End of day harvest extends shelf life

Baby salad leaves of salad roquette, arugula in the U.S. (Eruca vesicaria ssp. sativa) had an increased postharvest shelf life of 2 to 6 days, while lollo rosso lettuce (Lactuca sativa L. 'Ravita') and red chard [Beta vulgaris L. var. flavescens (Lam.) Lam] baby salad leaves had increased shelf life of 1 to 2 days when harvested at the end of the day compared with leaves harvested at the start of the day. We have shown that improved shelf life of salad roquette and lollo rosso following end-of-day harvest was correlated with altered biophysical characteristics of the cell walls, with increased cell wall extensibility (percent plasticity and elasticity) measured at end of day. Leaf turgor pressure (P, MPa) was also highest in salad roquette and red chard at the end of day. Improved shelf life following 'end of day' harvest was also associated with the accumulation of leaf sucrose in salad roquette but not lollo rosso and red chard following daily photosynthesis. Diurnal alterations of leaf starch concentration were detected in lollo rosso and red chard but not in salad roquette. The degree of leaf shelf life extension in salad roquette and red chard was further associated with the peak rates of leaf photosynthetic activity. These data suggest that, depending on species, significant improvements to postharvest shelf life could be achieved through the rescheduling of time of day for harvest and also provide relevant information on the selection of traits for future genetic improvement.