Combined Effects of Growth Cycle and Different Levels of Aeration in Nutrient Solution on Productivity, Quality, and Shelf Life of Watercress (Nasturtium officinale R. Br.) Plants

Abstract

The objective of this research was to study the effects of growing cycle (spring vs. winter) and nutrient solution aeration [no aeration (NA), low aeration (LA) or high aeration (HA)] on yield, quality, and on shelf life as a fresh-cut product of watercress grown in a floating system. The growing cycles lasted 25 days in spring and 39 days in winter. In the spring cycle, the plants had significantly higher yield and antioxidant capacity and lower specific leaf area, total root length, root diameter, length of 0 to 0.5 mm diameter root, and oxalate content than in the winter cycle. The absence of aeration increased the antioxidant capacity and vitamin C content in both cycles. Several adventitious roots developed exogenously from the watercress stem at the nodes as a morphological adaptation to oxygen depletion, particularly in NA conditions. The nitrate, oxalate, Ca2+, K+ contents, and microbial populations were affected by both the cycle and the aeration conditions. Hue angle of the leaves was affected by both the cycle and storage time, and chromaticity and lightness were affected by the three factors (cycle, aeration, and storage time). The global quality was significantly higher (7.8 over 9 points hedonic scale) in the spring cycle than in winter, the score reflecting their marketable value (7.0 over 9 points). The mild dehydration problems observed in the winter cycle that led to a slightly lower overall product quality that could be the result of the development of thinner leaves and also the differences in the respiration rates compared with the spring cycle. In general, the spring cycle led to higher productivity, antioxidant capacity, and Ca2+ and K+ contents and lower oxalate content. Aeration slightly affected the quality of the final product, the plants grown in non-aerated conditions being richer in vitamin C and antioxidants and with lower nitrate content.