Climacteric Rise Research Articles

A novel technique for inducing ripening and controlling fungal growth in green bananas using warm tangerine oil vapor and its possible modes of action

The study aimed to develop a novel technique for inducing uniform ripening and preventing fungal growth in green bananas, thereby producing high-quality raw materials for various banana-derived products and reducing industrial fruit losses. Tangerine oil (TO) vapor at concentrations of 100, 200, and 400 μl was introduced into a 1-L chamber containing green bananas. The TO was then heated to 50 °C using a heat pad for 10 min, allowing the vapor to release inside the chamber. The chamber with green bananas was held at 30 °C to allow contact with the TO vapor for 12 h. Subsequently, the bananas were kept at 30 ± 2 °C for 10 days to ripen. The experiment was compared to acetylene and control treatments. TO was also tested to inhibit the growth of Lasiodiplodia theobromae (the cause of crown rot disease in bananas) during storage, and the assessment of banana ripening quality was conducted. The potential mode of action in both ripening acceleration and fungal control was investigated. Results showed that bananas treated with TO vapor at 200 μl and acetylene exhibited an earlier climacteric rise within five days compared to the control (10 days). TO vapor (≥200 μl) demonstrated efficacy against L. theobromae on agar and on the banana surface. TO (200 μl) contributed to improved banana ripening quality, as evidenced by reduced firmness and pH, increased total soluble solids (TSS) and titratable acidity (TA) content, and the absence of mold disease on the surface after ten days. Regarding the mode of action, the peel morphology of bananas treated with TO revealed a large pore size during ripening, affirming the efficiency of TO in accelerating banana ripening, contributing to the acceleration of chlorophyll reduction and the transition to a yellow banana. Limonene, a key component, facilitated cell wall penetration, causing cell membrane leakage in fungi. This finding confirms that implementing this technique for controlling banana ripening in the industry could lead to superior-quality bananas with various beneficial product applications.

Imitation and reinforcement learning to control soft robots: a perspective

It would not be an over-stretch to appraise soft robotics as one of the most sizzling topic in this era, owing to its unparalleled performance in terms of exhibited deformability, soft-interaction and luscious dexterity. In spite of that, we see minimal applications of this class around us. We believe the reason roots in the gap between design and fabrication of the soft robots and the capability to control them. The remedy to this imbalance, we believe, is a necessity for a climacteric rise in the capability to control them. The control, however poses challenges due to virtually infinite degrees of freedom of soft robot design, in terms of modelling the behavior of the robot, modelling its interaction with the environment or the environment’s effect on the robot. These challenges provoke the preponderant need for solutions that either can work with the inaccurate models of the robot obtained or avoid it altogether. To answer what can be used with these limitations we present here two potential classes of algorithms from machine learning capable of performing well under just the listed conditions: reinforcement learning (RL) can provide a solution in the form of a policy to control a platform with sophisticated dynamics even when the presented environment to train said policy has questionable accuracy, while Imitation Learning (IL) trains a policy while avoiding the need of a model or its constituent parts altogether and a policy is learned based on the teachings of an expert.

Effect of Chitosan on Storage Behaviour of Sapota Manilkara achras (Mill) fosberg cv. ‘Kalipatti’

The present study was undertaken to study the effect of chitosan treatments on the storage behaviour of sapota Manilkara achras (Mill) fosberg cv. Kalipatti is stored at ambient temperature. The climacteric rise in sapota fruits shortens the postharvest life and degrades the quality of the fruits. A polysaccharide like a chitosan has been used as an edible coating to extend the storage life of sapota fruits, which is an innovative approach for fruit preservation and sustainable development. Chitosan-based coatings have tremendous potential in several fruits to extend the shelf-life. An investigation was carried out to know the effectiveness of post-harvest treatments with edible coatings (0.5%, 1%, 1.5%, and 2% chitosan) compared with the control. 1% chitosan coating resulted in maximum fruits (more than 75%) having a shelf life of 7 days under ambient condition which was at par with 1.5% chitosan coating. Chitosan coating reduced the physiological losses in weight as compared to the uncoated fruits. The maximum retention of physical parameters such as fruit firmness, specific gravity, colour L*, a* and b* values as well as slow ripening and less spoilage behaviour was observed in chitosan-coated sapota fruits.

