experiment on sesbania (ses) and sunflower (sun) plants grown in monocropping and intercropping systems (1ses:1sun; 1ses:2sun, and 2ses:1sun, row ratio) was conducted to evaluate growth and N2-fixation using 13C and 15N natural abundance techniques. The results showed that 1ses:1sun surpassed the other treatments in terms of nitrogen (N) and dry matter yields (DM). However, 1ses:2sun gave the highest seed and oil production and showed the greatest N2-fixation. Sesbania plants in the 1ses:2sun fixed almost identical amounts of N2 in mono and intercropping systems. Moreover, soil N-uptake was the lowest among other treatments. These results give an advantage to the 1ses:2sun treatment over other treatments in terms of soil N consumption and N2 fixation to meet sesbania's N requirements. Nevertheless, 2ses:1sun seemed to be an inappropriate treatment. On the other hand, it could be suggested from ‰D13C data that plants in the intercropping systems appeared not to be subjected to any abiotic stress during the growing period

Growth, Nitrogen Uptake and Carbon Isotope Discrimination in Barley Genotypes Grown under Saline Conditions

The effect of different salinity levels of irrigation water (ECw range 1-12 dS/m) on dry matter yield, nitrogen uptake, fertilizer nitrogen use efficiency (%NUE), stomatal conductance and carbon isotope discrimination (Δ13C‰) in three barley genotypes originating from different geographic areas (Arabi.Abiad, Syria; Pk-30-136, Pakistan and WI-2291, Australia) was investigated in a pot experiment. An increase in salinity resulted in a decrease in Δ13C in all the genotypes. Increasing salinity reduced leaf stomatal conductance which was less pronounced in WI-2291 comparing to other genotypes. At high salinity level, the reduction in Δ13C corresponded to a considerable decrease in the ratio (Ci/Ca) of intercellular (Ci) and atmospheric (Ca) partial pressures of CO2 in all the genotypes indicating that such a decrease was mainly due to the stomatal closure. Moreover, since the reduction in dry matter yield in all the genotypes grown at 12 dS/m did not exceed 50% in comparison with their controls, the photosynthetic apparatus of all studied genotypes seemed to be quit tolerant to salinity. At the moderate salinity level (8 dS/m), the enhancement of leaf dry matter yield in the WI2291 genotype might have been due to positive nutritional effects of the salt as indicated by a significant increase in nitrogen uptake and NUE. Thus, the lower Ci/Ca ratio could result mainly from higher rates of photosynthetic capacity rather than stomatal closure. On the other hand, relationships between dry matter yield or NUE and Δ13C seemed to be depending on plant genotype, plant organ and salinity level. Based on growth, nutritional and Δ13C data, selection of barley genotypes for saline environments was affected by salinity level. Therefore, such a selection must be achieved for each salinity level under which the plants have been grown

Interactions entre le milieu et les deux partenaires de la symbiose Alnus/Franki mises en evidence par l'estimation de l'activite fixatrice de l'azote a l'aide des methodes "1"5N

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Growth and Nitrogen Fixation in Silicon and/or Potassium Fed Chickpeas Grown under Drought and Well Watered Conditions

A pot experiment was conducted to study the effects of silicon (Si) and/or potassium (K) on plant growth, nitrogen uptake and N2-fixation in water stressed (FC1) and well watered (FC2) chickpea plants using 15N and 13C isotopes. Three fertilizer rates of Si (Si50, Si100 and Si200) and one fertilizer rate of K were used. For most of the growth parameters, it was found that Si either alone or in combination with K was more effective to alleviate water stress than K alone. Increasing soil water level from FC1 to FC2 often had a positive impact on values of almost all studied parameters. The Si100K+ (FC1) and Si50K+ (FC2) treatments gave high enough amounts of N2-fixation, higher dry matter production and greater nitrogen yield. The percent increments of total N2-fixed in the above mentioned treatments were 51 and 47% over their controls, respectively. On the other hand, increasing leave’s dry matter in response to the solely added Si (Si50K- and Si100K-) is associated with lower Δ13C under both watering regimes. This may indicate that Si fertilization had a beneficial effect on water use efficiency (WUE). Hence, Δ13C could be an adequate indicator of WUE in response to the exogenous supply of silicon to chickpea plants. Our results highlight that Si is not only involved in amelioration of growth and in maintaining of water status but it can be also considered an important element for the symbiotic performance of chickpea plants. It can be concluded that the synergistic effect of silicon and potassium fertilization with adequate irrigation improves growth and nitrogen fixation in chickpea plants

Evaluation of Water Stress Tolerance in Advanced Breeding Lines of Durum and Bread Wheat Using 13C

Dry matter (DM), nitrogen uptake (TN) along with water (WUE) and nitrogen (15NUE) use efficiencies in twelve advanced breeding lines (ACSAD) and two varieties (Cham1&6) of durum (DW) and bread (BW) wheat grown under well water (I1) and water stress conditions (I2) were evaluated using 15N and Δ13C. Water stress decreased Δ13C in all studied genotypes. The extent of the decrease in Δ by stress was relatively higher in BW (-1.08‰) than DW (-0.8‰). Cham1 (DW) exhibited the highest DM, TN, NUE, WUE and Δ13C values under I1, indicating its suitability to be grown under irrigated conditions. However, ACSAD1261 (DW) seemed to be a promising line to be grown in semi arid areas due to higher values in the aforementioned criteria under I2. For BW, the highest DM of ACSAD59 under I1 may suggest its suitability to be grown under well irrigated conditions. However, DM of ACSAD883 and 1115 were not affected by watering regime. Additionally, due to the high DM of Cham6 and ACSAD1135 in both watering regimes, and because of the decrease in Δ13C values under stress, it can be suggested that they could be suitable for both irrigated and water stress conditions. Since Δ13C values were affected by wheat genotype and watering regime as a result of the effects on the balance between stomatal conductance and carboxilation, it cannot be relied, completely, upon this technique to select drought tolerant genotypes. Therefore, we suggest that using Δ13C along with agro-physiological parameters are better selection criteria for water stress tolerance in breeding programs than when used separately