Photomorphogenesis of white clover (Trifolium repens L.) phytochrome mediated effects on 14C-assimilate partitioning

A correct estimation of the amount of biologically fixed atmospheric derived nitrogen (N) is important for evaluating the environmental impact of a clover-grass system. The total-N difference method was compared with the 15N dilution method for estimating biologically fixed nitrogen in a cut and carry clover-grass system managed with three or six cuts per growth season and 0 or 400 kg N ha−1. The two methods were found not to differ statistically. However, as fertilizer recovery must be identical for grass in monoculture and in a clover-grass system in order to get identical estimations of biologically fixed nitrogen when using the two methods, it was indicated that under a high N regime the total-N difference method underestimated the amount of fixed N in the harvested clover material by up to 33%. The choice of method will depend on the environmental conditions and the purpose of the experiment, as well as the resources available. Three sinks of biologically fixed nitrogen were identified: firs...

Estimation of Biological N2 Fixation in a Clover-Grass System by the 15N Dilution Method and the Total-N Difference Method

(1986). Potential for Rhizobium Improvement. Critical Reviews in Biotechnology: Vol. 4, No. 1, pp. 1-74.

Potential for Rhizobium Improvement

Crop and weed competition studies rarely determine how plant-to-plant interactions alter the structure and physiology of crop roots. Soybean has the ability to detect neighboring weeds and to alter growth patterns including the allocation of resources to root growth. In this study, we hypothesized that low red : far red light ratio (R : FR) reflected from aboveground vegetative tissue of neighboring weeds would alter soybean root morphology and reduce root biomass and nodule number. All experiments were conducted under controlled conditions in which resources of light, water, and nutrients were nonlimiting. Low R : FR reflected from aboveground neighboring weeds reduced soybean seedling root length, surface area, and volume, including the number of nodules per plant. An accumulation of H2O2, an increase in malondialdehyde (MDA) content, a reduction in flavonoid content, and a decrease in 1,1-diphenyl-2-picrylhydrazyl (DPPH)–radicle scavenging activity were observed. The reduction in flavonoid con...

https://bioone.org/journals/weed-science/volume-63/issue-4/WS-D-15-00039.1/Detection-of-Neighboring-Weeds-Alters-Soybean-Seedling-Roots-and-Nodulation/10.1614/WS-D-15-00039.1.pdf

Detection of Neighboring Weeds Alters Soybean Seedling Roots and Nodulation

Micropropagated plants ofLeucaena leucocephala nodulated with Rhizobium during thein vitro hardening stage, grew well on N-free-substrate. This is the first report ofin vitro nodulation of micropropagated plants by Rhizobium.

In vitro nodulation of micropropagated plants of Leucaena leucocephala by Rhizobium

The possibilities of using light quality treatments to gain an understanding of the mechanisms controlling the allocation of photosynthate for symbiotic nitrogen fixation were studied. White clover (Trifolium repens) plants were grown at the same photon irradiance in red, blue and green light treatments. Growth, nodulation and the carbon/nitrogen economies of the plants were measured. Both photosynthetic rates per unit leaf area and shoot-root ratios were affected by the treatments. However, the carbon/nitrogen economies of the plants and the fraction of the total plant weight allocated to nodule growth were unaffected.

J. E. Sheehy

Papers

Light quality, symbiotic nitrogen fixation and growth in white clover plants