Fruit ripening, control

Figure 5. Polygalacturonase Isoenzyme Activities and Lycopene Production During Control 1 and TA8 Fruit Ripening.

It is not yet known whether the increase of these activities in the course of fruit ripening is due to a direct synthesis of the enzymes, or whether conversion of inactive precursors into the active enzymes is involved. There is also the possibility of (a) an effect of inhibitors present in unripe fruit on the activity of endo-D-galacturonanase, and (b) disappearance of such inhibitors in the course of ripening.184 For pectinesterase, it has been speculated that plants may be able to regulate the activity of this enzyme by metabolic control of the amount and proportion of certain, naturally occurring, fatty acids.82... 

Net the crop before the fruits ripen. This will exclude birds, but squirrels and raccoons may also take the fruit. Slugs love ripening strawberries. Encourage natural predators, and put down slug traps, or use a biological control see p.97) if necessary. 

Salzman, R.A., Tikhonova, I., Bordelon, B.P., Hasegawa, P.M. and Bressan, R.A. (1998) Coordinate accumulation of antifungal proteins and hexoses constitutes a developmental controlled defence response during fruit ripening in grape, Plant Physiol., 117, 465-472. 

The second chirality source used in the synthesis of aminocyclopropane carboxylic acids was D-glyceraldehyde acetonide, which after Wittig-Homer-Emmons reaction provided the alkenes 61. Treatment with diazomethane and subsequent irradiation at low temperatures alforded the cyclopropanes 62, which were converted into several other derivatives by modification of the side chain (Scheme 11). Notably, the best results were obtained by irradiating in the presence of benzophenone as triplet sensitizer [33, 34]. Following a similar synthetic procedure allocoronamic acid 65 was prepared, which is one of the amino acids that can be processed by plant tissues and promises the possibility to control the enzymatic processes underlying plant growth and fruit ripening [35]. 

Alkenes play many important roles in biology. Ethene, for example, is a plant hormone—a compound that controls the plant s growth and other changes in its tissues. Ethene affects seed germination, flower maturation, and fruit ripening. 

How does one determine whether a particular compound is actually a plant hormone, or whether a particular process is controlled by that hormone There is no single, simple procedure. One approach is to measure the amount of the putative hormone present in the tissue and then correlate it with the amount of response. For example, the close correlation between the ethylene level in melons and the fruit ripening implicates ethylene as a controlling hormone in this process [27]. Likewise, the correlation between the amount of auxin and the rate of stem growth in a series of pea mutants indicates that auxin might regulate the rate of pea epicotyl elongation [28]. 

Ethylene is also found in plants, where it is a hormone that controls seedling growth and regulates fruit ripening. The discovery of this property led to the use of ethylene by food processors for ripening fruits and vegetables after harvest. 

Klee HJ, Giovannoni JJ (2011) Genetics and control of tomato fruit ripening and quality attributes. Annu Rev Genetic 45 41-59... 

In tomato two PSY encoding genes have been identified Psy-1 and Psy-2. Psy-1 encodes the fruit-ripening-specific isoform, which has been proved to be the key enzyme in the control of carotenoid biosynthesis [28]. Psy-2 encoded enzyme predominates in green tissues (including mature green fruit) and petals and has no role in carotenoid synthesis in ripening fruit [29, 26]. As an example of the role of this enzyme in carotenoid biosynthesis, a null mutation in Psy-1 in the yellow-flesh (r) mutant arrests carotenoid synthesis [30]. In this mutant, the accumulation of the flavonoid rutin in the fruit skin would lead to the development of yellowish fruits. 

Ethene (ethylene) - a gas whieh eontrols fruit ripening and senescence. Controls fruit and leaf drop from some trees. 

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