Climacteric nonclimacteric fruits

Figure 1. Effect of ethylene on respiration of climacteric and nonclimacteric fruit. Ethylene causes greatest response in climacteric fruit when applied to mature fruit prior to the climacteric rise. In nonclimacteric fruit high concentrations of ethylene stimulate respiration for short time periods. This stimulation is observed at any time upon application of ethylene (3).

Climacteric and nonclimacteric fruits respond differently to external ethylene (Fig. 18.10). Depending on the ethylene level, the respiratory increase sets in earlier in unripe climacteric fruits, but its height is not influenced. In contrast, in nonclimacteric fruits there is an increase in respiration rate at each ripening stage which is clearly dependent on ethylene concentration. 

Ethylene increases rapidly but differently in the case of climacteric fruits. The maximum values for some fruits are given in Table 18.35. However, nonclimacteric fruits produce only a little ethylene (Table 18.35). This gaseous compound increases membrane permeability and thereby probably accelerates metabolism and fruit ripening. With mango fruits, for example, it has been demonstrated that before the climacteric stage, ethylene stimulates oxidative and hydrolytic enzymes (catalase, peroxidase and amylase) and inactivates inhibitors of these enzymes. 

Several studies on irradiation of fruits and vegetables have been conducted to delay fruit ripeness, thus, their shelf life might be extended by few days to few weeks [1]. However in some horticultural crops gamma irradiation treatments initiated the climacteric ripeness sequences by inducing the preclimacteric fruits to produce stimulatory amount of ethylene [2]. Factors most likely to affect response of fruit and vegetables to irradiation may include type of fruit (climacteric or nonclimacteric), ripeness stage at expossure, dose of irradiation and post-treatment storage conditions. 

Fig. 18.10. The effect of ethylene on fruit respiration, (a) climacteric, (b) nonclimacteric. Numerals on the curves ethylene in air, ppm (according to Biale, 1994)...

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