Maintenance of fresh boysenberry fruit quality with UV-C light and heat treatments combined with low storage temperature

Summary

Mature boysenberries (Rubus hybrid) were harvested, heat-treated (45°C for 1 or 3 h or 47°C for 1 h) or exposed to UV-C light (2.3, 4.6 or 9.2 kJ m^–2), and stored at 20°C for 2 d. Fruit treated with 9.2 kJ m^–2 or 45°C for 1 h showed less damaged drupelets per fruit and/or remained firmer than untreated fruit after 2 d. Those treatments were selected for further analyses. In another experiment, boysenberries were either UV-C (9.2 kJ m^–2) or heat-treated (45°C for 1 h) and stored either at 20°C for 1 d or at 0°C for 4 d before transfer to 20°C for 1 d. Both UV-C and heat treatments reduced softening and/or fruit damage. Treated fruit had lower respiration rates and anthocyanin leakage than control fruit suggesting greater tissue integrity. Titratable acidity, pH, total sugar content and antioxidant activity in treated fruit showed fewer changes than in control fruit when stored at 20°C for 1 d. Results suggest that heat or UV-C treatment, alone or in combination with refrigerated storage, may be a useful non-chemical mean of maintaining boysenberry fruit quality and extending postharvest life.     

细胞分裂素类生长调节剂对青花菜采后衰老的影响

 以青花菜‘绿皇后’品种为试材, 研究了25 ℃条件下细胞分裂素类生长调节剂KT、6-BA和 CPPU对延缓青花菜采后衰老的效果。结果表明: 3种细胞分裂素类生长调节剂处理均在不同程度上延缓了青花菜花蕾黄化和叶绿素分解, 推迟了呼吸和乙烯跃变峰出现的时间, 降低了峰值, 并维持了细胞膜稳定性。内源激素测定结果表明, 6-BA和CPPU处理使青花菜花蕾在试验的前期阶段(12～84 h) 一直保持相对较高的内源IAA和GA水平, 相对较低的内源ABA水平。3种细胞分裂素类生长调节剂以CPPU延缓青花菜衰老效果最为明显, 其次是6-BA, KT效果最弱。延缓青花菜采后衰老效果随着处理的浓度增加而增加, 以40 mg·L^-1 CPPU延缓青花菜衰老效果最佳。     

Cover Crops For Fruit Plantations: V. Effect of Form and Time of Application of Nitrogen on Orchard Swards

Summary

The effects of storage temperature on quality and physiological responses in Chinese bayberry fruit (Myrica rubra Sieb. and Zucc. cv. Wumei) were investigated. Freshly harvested bayberries were stored at 20°C, 10°C, or 1°C for 60 h, 5 d, or 14 d, respectively. The rates of respiration and ethylene production, fruit firmness, total sugars, organic acids, and total soluble solids (TSS) contents, total titratable acidity (TA), pH, relative electrical conductivity (REC), and polyphenol oxidase (PPO) activity of fruit were measured during storage. The results showed that the rates of respiration and ethylene production decreased during storage, and that their values were lowered significantly by decreasing the storage temperature. Low temperatures maintained higher TSS contents, TA, and fruit firmness and inhibited any increases in pH, REC, and PPO activity in bayberry fruit. There was a significant decline in citric acid and sucrose contents during storage, with a more rapid decrease occurring at higher temperatures. The data obtained indicate that cold storage is an effective way to maintain quality and chemical components in Chinese bayberry fruit.     

Postharvest heat treatment as a possible means of reducing superficial scald of apples

A pre-storage heat treatment of 38°C for four days applied to apples (Malus domestica cv. ‘Granny Smith’) before standard storage in air at 0°C was found to inhibit the development of superficial scald. Apples stored for three months after heat treatment had superficial scald levels similar to those of apples dipped in diphenylamine (DPA), while all control apples had scald. This inhibitory effect was no longer apparent after five months of storage. The heat treatment inhibited the accumulation of α-farnesene and conjugated trienes in apple cuticle while DPA inhibited only a-farnesene oxidation. Heat treated apples also had lower polyphenoloxidase activity in the peel than untreated apples. This treatment may be a substitute for chemical treatments for short-term storage of scald- susceptible apple varieties.     

