Why do fruit get sweeter after they're taken from their stem/vine?

[wasteofo2]

Why is it that fruit continue to get sweeter after they're plucked from whatever they're growing from and sitting around? Is it that the fruit has reserves of water and Co2 built up and continues to synthesise glucose, but there is no use for it anymore?

 

[Monique]

I know for bananas starch is turned into glucose under the influence of the hormone gas ethylene that is produced by the fruit (that is why fruits ripen faster if they are lying together with bananas).

 

[iansmith]

It actually the breakdown of complex sugar such as starch and saccharose into glucose and the accumulation of glucose. The complex surgar are stored during the eearly stage of the life of the fruit. If I remember correctly fruit usually do not photosynthesise. The fruit energy is only provided by the plant. when the fruit is harvested it starts to die and try to survive on its stored sugar.

 

[wasteofo2]

Ha, so their last futile attempts at life make them all the much sweeter, that's so morbidly awesome. It's like if some creature forced humans to physically exhaust themselves and then put them in an environment without oxygen but with carbon dioxide in order to get us to build up lactic acid in our muscles as a natural flavoring right before we died.

 

[iansmith]

That futile attempts is an excellent survival mechanism. The fruit get sweater, the animals know it, eat it, then spead the seeds and the cycle is reset.

 

[hitssquad]

The sugar may also act as an antibacterial, antifungal preservative. Evolutionary pressure doesn't require that it directly benefit the survival of the fruit, though. Animals thinking it is tasty, and thereby influenced into spreading the plant seeds, may constitute sufficient evolutionary pressure by itself to continue ripening after dropping off the tree.

It should be noted, however, that not all fruits do this. Some fruits have to be left on the tree or vine or they will not continue to ripen. IIRC there have been designated three classes of ripeners, according to how self-sufficient the ripening characteristic is.

Interestingly, kiwifruit will not ripen on the vine but will slowly ripen in a refrigerator.