Characterization and the effect of maturity at harvest on the phenolic and carotenoid content of Northeast USA Apricot (Prunus armeniaca) varieties.

The phenolic and carotenoid content and quality indices of five Northeast apricot varieties were assessed over two years and the impact of maturity at harvest was evaluated. Four varieties were analyzed at commercial and tree ripe stages and one variety after storage for 4 weeks (0-1 °C, 90-95% relative humidity). Total phenolic content ranged from 44.0 to 345.1 mg/100 g, total antioxidant capacity (oxygen radical absorbance capacity assay) from 2096.9 to 7165.1 µmol/100 g, and total carotenoid content from 1312.1 to 7371.1 µg/100, fresh weight. 'Hargrand' apricot had the highest phenolic and carotenoid content. Catechin, chlorogenic acid, and neochlorogenic acid were the predominant phenolic compounds and ß-carotene was the predominant carotenoid compound. Carotenoid content increased with ripening and postharvest storage while changes in phenolic content and antioxidant capacity were variety-dependent. Results show the apricot varieties studied to be good or excellent sources of vitamin A despite moderate carotenoid content attributed to cultivation in a colder climate.

Root distribution and demography in an avocado (Persea americana) orchard under groundcover management systems.

The effect of groundcover management systems on root demography and distribution of newly planted avocado (Persea americana Mill) trees was examined using minirhizotron techniques. We evaluated three groundcover systems: (1) bare soil (BS), pre- and post-emergence herbicides; (2) vegetation strip (VS), post-emergence herbicide applied in a 1-m wide strip centred on the tree row plus a groundcover mixture seeded between tree rows; and (3) complete groundcover (GC), covering the entire surface of the plots. Root production was higher in the non-bearing year (2009-10) than in the bearing year (2010-11). Trees in the BS plots had more roots of bigger diameter in the top 30cm of soil and trees in VS and GC plots had more roots in the 30-60cm depth and of smaller diameter. Lifespan of spring-born roots were 61 and 59% greater than those born during autumn and summer, respectively and soil depth and root diameter were positively correlated with root longevity. Lifespan of thinner roots (<0.2mm) in the BS and VS plots were 49 and 33% greater than GC respectively. Avocado trees grown in contrasting condition compared with their native habitat show high morphological root plasticity, in response to resource and non-resource competition when grown in mixed stands.

A Simple Equation for Predicting Preferential Flow Solute Concentrations.

The transport of pesticides and other chemicals through macropores has been widely observed and predicting it is a challenge. This article considers a simplified two-layer model, similar to overland flow models in which the processes of adsorption and desorption are separated. For the layer near the surface, or the mixing layer, the solute concentration in the layer is equal to that in the percolating water (including preferentially moving water). In the lower profile, the flow is partitioned between matrix and preferential flow. The solute concentration of the matrix flow is characterized by the soil condition near the outlet point, whereas the preferential flow is represented by the solute concentration in the mixing layer. The closed form equation, exhibiting exponentially decreasing macropore flow solute concentrations, is tested against solute breakthrough curves using three independent sets of experimental data. The predicted depths of mixing between 5 and 25 cm are physically realistic and the closed form is shown to reproduce the form of experimental data, particularly under conditions of significant macropore flow. Although highly simplified, the physically based model yields a framework for predicting solute concentration for preferentially moving water.