Phenotype analysis of mycelium growth regeneration after heat stress in a Lentinula edodes F2 population

Heat stress is one of the major abiotic stresses that adversely affect growth and yield in Lentinula edodes (Shiitake mushroom) under natural cultivation. In this study, two parental strains (L808 and Lsm9), an F₁ strain, and an F₂ population derived from their hybrid progeny were used to evaluate the regeneration of mycelia after heat stress. A multi-level heat stress experiment showed that the dynamics of radial mycelium expansion of the two parents followed a linear equation after heat stress treatment at 37°C for 4–24 h, 42°C for 4–16 h, or 45°C for 4 h. Three indices were selected to describe the regeneration ability of the strains, including the number of regeneration days (NRD), the real growth rate after heat stress (V_regeneration), and the regenerative index (RI). L808 presented a faster rate of regeneration, while Lsm9 had better regeneration quality. The phenotype analysis of the F₂ population showed that these indices were controlled by multiple genetic factors with high heritability. Four strains were selected from the population, pyramiding the advantages of heat resistance from the two parents. The results will help our understanding of the genetic features of this mushroom after extreme high-temperature stress.     

The effect of conditions of storage on the respiration of apples. VI. The effects of temperature and controlled atmosphere storage on the relationship between rates of production of ethylene and carbon dioxide

Studies on freshly harvested fruit of three apple cultivars kept in air or under C.A. conditions at 12°, 7.2°, 3.3° and 0 °C have shown that the initiation of ethylene production is not necessarily associated with the onset of the respiration climacteric, and therefore cast doubt on the belief that ethylene is a ripening hormone. The dissociation of the two phenomena was effected by low temperatures and by storage under C.A. conditions.

The studies showed also that there is a linear relationship between rate of production of ethylene and its concentration in the intercellular spaces of the fruit.     

The morphological development of cauliflower and broccoli cultivars depending on temperature

In growth chambers the effect of temperature (12–27°C) on the growth and development of cauliflower cultivars of temperate and tropical climates, as well as of broccoli cultivars, was tested. No difference was found between the cultivars as regards dry matter production and curd growth, but a difference was found in the time of curd initiation. The early cauliflower ‘Aristokrat’ does not form lateral shoots or floral buds before elongation of the inflorescence at any temperature level. This always occurs in broccoli cultivars. The tropical cauliflowers have an intermediate position. At low temperatures (12–17°C) only 12–14 leaves are formed. Many lateral shoots are initiated and a broccoli-like curd with fertile flowers is developed. At high temperatures (22–27°C) the same cultivars produce a considerably higher leaf weight, less lateral shoots are initiated, and a cauliflower-like curd without floral buds is formed.     

The effects of heat treatment on hardseededness of serially harvested okra seed lots at optimum and low temperatures

A heat treatment of 50°C for 2 days increased both germination rate and capacity of serially harvested (36, 39, 43, 46, 50, 58 DAA) okra (Abelmoschus esculentus (L.) Moench cultivar Akköy) seeds. The more mature the seeds the better the response to treatment. Maximum advantage was obtained from seeds harvested 58 DAA, at which maximum hardseededness occurred and at an incubation temperature of 18°C as opposed to 25°C. Treated seeds of 58 DAA showed germination of 84 and 48% at 18 and 25°C, respectively. Eradication of hardseededness by the treatment was associated with an increased imbibition rate and electrical conductivity of steep water. The better results at 18°C indicate that the heat treatment can be used by commercial companies and individual producers for early sowings in order to obtain better seedling establishment.     

Seed germination of seven pepper cultivars at constant or alternating high temperatures

Summary

Seeds of seven pepper (Capsicum annuum L.) cultivars (Anaheim TMR 23, California Wonder 300, Coronado, Jalapeno M, Ma Belle, Mercury, and Yolo Wonder B) were germinated at constant day and night temperatures of 25,30,35 and 40°C or at alternating temperatures of 40/25,40/30 and 40/35°C for 14 days. Germination percentages and rates were similar at 25 and 30°C. Largest differences in cultivar responses occurred at 35°C where germination percentages ranged from 24 to 96%, and rates, calculated as summation of the number of seeds germinated on a given day divided by day number, varied from 3 to 26 (theoretical maximum value of 100). At 40°C, germination percentages were less than 5% and rates were less than one for all cultivars. Cultivars with the most heat tolerance were ‘Mercury’ and ‘Yolo Wonder B’. At alternating temperatures, germination percentages and rates were higher than those at constant 40°C. The increases were greatest when the temperature was lowered by 15°C (40/25°C) and least when temperatures were lowered by 5°C (40/35°C). Tetrazolium tests showed that a large percentage of the ungerminated seed was still viable from the highest temperature. At lower temperatures, fewer ungerminated seeds were viable with no viable ungerminated seeds from the lowest temperature.     

