The influence of agronomic factors on the visual quality of field-grown, minimally-processed lettuce

Abstract

SummaryThe effects of nitrogen (N) application, irrigation method, stage of crop maturity, potassium:nitrogen (K:N) ratio, and calcium (Ca) application on post-harvest discolouration of cut Iceberg lettuce (Lactuca sativa cv. Saladin) were investigated in field experiments. Discolouration was scored to provide quantitative measures of both the “pinking” and “browning” of leaf tissue. The majority of the discolouration observed was “pinking” rather than “browning”. The degree of “pinking” or “browning” was affected by the time of transplanting, but not by N application or by irrigation method. Effects of the K:N ratio on leaf discolouration were inconsistent, and can probably be discounted, but Ca application did appear to reduce discolouration at low K:N ratios. Increasing head maturity increased “pinking”. It seems unlikely that agronomic factors have a major impact on the discolouration of cut lettuce. Parallels are drawn with DNA microarray experiments in Arabidopsis thaliana, where changes in the expression of genes encoding key enzymes involved in oxidative discolouration were induced more by environmental stresses than by agronomic factors.