Adriana E. Lenardis

Response of winter crops differing in grain yield and essential oil production to some agronomic practices and environmental gradient in the Rolling Pampa, Argentina

Abstract Intensive land use in the Rolling Pampa of Argentina generates heterogeneous environmental and ecological conditions associated with agronomic practices. The yields of crops with different resource allocation to the production of primary or secondary metabolites could vary with the environment. Crops that mainly produce primary metabolites would have high yields under favorable environments, and crops that produce high quantities of secondary metabolites would have high essential oil yield under unfavorable environments. To test whether this hypothesis is applicable under the Rolling Pampa conditions, field experiments were conducted with the following objectives: (1) to compare biomass and grain yield in three winter crops: wheat (Triticum aestivum L.), coriander (Coriandrum sativum L.) landrace with high essential oil content (HEO) and coriander landrace with low essential oil content (LEO), grown at different levels of N fertilization and weed control; and (2) to determine relative changes in grain yield, essential oil production and harvest index with environment in the coriander landraces. The crops were grown at two locations differing in physical and chemical soil degradation due to the intensity of land use. Wheat allocated resources mainly to the production of primary metabolites, producing higher biomass and grain yield in the favorable environments. The HEO coriander landrace, which allocates resources to the production of both primary and secondary metabolites, produced similar biomass and grain yield in both locations, but resource partitioning to the production of essential oils was high under unfavorable environmental conditions. The LEO coriander landrace which allocates resources mainly to the production of primary metabolites and, in a minor proportion, to secondary metabolites, produced high biomass and grain yield in intermediate environments and high essential oil yield under unfavorable environments. The environmental conditions of the Rolling Pampa that curtailed the allocation of resources to the production of grain yield promoted the production of essential oils. Based on these results, under poor soil environments, one option is to produce crops with essential oils as marketable yields, instead of adding inputs to improve soil condition and produce traditional crops, where yield is very sensitive to environmental variations.

Response of Coriander (Coriandrum sativum L.) to Nitrogen Availability

ABSTRACT A greenhouse hydroponics system was used to analyze biomass partitioning between primary and secondary metabolites in coriander at different levels of nitrogen availability and a field fertilization experiment was used to evaluate the response of coriander to supplemental nitrogen. Resource partitioning in an Argentinian land-race between primary and secondary metabolites at different levels of nitrogen treatment was asymptotic for biomass, fruit yield, and essential oil production. In a European land-race, resource partitioning was asymptotic to nitrogen treatment for biomass and fruit yield, but parabolic for essential oil production. The response to nitrogen was related to genotypic characteristics of the two land-races and suggest that relatively high levels of nitrogen fertilizer should be used in production of Argentinian land-race coriander and relatively moderate levels of nitrogen fertilizer should be used in production of European land-race coriander.

Arthropod Assemblage Related to Volatile Cues in Flowering Wheat: Interaction between Aphid Herbivory and Soil Conditions as Induction Factors

ABSTRACT Volatile cues released by plants play an important role in plant-insect interactions and are influenced by pests or soil conditions affecting plant metabolism. Field microcosm experiments were used to characterize arthropod spontaneous assemblies in homogenous unstressed wheat patches exposed to volatile cues coming from wheat plants with different levels of stress. The design was a factorial completely randomized block design with three replications. Source wheat pots combined two stress factors: 1) soil degradation level: high and low, and 2) aphid herbivory: with (A) and without (B). Eighteen experimental units consisted of source stressed wheat pots, connected by tubes conducting the volatile cues to sink wheat patches. These patches were located at the end of the tubes placed in a flowering wheat field. Arthropod assemblies on wheat sinks were different between years and they were associated to the source cues. Soil condition was the main discriminating factor among arthropods when a clear contrast between high and low soil degradation was observed, whereas aphid herbivory was the main discriminating factor when soil condition effects were absent. Main soil properties related with arthropods assembly were Mg and K in the first year and cation exchange capacity, total nitrogen, and pH in the second year of experiment. According to this study, spontaneous arthropod distributions in the homogeneous, unstressed wheat patch responded to the volatile cues coming from wheat sources growing in particular soil conditions. It is possible to suggest that soil-plant-herbivore interactions change wheat cues and this phenomenon produces significant differences in neighboring arthropod community structure.