Some physiological changes in strawberry (Fragaria × ananassa ‘Camarosa’) plants under heat stress

Summary

The effects of heat injury induced by long exposures were evaluated in strawberry (Fragaria × ananassa ‘plants’) Camarosa in this study. Seedlings were grown in 14 × 12 cm pots using perlite for three weeks at 25/10°C day/night temperature, and watered daily by modified 1/3 Hoagland nutrient solution. Half of the plants were transferred to a growth chamber with a constant 25°C, 16/8 h (light/dark) photoperiod regime and 1200 lux light intensity for a week to acclimate the plants. Temperature was increased stepwise (5 K per 48 h) to 30, 35, 40°C and finally to 45°C. In addition to others, plants were transferred from the outside to the growth chamber, at each temperature step to impose a heat shock. Leaf relative water content (RWC, %), loss of turgidity, chlorophyll content (Spad value) and heat-stress tolerance (HTS; LT₅₀) were measured in control and stressed plants. Total soluble proteins and total DNA were extracted from the leaves following the above treatments using standard procedures and total protein contents were determined using a Bradford assay. In general, effects of gradual heat stress (GHS) and shock heat stress (SHS) on the variables studied were mostly significant, except for chlorophyll content, while the effect of temperatures was significant for all the variables. Interaction between the heat stress type and temperature treatments was not significant for leaf RWC, loss of turgidity and chlorophyll content. Data also indicated that total protein and DNA contents were changed significantly by heat stress types (GHS and SHS) and/or temperature treatments. The plants exposed to GHS exhibited a significant increase in HST compared with the plants exposed to SHS (LT₅₀ of 41.5°C and 39°C, respectively). Consequently, gradual heat stress increased HST in strawberry leaves. Increased HST may be associated with the accumulation of several heat-stable proteins in GHS plants.     

Induction of sunscald damage in tomatoes under natural and controlled conditions

Typical sunscald injury was induced in mature-green tomato fruit under controlled conditions. During the initial phase, the induction period, exposure to temperatures of 40°C or higher was necessary. Symptoms of sunscald became visible during the subsequent incubation period at room temperature. A relatively short induction period at high temperatures, e.g. 18 h at 45.1°C, was equivalent to more prolonged induction at more moderate temperatures, e.g. 28 h at 40.8°C.In addition to heat, visible light was necessary for the development of typical sunscald symptoms. The light treatment was most effective when applied both during the induction and the subsequent incubation period, resulting in 100% of fruit with sunscald. When illumination was restricted to the induction period, 13% of the fruit escaped injury, as compared to 66% of healthy fruits when light was applied during incubation only. It was concluded that sunscald is caused by the concurrent action of two external factors, heat and light, suggesting a mechanism of diversion of energy from the photosynthetic pathway into abnormal photodynamic reactions.     

Amount of Cortical and Epidermal Tissue Shed From Roots of Apple

Rates of CO₂ production by cv Idared apples were progressively reduced by lowering O₂ levels from 21% to 2% and 1%. Although lowering the temperature from 4° to 2°C also reduced the respiration rate, fruits stored in 1% and 2% O₂ were respiring faster after 100 days at 0°C than at 2° or 4°C. After 192 days the air-stored fruit also showed an increase in respiration rate at 0°C. These higher respiration rates preceded the development of low temperature breakdown in fruit stored in air, 2% and 1% O₂ at 0°C and in 1% 0₂ at 2°C. Progressively lower O₂ concentrations reduced ethylene production whilst increasing the retention of acid (expressed as malic), soluble solids, chlorophyll and firmness. In the absence of low temperature breakdown the effects of reduced temperature on fruit ripening were similar to those of lowered O₂ concentrations. The quality of apples stored at 4°C in 1% O₂ was markedly better than in 2%; the fruits were also free of core flush (brown core) and other physiological disorders.     