Xylem Functionality Is Not a Direct Indicator of Apple Preharvest Fruit Drop

Apple (Malus ×domestica) growers can incur significant economic losses when fruit drop before they can be harvested [preharvest fruit drop (PFD)]. In some years and cultivars, more than 30% of potential yield can be lost. Growers frequently apply plant bioregulators to reduce PFD, either via delay in maturity [aminoethoxyvinylglycine (AVG), 1-methylcycolpropene] or via inhibition in production of cell hydrolysis enzymes in the fruit pedicel [naphthalene acetic acid (NAA)]. Finding a physiological indicator of PFD would allow growers to assess the susceptibility of fruit to PFD. Due to its lignification, xylem is believed to be the last tissue to break down in the fruit pedicel, leading to PFD. To determine whether loss in xylem functionality can be used as an indicator of PFD potential, studies were conducted in 2020 and 2021 with ‘Red Delicious’ treated with AVG (132 µL·L−1), NAA (10 µL·L−1), and an ethylene-producing compound [ethephon (150 µL·L−1 in 2020, 200 µL·L−1 in 2021)] to generate a range of PFD potentials. Xylem functionality was assessed in the fruit cortex. Internal ethylene content (IEC), fruit maturity indices, and PFD rates were quantified weekly throughout the harvest period. Expression of genes encoding for cell hydrolysis enzymes (MdEG1 and MdPG2) was quantified to relate xylem functionality to fruit abscission mechanisms. In 2020 and 2021, AVG reduced PFD compared with the untreated control by decreasing IEC. Although ethephon did not result in higher PFD than untreated fruit, NAA reduced PFD in 2020 but not 2021. For all treatments in both years, there was a linear decrease in xylem functionality throughout the measurement period. Cumulative PFD exponentially decreased as xylem functionality neared zero and the climacteric rise in ethylene began. Concurrent with the rise in IEC and PFD was an increase in the expression of MdEG1 and MdPG2 in the fruit pedicel of the control compared with AVG-treated fruit. AVG-treated fruit lost xylem functionality at a similar rate to the untreated control but had lower expression of MdEG1 and MdPG2. These results indicate that xylem functionality is not a sole direct indicator of PFD. The concurrent increase in PFD and expression of MdEG1/MdPG2 supports previous research indicating that these two genes may serve as potential markers for PFD.

Study of Biochemical and Phytochemical Variations in Carica papaya, Linn. During Storage

Papaya is a tropical fruit and is usually harvested prior to the onset of climacteric rise. The moisture content of Papaya is always higher than 70% throughout the season. The moisture content increases significantly with season. The phytochemical analysis of Papaya leaves contain carbohydrates, saponins, terpenoides, alkaloids, phenols, glycosides, cardiac glycosides and flavonoids. Temperature has a major role in the post harvested biochemical changes and the activity of polyphenol oxidase in Papaya. Flesh color development in nonstored fruits did not change significantly during the first six days of storage, and then rapidly increases. Unripe fruit stored for 5 days at above 27 ºC exhibits faster ripening rates. The optimal temperature for storing Papayas are found to be between 21.5 to 25 ºC. Biochemical changes in Papaya fruits at room temperature revealed that the level of phenolics and reducing sugars are gradually increases . But there is a gradual decrease in the protein content of the fruits. As the PPO quality deteriorating enzyme, the nutritional quality was assayed by estimating the activity of PPO. The enzyme was responsible for the browning of Papaya fruits. Post harvest storage of Papaya is a major problem for many farmers. High moisture content of papaya fruit may affect the contamination of disease spreading microbes and insect vectors. They may cause spoilage of soft tissues of Papaya. High temperature storage may cause the nutrient quality of fruit. Many enzymes and proteins degraded in extreme temperature condition.

