Effect of cold storage on stomatal functionality, water relations and flower performance in cut roses

Symptoms of water stress are the most frequent cause for the “end of vase life” in prior stored roses. It was hypothesized that dark storage may alter the stomatal functionality and may cause water balance problems during the subsequent vase life period. The effect of short- and long-term storage on functionality of stomatal and subsequent flower performance was investigated in two rose cultivars (cvs) (‘Akito’ and ‘Grand Prix’) with presumed different sensitivity for development of water stress symptoms during the vase life. Compared to no storage, both short term storage (2.3 d at 6 °C) and long term storage (28 d at 0.5 °C) negatively affected the stomatal functionality in cultivar (cv) Akito. Stomatal functionality parameters such as the rapidity of the closing response upon dehydration and the relative water content at which stomata are fully closed showed good correlations with flower performance parameters (flower weight changes and vase life). This indicates that in cv Akito, the decreased stomatal functionality is one of the factors involved in the poor vase life of prior stored flowers. In cv Grand Prix, however, storage did not greatly affect the stomatal functionality but storage negatively affected flower performance in a comparable way as in cv Akito. A pre-treatment with abscisic acid prior to storage slightly improved stomatal functionality in both cvs, but no clear effect on flower performance was observed. Addition of the bactericide 8-HQC to the vase water improved flower performance in both cvs but could not alleviate the negative effect of cold storage on flower performance. Results show that in roses cold storage may, depending on the cultivar, negatively affect stomatal functionality and this may contribute to water stress and ultimately flower failure. In addition, cold storage may negatively affect xylem water conducting properties through processes not related to bacterial contamination.</p

Low oxygen storage improves tomato postharvest cold tolerance, especially for tomatoes cultivated with far-red led light

We investigated the effects of low oxygen storage on chilling injury development, colour development, respiration and H2O2 levels of ‘Merlice’ tomatoes cultivated with and without far red (FR) LED lighting during 20 days of shelf-life. Mature green (MG) and red (R) tomatoes were stored at 2 °C in combination with 0.5, 2.5, 5 and 21 kPa O2 for 15 days (experiment 1). MG tomatoes cultivated under either white LED or white LED light with FR LED light were stored at 2 °C in combination with 1, 5 and 21 O2 kPa for 14 days (experiment 2). Chilled MG and R tomatoes from experiment 1 showed decay, firmness loss and higher weight loss during shelf-life which were reduced under low oxygen conditions. FR during cultivation improved chilling tolerance of MG tomatoes. Fastest colour development and lowest respiration rate during shelf-life were observed for MG fruit cultivated with FR lighting prior to storage at 1 kPa O2/0 kPa CO2. H2O2 levels during the shelf-life were not affected during cold storage. The improved cold tolerance of MG tomatoes cultivated with FR lighting is likely due to lower oxygen uptake that led to both higher lycopene synthesis and less softening

The impact of wounding and postharvest storage conditions on retention of soluble protein in sugar beet leaves

Abstract: Sugar beet leaves can be a viable and economically interesting source of high-quality protein for the food industry. We investigated how storage conditions and leaf wounding at harvest affect the content and quality of the soluble protein. After collection, leaves were either stored intact or shredded to mimic wounding induced by commercial leaf harvesters. Leaf material was stored in small volumes at different temperatures to assess leaf physiology or in larger volumes to assess temperature development at different locations in the bins. Protein degradation was more pronounced at higher storage temperatures. Wounding accelerated the degradation of soluble protein at all temperatures. Both wounding and storage at higher temperatures greatly stimulated respiration activity and heat production. At temperatures below 5°C, ribulose-1,5-biphosphate carboxylase oxygenase (RuBisCO) in intact leaves was preserved for up to 3 weeks. At temperatures of 30–40°C, RuBisCO degradation occurred within 48 h. Degradation was more pronounced in shredded leaves. In 0.8-m3 storage bins at ambient temperature, core temperatures rapidly increased, up to 25°C in intact leaves and up to 45°C in shredded leaves within 2–3 days. Immediate storage at 5°C greatly suppressed the temperature increase in intact but not in shredded leaves. The indirect effect of excessive wounding, that is, heat production, is discussed as the pivotal factor responsible for increased degradation of protein. For optimal retention of soluble protein levels and quality in harvested sugar beet leaves, it is advised to minimize wounding and to store the material at temperatures around −5°C. Practical Application: To preserve the soluble protein content and quality for at least 3 weeks, sugar beet leaves should be harvested with minimal wounding and stored at temperatures between 1 and 5°C. When aiming to store minimally wounded leaves in larger volumes, it must be ensured that the product temperature in the core of the biomass meets the temperature criterium or the cooling strategy must be adjusted. The principles of minimal wounding and low temperature storage are transferable to other leafy crops that are harvested for food protein