1—甲基环丙烯延缓青花菜衰老的效应及机理

 研究了1—甲基环丙烯(1-MCP)对青花菜衰老的影响。结果表明，0～20 µL/L的1-MCP在20℃下处理青花菜花球6 h，能延长2O 藏条件下苛仡菜的货架寿命，延缓花蕾中营养成分叶绿素、类胡萝卜素和维生素c等的降解，其中以2.5 µL/L处 的效果最佳。进一步研究还表明2.5 µL/L 1-MCP处理抑制花蕾的呼吸速率和乙烯释放速率，行使 藏期 花蕾的蛋白质含量升高；丙二醛(MDA)含量下降，使超氧化物歧化酶(SOD)和过氧化氧酶(CAT)的活性升高，过氧化物酶(POD)的活性下降，同时，SDS-PAGE分析表明，这一处理使花球中醇溶性蛋白和水溶性蛋白的组分和含量发生明显变化     

Protective effects and mechanism of heat shock response on cardiovascular system in rats after heat exposure

AIM:To study protective effects and mechanism of heat shock response (HSR) on cardiovascular system in rats after heat exposure.METHODS:The study was divided into 2 experiments:①Protective effects of HSR on cardiovascular system in rats after heat exposure.SD rats randomly allocated into 2 groups:heat shock group (HS group), sham control group(SC group).HS group were treated with heat shock, but SC group weren't.After re-covering for 20 h at room temperature, two groups exposed to death in thermal environment, and blood pressure and elec-trocardiogram were measured continuously.Through Chart software mean arterial pressure(MAP), existent time etc were acquired.②SD male rats randomly allocated into 3 groups:HS group, SC group and normal temperature control group(NC group).NC group weren't treated.The treatment in HS and SC group was identical with in the first experiment, but it would be terminated at 73 min after heat exposure, meanwhile content of MDA of myocardium were measured.RESULTS:① Existent time in HS group was longer than that in SC group and shock arrived later; ② During earlier period after heat exposure MAP had no significant changes between HS and SC group, but after 60 mins MAP in HS group were higher than that in SC group; ③ Compared with NC group, content of MDA in myocardium in SC group was higher significantly at 73 min after heat exposure. Howerer, content of MDA in HS group was lower than in SC group, and had no significant changes with NC group.CONCLUSION:Through decreasing production of MDA in myocardium, HSR has a protective effect on cardiovascular system in rats after heat exposure.     

Effect of storage temperature on ripening and quality of custard apple (Annona squamosa L.) fruits

Summary

The effect of storage temperature on ripening, shelf life and chemical composition of custard apple (Annona squamosa L.) fruits stored at 10,15,20 and 25°C was studied. The safe range of storage temperature was found to be between 15 and 20°C, with maximum shelf life at 15°C. The ripening of fruits was observed on days 4, 6 and 9 of storage at 25,20, and 15°C respectively. The colour of the pulp, texture, taste and flavour of ripe fruits held at 25 and 20°C were superior followed by fruits stored at 15°C. At 10°C, the fruits became hard with surface blackening, messy pulp and less sweetness. The major changes during ripening were a continuous decrease in fruit firmness and starch content and a continuous increase in TSS and sugars, the changes being more rapid at 25 and 20°C than at 15 and 10°C. The acidity and ascorbic acid contents increased slightly during the initial stages of ripening followed by a decline, in the fruits stored at different temperatures. Custard apple fruits stored at 25 and 20^CC had a clear climacteric peak whereas those stored at 15 and 10°C did not show any distinct rise in respiration rate. Ethylene peak (2.40 µl kg^–1 h^–1) coincided with the respiratory climacteric at 25^CC storage, corresponding with the peaks in TSS, sugars, ascorbic acid and acidity.     

Temperature requirements for the germination of olive seeds (Olea europaea L.)

Summary

Olive seeds cv Chondrolia Chalkidikis were subjected to temperatures of 5°, 10°, 15°, 20°, 25° and 30°C for one, two or three months, and were then transferred to 20°C. Exposure to 10° and 15° for one month or more caused higher emergence percentages compared to that at a constant 20°C. The highest germination rate was observed when seeds subjected to 10°C for one month were then transferred to 20°C. Seeds at 5°, 25° and 30°C did not germinate while being held to these temperatures; even when transferred to 20°C the percentage and rate of emergence were lower than those of seeds held at constant 20°C. In another experiment, in which seeds were subjected to 10°C for 0, 2, 4, 6 and 8 weeks before being transferred to 20°C, it was found that four weeks exposure to 10°C was near optimal. Emergence percentages of seeds at constant 10°C or at diurnally alternating temperatures of 10° for 16 h/20° for 8 h were high and equal (92%), but emergence in the latter treatment was slower. Alternating 10° with 25°C resulted in a 95% reduction of the emergence percentage. Transferring seeds immediately after chilling at 10°C for three or four weeks to 25°C, partially reversed the effect of the low temperature. However, the chilling effect could not be reversed when the seeds were subjected to 10°C for five weeks.     