Biocomposite Coatings Delay Senescence in Stored Diospyros kaki Fruits by Regulating Antioxidant Defence Mechanism and Delaying Cell Wall Degradation

Climacteric rise in the rate of respiration and ethylene production in harvested persimmon (Diospyros kaki) fruits leads to early onset of fruit tissue senescence. Therefore, this study was carried out to maintain the quality of stored persimmons by using edible coatings. For this purpose, Aloe vera gel was combined with food hydrocolloids, gum arabic or tragacanth gum, and applied on persimmon fruits that were stored for 20 days at 20 ± 1 °C and 80–85% RH. Biocomposite coatings, compared to control, remarkably reduced weight loss, decay incidence, respiration rate, ethylene production, electrolyte leakage, malondialdehyde, H2O2 and superoxide anion content in stored fruits. The use of composite coatings inhibited colour change by reducing the accumulation of total carotenoids, maintained higher antioxidative enzymes activity and suppressed the activity of cell wall degrading enzymes, resultantly preserving cell wall components. Composite coated fruits exhibited the least change in biochemical attributes and higher sensory scores in comparison with non-coated fruits at the end of the storage period. In conclusion, Aloe vera gel/gum arabic was the most effective coating treatment before storing persimmons.

Effects of modified sweet potato starch edible coating incorporated with cumin essential oil on storage quality of ‘early crisp’

In this study, an edible formulation consisting of modified sweet potato starch (MSPS) and cumin essential oil (CEO) was developed. The effectiveness of the coating on the physiochemical and sensory traits of ‘early crisp’ stored at 25 °C for 28 d was evaluated. The results showed that incorporation of 0.2–0.4% (v/v) CEO in modified sweet potato starch edible coatings significantly (p<0.05) reduced rot lesion on infected pear caused by Alternaria alternata, in vivo and also delayed changes in fruit color, firmness, and chlorophyll degradation. Coating significantly suppressed the onset of climacteric rise in respiration and minimized the weight loss of the pears. The stomata densities in coated pear were well preserved. Overall, the antifungal edible coating improved the storage quality of the pears and maintained consumable and better sensory quality compared to uncoated samples. The results suggest that modified sweet potato starch enriched with 0.2–0.4% (v/v) cumin essential oil could be useful as a preservation method to address issues of postharvest losses, and agricultural sustainability in the future.

Physiological and Biochemical Response of Tropical Fruits to Hypoxia/Anoxia.

Aerobic respiration and oxygen consumption are indicators of routine metabolic rate, and dissolved oxygen in plant tissues is one of the most important environmental factors affecting their survival. The reduction of available O2 leads to hypoxia which causes a limitation of the oxidative phosphorylation; when O2 is absent, tissues generate ATP by activating the fermentative glycolysis to sustain glycolysis in the absence of mitochondrial respiration, which results in the production of lactate. Overall, hypoxia was reported to often decrease the respiration rate (O2 uptake) and delay the climacteric rise of ethylene in climacteric fruits by inhibiting action, thus delaying their ripening. Much research has been done on the application of postharvest hypoxia and anoxia treatment to temperate fresh crops (controlled or modified atmosphere), however, very few reported on tropical commodities. Indeed, the physiological mode of action of low or absence of oxygen in fresh crops is not well understood; and the physiological and biochemical bases of the effects low or absence of O2 are also yet to be clarified. Recent investigations using omics technologies, however, have provided useful information on the response of fresh fruits and vegetables to this abiotic stress. The aims of this review are to (i) report on the oxygen exchange in the crops tissue, (ii) discuss the metabolic responses to hypoxia and anoxia, and (iii) report the physiological and biochemical responses of crops tissues to these abiotic stresses and the potential benefits of these environmental conditions.

Some important biochemical changes orchestrating flower development and senescence in Nicotiana plumbaginifolia Viv. and Petunia hybrida Vilm. flowers

ABSTRACT A comparative study of some biochemical parameters and expression patterns during flower development and senescence in Nicotiana plumbaginifolia and Petunia hybrida was carried out to ascertain the differences between the two important ornamentals. Lipid peroxidation (LPO) was found to increase throughout flower development and senescence in P. hybrida whereas in N. plumbaginifolia it decreased towards flower opening and showed a sharp increase towards senescence. Membrane stability index showed a marginal decrease towards senescence in the flowers of both the plants. Activities of the antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and lipoxygenase) increased up to the open flower stage (stage IV) and decreased thereafter towards the senescent stage in the flowers from both the plant species. The pre-senescent stages in flowers from both the plants did not show up the detection of ethylene in the petal tissues on gas chromatograph while as a climacteric rise in the ethylene concentration was exhibited by the senescent stages of both the flowers under study. mRNA-transcripts of senescence associated gene DAD1 were found to accumulate in the open flower stage (stage IV) in N. plumbaginifolia and those of ETR1 and SAG12 were found to accumulate in the open flower stage (stage IV) in P. hybrida.

