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The results suggest that chitosan coating has the potential to extend the storage life of pomegranate arils by reducing the microbial population on their surface.

The effect of three different coatings; resin wax (Britex Ti), carnauba wax (Xedasol M14), and chitosan (1 and 2 % w/v) on postharvest quality of pomegranate fruits were investigated. Fruits quality characteristics and bioactive compounds were evaluated during 40, 80 and 120 days storage at 4.5°C and 3 additional days at 20°C. The results showed that uncoated fruits showed higher respiration rate, weight loss, L* and b* values of arils, total soluble solids (TSS)/titratable acidity (TA), and pH than coated fruits during storage. Coating treatments could delay declining TSS and TA percent, a* value of arils, as well as bioactive compounds such as total phenolics, flavonoids and anthocyanins content and antioxidant activity. The coated fruits with commercial resin and carnauba waxes showed significantly lower respiration rate and weight loss than other treatments, however carnauba wax could maintain considerably higher fruits quality and bioactive compounds than other coating treatments. The results suggested that postharvest application of carnauba wax have a potential to extend storage life of pomegranate fruits by reducing respiration rate, water loss and maintaining fruit quality.

Silicon application can improve productivity outcomes for salt stressed plants. Here, we describe how strawberry plants respond to treatments including various combinations of salt stress and nano-silicon dioxide, and assess whether nano-silicon dioxide improves strawberry plant tolerance to salt stress. Strawberry plants were treated with salt (0, 25 or 50 mM NaCl), and the nano-silicon dioxide treatments were applied to the strawberry plants before (0, 50 and 100 mg L−1) or after (0 and 50 mg L−1) flowering. The salt stress treatments reduced plant biomass, chlorophyll content, and leaf relative water content (RWC) as expected. Relative to control (no NaCl) plants the salt treated plants had 10% lower membrane stability index (MSI), 81% greater proline content, and 54% greater cuticular transpiration; as well as increased canopy temperature and changes in the structure of the epicuticular wax layer. The plants treated with nano-silicon dioxide were better able to maintain epicuticular wax structure, chlorophyll content, and carotenoid content and accumulated less proline relative to plants treated only with salt and no nano-silicon dioxide. Analysis of scanning electron microscopic (SEM) images revealed that the salt treatments resulted in changes in epicuticular wax type and thickness, and that the application of nano-silicon dioxide suppressed the adverse effects of salinity on the epicuticular wax layer. Nano-silicon dioxide treated salt stressed plants had increased irregular (smoother) crystal wax deposits in their epicuticular layer. Together these observations indicate that application of nano-silicon dioxide can limit the adverse anatomical and biochemical changes related to salt stress impacts on strawberry plants and that this is, in part, associated with epicuticular wax deposition.

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The effects of chitosan coating on extending postharvest life of loquat (Eriobotrya japonica) fruits and maintaining their quality were investigated. Fruits were treated 0, 0.25, 0.5, 0.75, and 1.0% (w/v) chitosan and then stored at 7 with 88 ± 2% relative humidity for 28 days. Browning index, weight loss, total soluble solids (TSS), titratable acidity (TA), vitamin C, phenolic compounds, total polyphenols, and antioxidant activity in fruits were measured. The chitosan coating significantly reduced weight loss and suppressed flesh browning of fruits during cold storage as compared to control and the most effective chitosan concentration was 0.75%. The storage for 28 days at 7 significantly increased TSS, TSS/TA ratio, pH, and vitamin C. However, the fruits treaded with 0.75 and 1.0% chitosan exhibited the higher values of those. Chitosan coating also induced total polyphenol and phenolic compounds such as catachin and quercetin and maintained antioxidant capacity in fruits during cold storage. Overall, the results demonstrated that the chitosan coating followed by cold storage significantly extended fruit storage life and maintained the quality.Additional key words: antioxidant activity, ascorbic acid, browning index, flavonoids, phenolics, storage life Hort. Environ. Biotechnol. 52(1):40-45. 2011.

The role of postharvest application of putrescine (PUT) alone or in combination with chitosan (CH) on maintaining quality of fresh table grapes (Vitis vinifera) cultivar “Shahroudi” was investigated. The clusters were dipped in an aqueous solution containing different concentrations of PUT (0, 1 and 2 mM). Following PUT treatments, some fruits were coated with 1% w/v CH. After treatment, fruits were stored at 0 ± 1C and 90 ± 5% relative humidity for 60 days and 5 additional days in evaluation room. The general appearance of rachis and berries and some physiological characters were estimated. The combination of 1 mM PUT and 1% CH reduced the weight loss, decay incidence, browning, and berry shattering and cracking. Postharvest PUT‐treated berries (1 and 2 mM) exhibited higher total phenolic content, catechin, total quercetin and antioxidant activity and the lower quercetin 3‐galactoside as compared with other treatments. PRACTICAL APPLICATIONS Table grape is a nonclimacteric fruit with a low physiological activity, but is subject to serious physiological disorders, water loss and fungal deterioration during postharvest handling. Stem browning and gray mold infection caused by the fungus Botrytis cinerea are the two main factors which reduce table grape postharvest quality. Recently, biologically active natural products have started to become an effective alternative to synthetic fungicides in maintaining fruit quality during storage. Chitosan coating has been reported to enhance disease resistance against many fungal diseases, when applied as either a preharvest or postharvest treatment. Polyamines (PAs) are also biological compounds with low molecular weight that are ubiquitous in living organisms. PAs have been reported as anti‐senescence agents, the main effects in fruits being retarded color changes, increased fruit firmness, delayed ethylene and respiration rate emissions, induced mechanical resistance.

Drought stress is a major factor‐limiting grass growth. The production of reactive oxygen species (ROS) increases under stress conditions and causes cell oxidative damage. This study investigated the effect of sodium nitroprusside [a nitric oxide (NO) donor] treatment on drought stress in two turfgrass species, creeping bentgrass and tall fescue. Physiological characteristics such as relative water content (RWC), ion leakage, chlorophyll and proline content, and activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) were evaluated after 40 d drought stress and in the recovery stage. Results showed that nitric oxide (NO) treatment, especially 150 μm, could maintain significantly higher RWC and reduce ion leakage under drought stress conditions in both species. Furthermore, both turfgrass species showed higher chlorophyll and proline content after drought stress period when sprayed with NO, while chlorophyll and proline content of control plants declined. Drought stress significantly reduced SOD and APX activity, while NO treatment induced higher SOD and APX activity under drought conditions. After recovery, leaf RWC returned to the control level; however, NO‐sprayed plants showed higher RWC compared to controls. Both turfgrass species exhibited lower chlorophyll content at the recovery stage when exposed to severe drought stress, and NO application increased chlorophyll content compared to controls. No significant differences were found between NO treatment and control plants for proline and SOD activity, but APX activity of NO‐sprayed plants was higher than in the control plants. These results suggest that foliar application of NO may alleviate drought stress in turfgrass by maintaining membrane stability and inducing antioxidant enzyme activity.