Effects of Plant Age and Rock Phosphate on Quality and Nutrient Release of Legume Residue

An incubation experiment was carried out on plateau and slope fields to investigate the effect of plant age and rock phosphate （RP） on the organic resource （OR） quality and available N and P release of the legume residues, including standing biomass and surface litter. The legumes, Mueuna pruriens （L.） and Lablab purpureus （L.）, were treated with or without Togo rock phosphate （RP） and were sampled at 12, 18, 24 and 30 weeks after planting. Results showed that the application of RP significantly affected the P content of the legume residues on the plateau field for the first 18 weeks, but not the other OR quality parameters, nor their N mineralization, or P release parameters. Although application of RP led to higher P contents in both legumes on the plateau field, the P contents were still far below those observed on the slope field. For both species, the biomass age appeared to have a major impact on their N, P, and polyphenol contents, but not on the liguin content. At 24 weeks, both legume N and P contents dropped to about half their values at 12 weeks of age. Residue age also significantly affected N mineralization both with and without RP addition and the net Olsen-P with RP addition. The younger residues generally led to higher N mineralization and net Olsen-P content than the older residues. The best immediate responses to herbaceous legume addition were expected from younger materials, but often at the cost of the total biomass produced and the possibility to produce seeds. The production of seeds, however, could be potentially implemented on a small area of legumes, thus invariably allowing for maturity and seed production.

Plant responses to variable timing of aboveground clipping and belowground herbivory depend on plant age

Aims Plants use different types of responses such as tolerance and induced defense to mitigate the effects of herbivores.The direc-tion and magnitude of both these plant responses can vary with plant age.However,most studies have focused on aboveground herbivory,whereas important feeding occurs belowground.Here,we tested the hypothesis that plant tolerance and defense following shoot damage or root herbivory depends on plant age.Methods In order to test our hypothesis,we exposed the perennial grass spe-cies Holcus lanatus to defoliation and root nematode inoculation at three growth stages(young,intermediate and old plants),and exam-ined responses of plant traits related to tolerance(regrowth follow-ing defoliation)and defense(leaf and root nitrogen and phenolics).Important Findings Defoliation overall reduced plant shoot and root biomass as well as foliar concentrations of phenolics regardless of plant age at defoli-ation.In contrast,defoliation increased foliar N concentrations,but only when defoliation occurred at intermediate and old plant age.Inoculation with root-feeding nematodes reduced root N concentra-tions after a prolonged period of growth,but only when nematodes had been inoculated when plants were young.The relative shoot re-growth rate of plants increased immediately after defoliation but this was independent of the plant age at which defoliation occurred,i.e.was not stronger in plants that were defoliated at a more advanced age,as hypothesized.Similarly,relative root growth rates increased shortly after defoliation,but this was only observed for plants defoli-ated when they were young.We conclude that plant responses to aboveground and belowground herbivory in traits related to both defense and tolerance are affected by plant age,but do not gener-ally change with plant age.

Bolting and Flowering Response of <i>Lactuca georgica</i>, a Wild Lettuce Relative, to Low Temperatures

To learn about the phenological adaptation of Lactuca georgica Grossh., a wild relative of domesticated lettuce, we studied seed sampled accessions obtained from individual plants at 19 locations throughout six regions in Armenia, and from two natural populations in Dagestan (Russian Federation) collected as bulk samples. The effects of various vernalization treatments on time to bolting, flowering and seed production time were investigated during four successive years at different growth stages of L. georgica plants. We demonstrate that low temperatures play a major role in stimulating the reproduction process of L. georgica plants. Our results would suggest that for L. georgica: 1) There is an obligatory (or nearly so) vernalization requirement;2) Plant age, vernalization duration, and genotype of original sample have a role in bolting and flowering regulation;3) Some plants behaved as typical annuals, responding to vernalization treatment at the seedling stage, but, most did not;4) Four months of vernalization could be adequate to reach bolting in plants with a developed vegetative rosette, for most—but not all—samples;5) In order to find the best solution for stimulating the reproductive process of multiple genotypes, it seems that further study should focus on about 4 - 6 months of vernalization at 4°C applied to plants of about 10 - 22 months old vegetative rosettes, with controlled post-vernalization condition;6) L. georgica germplasm could be used as a source for delayed bolting in breeding of domesticated lettuce varieties.

Evaluation of Regeneration Stock Alternatives for Optimization of Growth and Survival of Field-Grown Forest Trees

Successful reforestation depends on the use of stock material that has a high potential for growth and survival in the environment where it is out-planted. This study is aimed at raising awareness on plant traits that are useful in evaluating the reforestation potential of seedlings and cuttings. The authors reviewed relevant literature on the assessment of quality of seedlings and cuttings and on the comparison of field performance of the two stock types. Results indicated that root-collar diameter, shoot height, root mass, number of first-order lateral roots and shoot-root ratio are morphological parameters whereas root growth potential, water relations, photosynthetic capacity and dormancy status are physiological traits that could be used as a basis for rating and comparing the suitability of seedlings and cuttings for reforestation. There is a discrepancy among studies on the field performance of seedlings and cuttings. It is concluded that a combination of morphological and physiological parameters should be used in evaluating the relative value of cuttings and seedlings. In addition, the age of the parent plant of a cutting should be taken into consideration when comparing the reforestation potential of the two stock alternatives.

DEVELOPMENT OF A MATERIALS RISK INFORMATION PLATFORM FOR A SAFE SOCIETY

A Materials Risk Information Platform is being developed under the cooperation of companies and academic societies with NIMS as project core. To combine safety and economy, which are sometimes contrary to each other, it is important to find an optimal solution using a new concept: risk based engineering. A 5-year project, the Materials Risk Information Platform, was started in 2001 in NIMS on the boilers of thermal power plants and the objectives of this project, research areas and its present state were outlined.