Gene Expression in 1-Methylcyclopropene (1-MCP) Treated Tomatoes during Pre-Climacteric Ripening Suggests Shared Regulation of Methionine Biosynthesis, Ethylene Production and Respiration

The physiology of fruit ripening is defined as either ‘climacteric’ or ‘non-climacteric’. In climacteric fruit respiration during ripening increases until it reaches a peak, which is accompanied by an increase in autocatalytic ethylene production, whereas the respiration of non-climacteric fruit does not increase and they have no requirement for ethylene to complete their ripening. In an attempt to gain further insight into the involvement of autocatalytic ethylene production with the climacteric rise in respiration, tomato fruit were harvested at three defined stages of maturity prior to the climacteric peak (mature green, breaker, and early orange) and immediately exposed to the gaseous molecule 1-methylcyclopropene (1-MCP). The gene expression profile at each of these stages was monitored after 24 h, using an Affymetrix tomato microarray chip. This approach enabled us to identify ethylene responsive genes that are commonly regulated at early stages of ripening, as well as new candidate genes. In addition, 1-MCP treatment affected the levels of metabolites related to methionine biosynthesis. Methionine feeds climacteric ethylene production and we found that promotors of the genes of enzymes that catalyze the production of homoserine and homocysteine (aspartokinase/homoserine dehydrogenases and cystathionine beta lyase, respectively), precursors in the methionine pathway, contain the AtSR1 binding motif. This binding motif is recognized by ethylene activated transcription factors, hence indicating a role for ethylene in methionine synthesis during early ripening, explaining the autocatalytic ethylene production during subsequent ripening stages.

Elucidating the involvement of ethylene and oxidative stress during on- and off-tree ripening of two pear cultivars with different ripening patterns

Scarce information is available about the ripening process of European pears attached and detached from the tree. Accordingly, this study aimed to investigate the physiological and biochemical processes underlying both on- and off-tree fruit ripening in a summer (‘Conference’) vs. a winter (‘Flor d’Hivern’) pear cultivar. For each cultivar, a batch of fruit was harvested at the commercial harvest date and ripened at 20 °C and another batch was left to ripen on the tree. In both cultivars the inability of the fruit to soften on-tree, was related to a very limited ethylene metabolism but also associated to high content of H2O2 and low lipid peroxidation levels. In contrast, ripening in detached fruit was cultivar-dependent. In ‘Conference’ pears, the sharp firmness loss and colour changes observed during off-tree ripening were not strictly associated to an enhanced ethylene production but rather triggered by an oxidative related process preceding the climacteric rise. In contrast, ‘Flor d’Hivern’ pears experienced limited softening and degreening during off-tree ripening not being related to the action of ethylene or oxidative stress. Collectively our results showed that pear ripening was not exclusively dependent of ethylene production and that the fruit potential to limit oxidative damage may be involved with the inability of some European pear cultivars to ripen on-tree.

An alternative technique using ethylene micro-bubble technology to accelerate the ripening of banana fruit

Banana is commercially harvested at the mature green stage, and post-harvest ripening is necessary to increase its marketability and obtain it in its ideal ripened form with the desired color and texture. This study investigated the effectiveness of the ethylene microbubble (C2H4-MBs) technique as an alternative to accelerating the post-harvest ripening of banana (Musa spp.). Bananas commercially harvested at the mature green stage were separated into four groups: (1) dipped in aqueous C2H4-MBs for10 min; (2) dipped in aqueous C2H4-MBs for20 min; (3) fumigated with 1000 mg L−1 of C2H4 gas at 25 °C for 12 h, and (4) allowed to ripen naturally (untreated controls). Treated fruit were stored at 25 °C for 10 d. The C2H4-MBs were successfully generated with a mean diameter of 50 μm, and the size reduced with time. The application of both C2H4-MBs and fumigation hastened the ripening of bananas compared to the untreated controls. The treatment with C2H4-MBs for just 10 min satisfactorily ripened the bananas in a similar manner as the fumigated technique. The treated fruit exhibited earlier climacteric rise in respiration and outburst of C2H4 production, accompanied by a drastic acceleration in chlorophyll degradation and yellowing, fruit softening, and total soluble solids content. Present study demonstrated the efficiency and effectiveness of this alternative post-harvest application of C2H4-MBs to accelerate banana ripening. This innovative technology is convenient and easy to carry out without the complication of airtight and cooling facilities and, thus, has high commercial potential.

