University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Photosynthesis controls of CO2 efflux from maize rhizosphere

Abstract: The effects of different shading periods of maize plants on rhizosphere respiration and soil organic matter decomposition were investigated by using a 13 C natural abundance and 14 C pulse labeling simultaneously. 13 C was a tracer for total C assimilated by maize during the whole growth period, and 14 C was a tracer for recently assimilated C. CO2 efflux from bare soil was 4 times less than the total CO2 efflux from planted soil under normal lighting. Comparing to the normal lighting control (12/12 h day/night), eight days with reduced photosynthesis (12/36 h day/night period) and strongly reduced photosynthesis (12/84 h day/night period) resulted in 39% and 68% decrease of the total CO2 efflux from soil, respectively. The analysis of 13 C natural abundance showed that root-derived CO2 efflux accounted for 82%, 68% and 56% of total CO2 efflux from the planted soil with normal, prolonged and strongly prolonged night periods, respectively. Clear diurnal dynamics of the total CO2 efflux from soil with normal day-night period as well as its strong reduction by prolonged night period indicated tight coupling with plant photosynthetic activity. The light-on events after prolonged dark periods led to increases of root-derived and therefore of total CO2 efflux from soil. Any factor affecting photosynthesis, or substrate supply to roots and rhizosphere microorganisms, is an important determinant of root-derived CO2 efflux, and thereby, total CO2 efflux from soils. 14 C labeling of plants before the first light treatment did not show any significant differences in the 14 CO2 respired in the rhizosphere between different dark periods because the assimilate level in the plants was high. Second labeling, conducted after prolonged night phases, showed higher contribution of recently assimilated C ( 14 C) to the root-derived CO2 efflux by shaded plants. Results from 13 C natural abundance showed that the cultivation of maize on Chromic Luvisol decreased soil organic matter (SOM) mineralization compared to unplanted soil (negative priming effect). A more important finding is the observed tight coupling of the negative rhizosphere effect on SOM decomposition with photosynthesis.

Impact of Interpopulation Divergence on Additive and Dominance Variance in Hybrid Populations

Abstract: We present a theoretical proof that the ratio of the dominance vs . the additive variance decreases with increasing genetic divergence between two populations. While the dominance variance is the major component of the variance due to specific combining ability ( \(\mathrm{{\sigma}}_{\mathrm{SCA}}^{2}\) ), the additive variance is the major component of the variance due to general combining ability ( \(\mathrm{{\sigma}}_{\mathrm{GCA}}^{2}\) ). Therefore, we conclude that interpopulation improvement becomes more efficient with divergent than with genetically similar heterotic groups, because performance of superior hybrids can be predicted on the basis of general combining ability effects.

Studies on antioxidant activities of mucuna seed (Mucuna pruriens var utilis) extract and various non-protein amino/imino acids through in vitro models

Abstract: The antioxidant activities of a methanolic extract of mucuna beans (Mucuna pruriens var utilis) and several non-protein amino/imino acids, namely L-3,4-dihydroxyphenylalanine (L-dopa), L-3-carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (compound I), (−)-1-methyl-3-carboxy-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (compound II) and 5-hydroxytryptophan (5-HTP), were evaluated. By virtue of their hydrogen-donating ability, all the tested compounds and the mucuna seed extract showed excellent reducing power, with the highest values being recorded for L-dopa in a dose-dependent manner. Similarly, as compared with synthetic antioxidants (BHT and BHA) and quercetin, all the tested compounds and the seed extract were found to be more potent in free radical-scavenging activity (P < 0.05) against α,α-diphenyl-β-picrylhydrazyl (DPPH•) radicals. Hydroxyl radicals (OH•) and superoxide anion radicals (O2•−) were effectively scavenged by the tested compounds, with the exception that no scavenging activity of 5-HTP was observed on (O2•−) up to a concentration of 2 mg ml−1, as was also the case for BHA. Among the tested non-protein amino/imino acids and seed extract the highest peroxidation-inhibiting activity (95%) was recorded for 5-HTP. On the other hand, in the linoleic acid/β-carotene-bleaching system, L-dopa, compound I and compound II acted as pro-oxidants, whereas the seed extract showed only weak antioxidant activity as in the linoleic acid emulsion system. Copyright © 2003 Society of Chemical Industry