RESUMO
Bell pepper fruits (Capsicum annuum L.) are prone to both physiological and pathological deterioration following harvest, primarily due to their high metabolic activity and water content. The storage of bell peppers presents several challenges, including weight loss, softening, alterations in fruit metabolites and color, increased decay, and a decline in marketability. The application of edible coatings (ECs) is one of the environmentally friendly technologies that improves many post-harvest quantitative and qualitative characteristics of products. This research investigated the impact of different levels of gum tragacanth (GT) coating (0, 0.25, 0.5, 1, and 2%) on the physiological and biochemical traits of stored bell pepper fruits (BPFs) (8 ± 1°C, 90-95% RH) for 28 days. The results showed the positive effect of coating treatments with higher concentrations of GT, up to 1%. Increasing the concentration of GT to 2% decreased the marketability and quality characteristics of fruits compared to 1% GT. After storage, the physiological weight loss of the fruits treated with 1% GT (10.46%) was lower than that of the uncoated fruits (18.92%). Furthermore, the coated fruits (1% GT) had more firmness, total phenol content, ascorbic acid, and titratable acidity content than uncoated fruits during storage. At the end of storage, the coated BPFs with 1% GT showed higher SOD (97.02 U g-1), CAT (24.38 U g-1) and POD (0.11 U g-1) activities and antioxidant capacity (81.74%) as compared to other treatments. Total soluble solids, total carbohydrates, total carotenoids, pH, malondialdehyde, and electrolyte leakage content increased in coated fruit during storage but were significantly lower than in uncoated fruits. Moreover, the samples coated with GT (1%) maintained good marketability (about 75%), while the marketability of the control (about 40%) was unacceptable. The study shows that GT (1%) coating can be a promising novel treatment option for increasing the storage quality of BPFs.
RESUMO
Melatonin is a growth regulator that improves the growth and chlorophyll (chl) content in plants. This study aims to investigate the effect of melatonin pretreatment on chl synthesis and fluorescence parameters in Malva parviflora exposed to cadmium (Cd). The 42-day-old plants were transferred to nutrient solutions containing 50 µM melatonin. After two days, some plants were exposed to 50 µM Cd. Eight days after Cd treatment, some indicators related to chl fluorescence and some biochemical parameters were measured. In this study, melatonin increased chl content and chl a/pheophytin a (pheo a) ratio, chlorophyllide a (chlide a), porphyrin compounds, and 5-aminolevulinic acid (5-ALA) in the presence of Cd. However, it decreased chl a/chlide a ratio under these conditions. Whereas Cd treatment resulted in significant reductions in photochemical activity and electron transfer rate in PSII, melatonin improved photochemical efficiency of PSII by reducing the toxic effect of Cd on the activity of the oxygen evolving complex (OEC) on the electron donor site and reducing non-photochemical quenching (NPQ). Based on the results, it appears that melatonin can maintain the chl content of plants exposed to Cd by increasing the precursors of the chl biosynthesis pathway and reducing its degradation rate. These results may, at least in our experimental conditions, partly explain the reason for the improved yield and growth of Cd-exposed plants when pretreated with melatonin.