The isocitrate dehydrogenase 1 gene is associated with the climacteric response in tomato fruit ripening

Abstract Climacteric ripening is related to a respiratory climax accompanied by an exponential increase in ethylene production. This association is not fully understood. Tomato fruit were exposed to the ethylene antagonist 1-methylcyclopropene (1-MCP) at different ripening stages and their transcriptome was monitored. ISOCITRATE DEHYDROGENASE 1 (ICDH, Solyc01g005560.2.1) was the only respiratory process related gene that was down regulated at all ripening stages including the mature green. Silencing SlICDH1using VIGS (virus indused gene silencing), to about 50 % of its native expression, in Micro-Tom tomatoes, reduced both respiration and ethylene production of the harvested fruit. Silenced SlICDH1 tomatoes also exhibited prolonged ripening and reduced susceptibility to the pathogen Botrytis cinerea. In addition, ethylene response factors binding sites were identified in the promotor and in the first intron of SlICDH1. These results suggest that regulation of SlICDH1 is a key step in the initiation of the climacteric rise of respiration via ethylene regulation.

Respiratory patterns of European pear (Pyrus communis L. ‘Conference’) throughout pre- and post-harvest fruit development

Information on the developmental stage of pear pre-harvest and in shelf-life is crucial to determine the optimum timing of harvest, post-harvest treatment, and time of consumption ensuring high eating quality. In the present study, CO2 emission and fruit quality of European pear (Pyrus communis L.) ‘Conference’ were analysed pre- and post-harvest with emphasis on shelf life for three years. Additionally, cytochrome and cyanide-resistant O2 consumption were analysed in the last year of experiments. The respiration rate of pear showed typical climacteric rise of CO2 emission in two years only, despite daily measurements. However, in each year the fruit quality in shelf life was closely linked to harvest date suggesting climacteric fruit response. Thus, the developmental stage of ‘Conference’ pear should be analysed by additional methods. Particularly, the cytochrome and cyanide-resistant O2 consumption showed an encouraging potential to obtain data on characteristic respiratory patterns.

Influence of fruit maturity, 1-methylcyclopropene (1‑MCP) treatment and storage temperature on ethylene production and firmness of ‘Goldrich’ and ‘Orangered’ apricots

Apricots are climacteric fruits characterized by a fast ripening process after harvest. To avoid fruit quality losses during storage, transport and distribution, fruits are often harvested at an unripe maturity stage, resulting in lower sensory quality and higher heterogeneity of the batches in the supply chain. The aim of this study was to evaluate the influence of two ripening stages at harvest, two storage temperatures (1 and 8°C), and 1-methylcyclopropene (1-MCP) treatment on apricot quality and ethylene production of the cultivars ‘Goldrich’ and ‘Orangered’. Fruit were stored under regular atmosphere (92% relative humidity). During storage and shelf life, firmness was the highest evolving parameter compared to acidity, sugar content and skin colour. The ripening stage of the fruits highly influenced the decrease in firmness during storage. Firmness decrease was 10 to 20% lower for unripe fruits, and no firmness decrease was observed for unripe ‘Orangered’. The same tendencies were observed with ethylene production. Climacteric rise was influenced by the fruit ripening stage and was delayed (5 days) for unripe fruits. Unripe ‘Orangered’ did not produce ethylene; probably due to the non-activation of ethylene biosynthesis genes in unripe fruits. The influence of 1-MCP treatment on firmness change and ethylene production differed depending on the measurement moment: no influence was observed directly after storage, whereas, after 3 days of shelf-life, fruit softening and ethylene production were reduced by using 1-MCP. In contrast, storage temperature highly influenced firmness and ethylene production, exhibiting a 20% higher softening and an earlier (>20 days) climacteric rise at 8°C compared to 1°C for ‘Goldrich’. For ‘Orangered’, ethylene production began after 7 days of storage, independently of the temperature. The interactions between the different influencing factors, as well as potential recommendations for the apricot supply chain actors, are discussed.

