University of Hamburg

About: University of Hamburg is a education organization based out in Hamburg, Germany. It is known for research contribution in the topics: Population & Laser. The organization has 45564 authors who have published 89286 publications receiving 2850161 citations. The organization is also known as: Hamburg University.

Soil and plant specific effects on bacterial community composition in the rhizosphere

Abstract: Eubacterial community structures in the plant rhizosphere were examined with respect to plant species, soil type, and root zone location. Three plant species (chickpea, rape and Sudan grass) were grown in intact cores of three California soils (a sandy soil, a sandy loam, and a clay) and were provided with a complete fertilizer solution with or without nitrogen supplied as ammonium nitrate. After 7.5 weeks, the plants were harvested and DNA was extracted from soil adhering to the root tips and from mature root zones at the sites of lateral root emergence. Eubacterial community structures were examined by PCR-DGGE of 16S rDNA to determine the relative abundance and species diversity. While both soil type and nitrogen fertilization affected plant growth, canonical correspondence analyses showed that nitrogen had no significant effect on eubacterial community structures. Eubacterial species diversity was higher in the mature root zones than at the root tips in the sandy soil and the clay but not in the loamy sand. Monte Carlo permutation tests indicated that plant species, root zone and soil type as well as the interactions between these variables had significant effects on community structure. The bacterial rhizosphere community of chickpea was influenced primarily by soil type, whereas root zone was less important. In contrast to chickpea, the community in the rhizosphere of rape and Sudan grass was more affected by the root zone than the soil type. In the sandy soil and the loamy sand, the eubacterial rhizosphere community structure was more affected by the root zone than the plant species and the three plant species had distinct communities. In the clay however, the root zone was less important than the plant species and the rhizosphere communities of chickpea differed from those of rape and Sudan grass. It is concluded that the bacterial community composition in the rhizosphere is affected by a complex interaction between soil type, plant species and root zone location.

In Praise of Convergent Thinking

Abstract: Free production of variability through unfettered divergent thinking holds out the seductive promise of effortless creativity but runs the risk of generating only quasicreativity or pseudocreativity if it is not adapted to reality. Therefore, creative thinking seems to involve 2 components: generation of novelty (via divergent thinking) and evaluation of the novelty (via convergent thinking). In the area of convergent thinking, knowledge is of particular importance: It is a source of ideas, suggests pathways to solutions, and provides criteria of effectiveness and novelty. The way in which the 2 kinds of thinking work together can be understood in terms of thinking styles or of phases in the generation of creative products. In practical situations, divergent thinking without convergent thinking can cause a variety of problems including reckless change. Nonetheless, care must be exercised by those who sing the praises of convergent thinking: Both too little and too much is bad for creativity.