Although the toxic effect of heavy metals on soil microorganism activity is well known, little is known about the effects on different organism groups. The influence of heavy metal addition on total, bacterial, and fungal activities was therefore studied for up to 60 days in a laboratory experiment using forest soil contaminated with different concentrations of Zn or Cu. The effects of the metals differed between the different activity measurements. During the first week after metal addition, the total activity (respiration rate) decreased by 30% at the highest level of contamination and then remained stable during the 60 days of incubation. The bacterial activity (thymidine incorporation rate) decreased during the first days with the level of metal contamination, resulting in a 90% decrease at the highest level of contamination. Bacterial activity then slowly recovered to values similar to those of the control soil. The recovery was faster when soil pH, which had decreased due to metal addition, was restored to control values by liming. Fungal activity (acetate-in-ergosterol incorporation rate) initially increased with the level of metal contamination, being up to 3 and 7 times higher than that in the control samples during the first week at the highest levels of Zn and Cu addition, respectively. The positive effect of metal addition on fungal activity then decreased, but fungal activity was still higher in contaminated than in control soil after 35 days. This is the first direct evidence that fungal and bacterial activities in soil are differently affected by heavy metals. The different responses of bacteria and fungi to heavy metals were reflected in an increase in the relative fungal/bacterial ratio (estimated using phospholipid fatty acid analysis) with increased metal load.
Solanum insanum L. (Solanaceaeae) is the wild progenitor of common eggplant (S. melongena L.) and is naturally distributed in south and southeast Asia, Madagascar and Mauritius. Despite interest in its potential for eggplant breeding it has not been studied extensively. Solanum insanum has been subjected to various taxonomic treatments, with several discussions and arguments on its delimitation as a species, due to its close similarities with the cultivated S. melongena and the wild species S. incanum L. from the Middle East and northern Africa. Solanum insanum has long been used in a variety of medicinal and culinary preparations across many different Asian ethnolinguistic groups. Limited studies carried out on its chemical composition and pharmacognostical properties coupled with ethnobotanic studies reveal that S. insanum has potential for eggplant improvement with respect to phytochemical properties of interest for human health. Further study of morphological and genetic diversity in S. insanum is essential to promote its utilization in eggplant breeding, in light of its potential to hybridize with cultivated eggplant successfully. Here we compile and review the taxonomy, phytogeography, ecology and habitat characteristics, cytology, ethnobotany, breeding and phytochemical analysis of S. insanum. A comprehensive botanical description and illustrations for S. insanum are provided. A detailed comparison of S. insanum and its closely allied species, S. melongena and S. incanum is also made. The potential of S. insanum for crop improvement and future research priorities are discussed.
Pot and field studies were undertaken to assess the substitutability of triple superphosphate (TSP) by a phosphorus (P) fertilizer mixture (PFM) comprising TSP, rock phosphate (RP), and P-solubilizing bacterial inoculants for wetland rice. Six single and two dual inoculants were formulated with Enterobactor gegovie and five Bacillus species and tested in pot and field experiments. Soil-available P and tissue P contents were analyzed, and yield data were recorded. In the pot experiment, the dual inoculant containing E. gegovie + B. mycoides and the single inoculant B. subtilis increased yields by 32% and 25%, respectively, over the TSP control. Under field conditions, E. gegovie + B. subtilis, and E. gegovie + B. pumilus increased grain yield by 22-27% over the TSP control (574 g m −2 ). Results revealed that 50% of TSP could be substituted with RP along with seed inoculants formulated with E. gegovie, B. pumilus, and B. subtilis under tested conditions.
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