Distribution of 14CO2 during ontogeny of chickpea (Cicer arietinum) grown at two moisture levels

The distribution of assimilates of ¹⁴CO₂ in ethanol soluble and insoluble fractions was measured at 20-day intervals from 45–135 days after sowing (DAS) in chickpea (Cicer arietinum) grown at two moisture levels. The contribution of pre-flowering assimilates to pods, although very low, was higher under the stress conditions. At the time of harvest, the recovery of ¹⁴C in pods was 0.4 and 0.9% of the total ¹⁴C fed 45 DAS in soluble and 2.5 and 5.1% in insoluble fractions in control and stressed plants, respectively. The %¹⁴C received by nodules continuously decreased with increasing age of plants. Stressed plants diverted more ¹⁴C to nodules, compared to control, during vegetative and flowering stages. During active seed filling, stressed plants diverted more ¹⁴C to reproductive parts and less to nodules, compared to control. Significant amounts of ¹⁴C were retgined by the stem and leaves during the seed-filling period and it appears that there is scope for the remobilisation of pre-flowering, as well as post-flowering assimilates for seed-filling of chickpea.     

Partitioning and Utilization of Carbon and Nitrogen in Nodulated Roots and Nodules of Chickpea (Cicer arietinum) Grown at Two Moisture Levels

The partitioning and utilization of carbon (C) and nitrogen(N) in nodulated roots and nodules of chickpea (Cicer arietinumL.) was studied at two moisture levels at 10-d intervals 40–140d after sowing (DAS). More C was used in respiration and lessin growth of nodulated roots and nodules under water stresscompared to controls during all growth stages except at theearly vegetative stage. Similarly, less nitrogen was investedin dry matter of both nodules and nodulated roots under stress,except during the vegetative stage where more nitrogen was used.Calculated over the entire growth period, as much as 14 and20% of the total nitrogen and 3 and 4% of the total carbon fixedby the plant was lost to the rooting medium under controlledand stressed conditions, respectively. The efficiency of nitrogen fixation with respect to net C utilizationwas maximal during seed filling under both control and stressconditions However, the efficiency of nitrogen fixation wasalways greater under drier conditions. Carbon, chickpea (Cicer arietinum L.), nitrogen, nitrogen fixation, partitioning     

Fungicidal control of Macrophomina phaseolina altered in pathogenicity by substrate nutrients

The presence of different carbon and nitrogen sources and bivalent metal compounds in the substrate medium influenced the mycelial growth of Macrophomina phaseolina and in vitro susceptibility to fungicides. The inoculum from such substrate media showed differences in pathogenicity on mung bean (Vigna radiata). Sucrose and asparagine significantly increased the mycelial growth as well as pathogenicity of the fungus. Absence of bivalent metal ions, viz., Fe⁺⁺, Zn⁺⁺ and Mg⁺⁺ in the medium produced inoculum which caused maximum seedling mortality and foliage blight. Carbendazim and thiophanate-M as seed treatments were significantly less effective when the inoculum was from a medium containing glucose than when the inoculum was from a medium containing sucrose. Captafol and thiram gave significantly better disease control on mung bean when the inoculum used for soil inoculations was from media containing asparagine and ammonium nitrate compared to the inoculum grown on a medium containing sodium nitrate. Carbendazim, thiophanate-M, PMA, captafol and thiram gave good disease control when the inoculum used was raised on a medium devoid of bivalent metal ions. Carbendazim and thiophanate-M were the best fungicides as foliar treatments and controlled the disease irrespective of carbon, nitrogen and bivalent metal ion status of the substrate medium used for the production of inoculum.     

A Practical Examination of the Use of Geostatistics in the Remediation of a Site with a Complex Metal Contamination History

Targeted remediation strategies offer the potential to treat only those areas where contamination exceeds predefined threshold levels. We used geostatistical techniques to characterize spatial distribution of heavy metals across a contaminated site, with the aim of delineating the contaminants, which is essential for successful implementation of targeted remediation strategies. Samples collected from three depths, 0–20 cm, 20–40 cm and 40–60 cm at 50 sample locations, were analyzed for As, Sb, Hg, Pb, Cd and Cu contents. The geostatistical analysis of this data enabled the identification of a number of contamination hotspots and trends. The visual interpretation of the data was supported by the statistical analysis in the form of Spearman's rank correlation coefficient. Additionally, classical statistics, based on the central limit theorem, showed that, in terms of obtaining the true mean for each of the contaminants within acceptable limits of precision, the site has been more than adequately sampled.It has been demonstrated that kriging can offer the potential to map the spatial distribution of contaminants. However, the possibility of an undetected hotspot remains, even when probabilistic modelling and a secondary phase of validatory sampling are employed. This together with the large number of samples required may preclude the commercial use of geostatistics in the remediation of contaminated land.     

Partitioning and Utilization of Carbon and Nitrogen for Dry Matter and Protein Production in Chickpea (Cicer arietinum L.)

The partitioning of N and utilization of C in various processesin chickpea (Cicer arielinum L.) was studied at 10 d intervalsfrom 35 to 135 d after sowing (DAS). Dry matter, C and N contentof the plant increased throughout the study period. The maximumamounts of C and N were fixed during the flowering and earlyfruiting phase (75–115 DAS) and the minimum during theseed filling phase (115–135 DAS). Efficiency of nitrogenfixation in relation to net C utilization and respiratory outputof the whole plant, nodules and nodulated root, varied widely,but was maximum during 75–115 DAS. The crop experiencedsevere respiratory losses, particularly during the vegetativephase, when 83% of the total fixed C was lost in respiration.The crop produced 54·6 g of glucose units, 2·36g of seed dry matter and 495 mg of seed protein. Possible reasonsfor the poor efficiency of chickpea, in terms of photosynthateutilization for dry matter and protein production are discussed. Key words: Cicer arietinum, C, N, economy     

Effect of Low Temperature, Short Days, Water Stress and Dimethyl Sulphoxide on Frost Tolerance of Brassica juncea, Coss and Czern Var. Prakash

Treatment with low temperature, water stress or dimethyl sulphoxideinduces freeze tolerance in Brassica juncea, Coss and Czern.Short day-light periods for 3 or 6 d have no such effect. Percent ion efflux from leaves appears to be related to freezetolerance as determined by cell or plant survival tests. Increasedactivities of peroxidase and malate dehydrogenase are associatedwith freezing injury. Brassica juncea, freezing, water stress