Phytochromobilin deficiency impairs sugar metabolism through the regulation of cytokinin and auxin signaling in tomato fruits

Phytochomes and plant hormones have been emerging as important regulators of fleshy fruit biology and quality traits; however, the relevance of phytochrome-hormonal signaling crosstalk in controlling fruit development and metabolism remains elusive. Here, we show that the deficiency in phytochrome chromophore phytochromobilin (PΦB) biosynthesis inhibits sugar accumulation in tomato (Solanum lycopersicum) fruits by transcriptionally downregulating sink- and starch biosynthesis-related enzymes, such as cell-wall invertases, sucrose transporters and ADP-glucose pyrophosphorylases. PΦB deficiency was also shown to repress fruit chloroplast biogenesis, which implicates more limited production of photoassimilates via fruit photosynthesis. Genetic and physiological data revealed the involvement of auxins and cytokinins in mediating the negative impact of PΦB deficiency on fruit sink strength and chloroplast formation. PΦB deficiency was shown to transcriptionally repress type-A TOMATO RESPONSE REGULATORs and AUXIN RESPONSE FACTORs both in pericarp and columella, suggesting active phytochrome-hormonal signaling crosstalk in these tissues. Data also revealed that PΦB deficiency influences fruit ripening by delaying the climacteric rise in ethylene production and signaling. Altogether, the data uncover the impact of phytochromobilin deficiency in fine-tuning sugar metabolism, chloroplast formation and the timing of fruit ripening and also reveal a link between auxins, cytokinins and phytochromes in regulating sugar import and accumulation in fruits.

Nondestructive Apple Ripening Stage Determination Using the Delta Absorbance Meter at Harvest and after Storage

The delta absorbance (DA) meter is a handheld instrument which noninvasively measures the chlorophyll content in fruits. In the present work, it was used to monitor the ripening process linked to the climacteric phase in apple (Malus ×domestica). The results [index of absorbance difference (IAD)] were correlated to quality attributes at harvest and after commercial scale storage at different conditions. Two cultivars (Red Delicious, Golden Delicious) were analyzed in two different seasons, whereas Morgenduft and Gala were analyzed only in the first and second seasons, respectively. In general, a linear reduction of the IAD values was observed in all apple cultivars along with the progression of ripening and ethylene biosynthesis. When ethylene production was inhibited by 1-methylcyclopropene (1-MCP) treatment, the decrease of IAD values was markedly reduced. IAD threshold values for each cultivar were identified, delineating the central phase of the ethylene climacteric rise. Predictive models were built by correlating IAD index to the soluble solids concentration (SSC), titratable acidity (TA), and firmness measured at harvest and after removal from different storage regimes. The best model was developed for SSC prediction on ‘Red Delicious’ apple [ratio performance deviation (RPD) = 1.88] and for firmess evaluation in ‘Golden Delicious’ apple (RPD = 1.84). Moreover, IAD values were consistently associated with the differences in fruit quality as affected by optimal and suboptimal storage conditions. The IAD, due to its acceptable accuracy and speed of assessment, can be a promising tool for assisting in sorting apples before and after storage in warehouses or commercial packing lines. IAD cannot totally replace standard ripening indices, but can effectively supplement data for these parameters.

Comparative study of the effects of black or white hail nets on the fruit quality of ‘Golden Delicious’ apples