The susceptibility of pepper (Capsicum annuum) to heat induced flower abscission: Possible involvement of ethylene

SUMMARY

Heat stress causes abscission of flowers in pepper plants and thus reduces yield. In the present study, we investigated the involvement of ethylene in heat-stress related flower abscission, by comparing the response of flowers of bell pepper, cv. Maor, known to be sensitive to flower abscission, and flowers of paprika, cv. Lehava, a resistant cultivar of Capsicum annuum. Their differing susceptibilities to high temperatures depend on light. Under high-temperature, high-light conditions, bell pepper was less susceptible than paprika, but, under high-temperature low-light, bell pepper was more susceptible. At high temperatures, flower explant abscission was much higher with bell pepper than paprika. Ethylene production (EP) by bell pepper explants reached a maximum at 34°C and decreased at higher temperatures (42 and 48 C), while in paprika EP rates were lower and reached the maximum at 42°C. Explants of bell pepper flowers were more susceptible to exogenous ethephon than paprika flowers. The sensitivity of a collection of pepper cul-tivars to heat induced flower abscission was more closely correlated with their flower sensitivity to ethephon than with the flower EP rate. We suggest that the differential susceptibility of bell pepper and paprika to heat stress is a result of both different ethylene production by their flowers and their differing sensitivities to ethylene produced under high-temperature stress. However, the sensitivity of the flower to ethylene may be more important in inducing their abscission.     

The influence of temperature on photosynthesis of different tomato genotypes

Net photosynthesis and dark respiration from whole plants of various tomato genotypes were measured in a closed system. At low irradiance (27 W m^?2) and low external CO₂ concentration (550 mg m^?3), net photosynthesis of 10 genotypes was found to vary between 0.122 and 0.209 mg CO₂ m^?2 s^?1. Correlation was observed between net photosynthesis, net uptake on a daily basis (8 h photoperiod at 20°C and 16 h nyctoperiod at 10°C), specific leaf weight and leaf area ratio. At high irradiance (243 W m^?2), high external CO₂ concentration (1480 mg m^?3) and ambient temperatures of 10, 18, 20 and 26°C, four genotypes were analysed. ‘F6 I.V.T.’ had the highest rate of photosynthesis at 10°C, while ‘Sonatine’ ranked high at 26°C. Dark respiration increased with temperature, except in the case of ‘Bonabel’ where the effect of temperature was slight.     

Effects of post-harvest storage conditions on the levels of glucosinolates in broccoli sprouts (Brassica oleracea var. italica) grown under different temperature regimes

Summary

Broccoli sprouts have been recognised as a rich source of glucosinolates, particularly 4-methylsulphinylbutyl glucosinolate, the precursor of the potent anti-cancer compound, sulphoraphane. Previous results have shown that temperature can significantly affect the levels of glucosinolates. In this study, we showed how sprout age and storage temperature affected glucosinolate levels in broccoli sprouts grown under different temperature regimes. Experiments were conducted in growth cabinets with day/night temperature regimes of 30°/15°C, 22°/15°C and 18°/12°C. At 9, 10 and 11 d after sowing in the first temperature regime, 10, 11 and 12 d in the second, and 12, 13 and 14 in the third, sprouts were submitted to 4°C or 20°C to simulate refrigerated and room temperature storage. Sampling was done after 1 d or 2 d of exposure to these conditions. The results showed that total glucosinolate levels and the potential health effects of broccoli sprouts depended on the growth temperature regime (P < 0.05), the age of the sprouts (P < 0.001), and the storage conditions (P < 0.01). The highest total glucosinolate levels (65.7 µmoles g^–1 dry weight) were obtained under the 30º/15°C temperature regime for the youngest sprouts (harvested 9 d after emergence), after being submitted to a storage temperature of 4°C for 24 h. However, these levels were much lower than in 3-d-old sprouts. Consuming old sprouts provides less health-protective effects due to reduced levels of glucosinolates.