R. B. H. Wills

Evidence for the function of the free radical gas - nitric oxide (NO°)-as an endogenous maturation and senescence regulating factor in higher plants

Abstract The hypothesis that endogenously-produced nitric oxide (NO • ) gas is a natural plant growth regulator was experimentally tested. Experimentation encompassed a wide spectrum of both climacteric and non-climacteric varieties of fruits, flowers, vegetables and legume sprout species. Specific NO • probe monitoring of both vegetative and generative plant organs revealed that temporal progress of maturation and senescence goes hand in hand with a significant decrease of NO • emission. Conversely, exogenous application of the gas either by direct fumigation in an O 2 -free atmosphere or by means of NO • releasing biochemicals such as N- tert -butyl-α-phenylnitrone and 3 morpholinosyl-nonimine, markedly delayed senescence and maturation. NO • decrease was moreover stoichiometrically related to ethylene upsurge, this phenomenon also being geared to ethylene increment under short-term heat stress. Furthermore, a classic foliage expansion bioassay indicated a concentration-dependent growth effect evidenced as a typical growth regulator-like response where low concentrations promote, and high concentrations inhibit growth. Regarded together, experimental data lends support to the possible role of NO • as a natural senescence-delaying plant growth regulating agent acting primarily, but not solely, by down regulating ethylene emission.

Postharvest: an introduction to the physiology and handling of fruit and vegetables

Structure and composition of fruit and vegetables physiology and biochemistry of fruit and vegetables effects of temperature effects of water loss and humidity storage atmosphere physiological disorders quality evaluation of fruit and vegetables pathology commodity treatments handling, packaging and distribution technology of storage.

Effect of 1-methylcyclopropene on the storage life of broccoli

Abstract Broccoli (Brassica oleracea, cv. Green Belt) florets were treated with 1-methylcyclopropene (MCP) at concentrations of 0.02–50 μl l−1 for 1–6 h at 20°C followed by storage at 20 or 5°C in air containing 0.1 μl l−1 ethylene and treatment at 5°C followed by storage at 5°C. MCP markedly extended the storage life through a delay in the onset of yellowing at 20 and 5°C and in development of rotting at 5°C. The beneficial effects at both temperatures were dependent upon concentration and treatment time. For broccoli treated and stored at 20°C, maximum extension in storage life of >100% was achieved with exposure to 1 μl l−1 MCP for 6 h while a 50% increase in storage life was obtained with treatment for 1 h. For storage at 5°C, treatment at 20°C was more effective in extending storage life than treatment at 5°C; treatment with 1 μl l−1 MCP for 6 h at 20°C resulted in 250% extension in storage life compared to 200% when treated at 5°C. These effects of MCP are likely to be of considerable commercial significance.

FUMIGATION WITH NITRIC OXIDE TO EXTEND THE POSTHARVEST LIFE OF STRAWBERRIES

Abstract Strawberry (Fragaria ananassa Duch. cv. Pajaro) fruit were fumigated with nitric oxide immediately after harvest. Fumigation was performed in an anaerobic nitrogen atmosphere for up to 2 h at 20°C at nitric oxide concentrations from 1.0 to 4000 μl l−1 then held at 20 and 5°C in air containing 0.1 μl l−1 ethylene, a concentration prevalent in ambient air at fruit and vegetable markets. Treatment at both temperatures extended the postharvest life of strawberries, the most pronounced effect being obtained with nitric oxide in the concentration range 5–10 μl l−1 which produced >50% extension in shelf life. The possibility of commercial application is discussed.

Herbal products: active constituents, modes of action and quality control.

An overview is given of the current position of medicinal herbs in general in relation to usage, market and production, types of pharmacological activity and how they differ from conventional drugs. The increasing importance of quality and manufactured products is also discussed. A more detailed consideration of these issues is given in relation to echinacea, valerian and St Johns wort as these herbs are well studied, are market leaders and have widespread community usage.

Harnessing Senescence Delaying Gases Nitric Oxide and Nitrous Oxide: A Novel Approach to Postharvest Control of Fresh Horticultural Produce

The effects of ethylene on postharvest horticultural produce are a major limiting factor in their orderly and efficient marketing. Nitric oxide and nitrous oxide have recently been shown to inhibit ethylene action and synthesis in higher plants and their potential for commercial use to extend the storage and marketing life of fruits, vegetables and flowers is reviewed.

Effect of ethylene on postharvest life of strawberries

Abstract Strawberries are non-climacteric fruit and therefore regarded as independent of ethylene for ripening. The concentration of ethylene in punnets of strawberries in wholesale markets was found to be in the range 0.03–0.36 μl l−1 per punnet. Experiments at 20 and 0 °C, where the ethylene concentration was controlled, showed that the storage life of strawberries was extended by reducing the ethylene level. Maximum storage was obtained at the lowest ethylene levels used of 0.05 μl l−1 at 20 °C and 0.005 μl l−1 at 0 °C. The addition of potassium permanganate to punnets held at either of the above temperatures significantly extended storage life of the fruit and this may be capable of commercial exploitation.

Enzymes associated with blackheart development in pineapple fruit

The involvement of browning enzymes, polyphenoloxidase (PPO), peroxidase (POD) and phenylalanine ammonia-lyase (PAL) in blackheart development was investigated in pineapple fruit (Ananas comosus, Smooth Cayenne) following low temperature storage. An increase in PPO activity was related to the incidence of blackheart symptoms, both temporally and spatially. Fruit maturity significantly affected blackheart susceptibility; immature and over-mature fruits developed less blackheart injury than in ature fruit. The effect of maturity on blackheart susceptibility was highly correlated to the response of PPO activity to chilling. POD showed no significant change after chilling. Enhanced PAL activity was observed during chilling at 6, 13 and 18 degreesC. Chilling (6, 13 and 18 degreesC) also inhibited the increase of ascorbate peroxidase activity observed in the fruit stored continuously at 25 degreesC, but had less effect on catalase activity. The results indicate that the development of blackheart symptoms in pineapple fruit results from the disturbance of a number of metabolic processes that occur at sub-ambient temperatures

Ripening of climacteric fruits initiated at low ethylene levels

Mature, unripe mango, peach, custard apple, kiwifruit and tomato were stored at 20˚C in air containing ethylene at custard apple and mango > tomato, avocado and peach. Since the ethylene level around horticultural produce during marketing is always >0.005 L/L, the time climacteric fruit can be held in an unripe condition is currently less than optimal but intervention to limit ethylene action would appear to be only warranted for the most sensitive fruits.

Ethylene levels associated with fruit and vegetables during marketing

Over 700 measures of the level of ethylene in the atmosphere of fruit and vegetable holding areas in wholesale markets, distribution centres, supermarket retail stores and domestic refrigerators were taken over a 3-year period. The lowest ethylene levels were found in supermarket stores with a mean level of 0.017–0.035 L/L in produce receival, storage and display areas. Levels in the ambient air of wholesale markets and distribution centres were higher at about 0.06 L/L. Domestic refrigerators were grouped into those that contained or did not contain apples with the ethylene level being much higher at 0.20 L/L where apples were present and 0.029 L/L where apples were absent. Using a rating scale, which was developed from published literature on non-climacteric produce, of ≤0.015 L/L ethylene as a low level where less than 10% of potential postharvest life is lost and ≥0.1 L/L as a high level where there is higher than 30% loss of postharvest life, suggests that most produce during marketing is held in an ethylene atmosphere where 10–30% of potential postharvest life is lost.