Introduction. The use of hail nets to protect apples during development and maturation on the tree is very common in Mexico. This practice can cause changes in fruit quality and aroma composition. The effects of the hail net color on the quality and aroma volatile production of apple cultivated in Chihuahua, Mexico, were evaluated. Materials and methods. ‘Golden Delicious’ apple trees were covered with white or black hail nets. Apple samples were harvested weekly from August to early October, and analyzed for weight, axial and equatorial diameters, color (°Hue), firmness, total soluble solids (TSS), acidity, ethylene production (EC), and aroma volatile composition. The photosynthetically available radiation (PAR) was measured every ten days under each hail net and outside. Results and discussion. Apple quality was affected by hail net color. Black hail nets delayed maturation and quality development of apples by one week when compared with white hail nets. The PAR values were 18% lower under black nets than under white nets. Quality parameters at commercial harvest (162 days after full bloom) showed that white-net apples presented 7% lower firmness, 11.1% less acidity, 8.3% higher TSS and a more developed yellow color, when compared with black-net apples. In addition, white-net apples presented higher contents of the main aroma compounds (in μg L-1 ) 1-hexanol (8.09 vs. 4.38), 2-methyl-1-butanol (6.24 vs. 2.65), and 2-methyl-butyl acetate (0.47 vs. 0.16). At the same maturity stage (beginning of the climacteric rise), no difference was found between white- and black-net apples in TSS, acidity, firmness and aromatic compounds. Conclusion. Hail net functionality goes beyond protecting orchards from hail damage; hail net color affects the apple maturation rate, quality and aroma volatile production.

Molecular Cloning, Structural Characterization, and Ripening-Related Expression of Lipoxygenase Genes from Three Persimmon Cultivars Differing in Postharvest Ripening Rate

A novel lipoxygenase (LOX) gene, DkLOX4 (KF035132), and the full-length DkLOX3 (KF035131) gene were identified from persimmon fruit, and transcriptional profiles of both genes in three persimmon cultivars with different ripening rates were investigated using quantitative real-time PCR (qRT-PCR). We also studied their expression in response to propylene and 1-methylcyclopropene (1-MCP), which can promote or impede fruit ripening. Phylogenetic analysis indicated that both DkLOX3 and DkLOX4 belong to the 9-LOX family. The identity of these DkLOX genes was confirmed by functional expression in bacteria. The results showed that both DkLOX3 and DkLOX4 possessed the expected LOX activity. qRT-PCR analysis showed that all DkLOX genes were expressed abundantly in persimmon fruit during ripening, but distinctly different expression patterns were evident. Expression patterns of all DkLOXs generally paralleled the climacteric rise and maxima in ethylene production. The trajectories of transcript accumulation and the expression peaks also paralleled the declines in fruit firmness and increase in LOX activity and malondialdehyde (MDA) content. The expression level of DkLOX3 was significantly higher than that of the other two DkLOXs, its expression maxima followed the order from high to low and early to late in ‘Fupingjianshi’, ‘Huoshi’ and ‘Ganmaokui’. And expression of DkLOX3 was particularly up-regulated by propylene treatment, and down-regulated by 1-MCP treatment. Overall, the results reported here indicate that LOX genes, especially DkLOX3, may play an important role in persimmon fruit ripening.

HIGHER SALT TOLERANCE OF PHYSALIS PERUVIANA L. CALLUS WITH REDUCED PEROXIDASE ACTIVITY COMPARED TO ITS IN VITRO RAISED SEEDLINGS

The present study was conducted to evaluate the effect of N aCl on the comparative growth and biochemical parameters of seedlings and callus of Physalis peruviana . T he growth of seeds of P. peruviana was studied on MS (control) , MS+50, 100 and 150 m M NaCl , respectively . The seeds germinate d on all treatments but se edlings survived up to radic l e emergence only , on MS supplemented with 100 mM and 150 mM NaCl . The c allus induced on MS medium supplemented with B AP (0.2 mgL - 1 ) and NAA (1.0 mgL - 1 ) using s tem explants from the se see dlings ( control ) was sub cultured on sa lt supplemented MS medium . T he callus grew well up to 100 mM NaCl, where as the seedlings failed to grow . Biochemical analysis indicated that in vivo the seedlings combat with the salt stress by accumulating more phenolics (especially in shoot) and undergoing higher peroxidase activity as compared to control . 100 mM NaCl raised c allus ( in vitro ) has been found to be more tolerant to salt stress as comp ared to similarly treated seedling s, accumulating protein and proline rather than phenolics and peroxidases , i ndicating the mechanism of tolerance in vitro to be primarily through osmotic balance and generation of reductant (phenolics) diminishing the generation of free radicals vis - a - vis climacteric rise of peroxidase activity .