Ripening on the vine

gorbelly · September 11, 2015

I've actually been doing a lot of research on tomato fruit abscission recently. It seems it's not true that tomatoes no longer receive anything from the plant once it blushes. There's no "membrane" that seals off the fruit as one reads commonly around the internet. An abscission zone forms as the fruit develops and matures, but all that means is that the plant is preparing a point at which cells can grow or shrink on one side of the zone more quickly than on the other side so that the leaf, flower, or fruit can break off at that point. The xylem (carries mostly just water) atrophies in the pedicel throughout the tomato maturation process, but the phloem (carries nutrients, etc.) increases in cross sectional diameter, and phloem can continue to carry both water and nutrients into the fruit until you pick it.

My guess is that larger tomatoes have enough mass accumulated in "active materials" inside the fruit that depriving the fruit of the final few days of whatever's coming up in the phloem has no detectable effect on the end result for the average person. But cherry tomatoes could be small enough that the average person may be able to taste the difference between cherries ripened on the vine vs. off the vine.

At least, that's my understanding up to this point. The understanding of this isn't settled, though--I don't think science has a definitive answer to how much interaction there is between the fruit and the plant later in ripening, but we do know that the pedicel and the abscission zone remain green and juicy even when we wait to pick a tomato until it's perfectly ripe. And since we know that tomatoes can crack even late in ripening if there's a heavy rain, we know that water is being transported into the fruit until the very end, and since we also know that that water is getting there via the phloem, which transports nutrients and other dry matter, there's clearly still something besides just water being transported to the fruit at that point even late in ripening.

September 11, 2015	#16
gorbelly Tomatovillian™ Join Date: Jul 2015 Location: Southeastern Pennsylvania Posts: 1,069	I've actually been doing a lot of research on tomato fruit abscission recently. It seems it's not true that tomatoes no longer receive anything from the plant once it blushes. There's no "membrane" that seals off the fruit as one reads commonly around the internet. An abscission zone forms as the fruit develops and matures, but all that means is that the plant is preparing a point at which cells can grow or shrink on one side of the zone more quickly than on the other side so that the leaf, flower, or fruit can break off at that point. The xylem (carries mostly just water) atrophies in the pedicel throughout the tomato maturation process, but the phloem (carries nutrients, etc.) increases in cross sectional diameter, and phloem can continue to carry both water and nutrients into the fruit until you pick it. My guess is that larger tomatoes have enough mass accumulated in "active materials" inside the fruit that depriving the fruit of the final few days of whatever's coming up in the phloem has no detectable effect on the end result for the average person. But cherry tomatoes could be small enough that the average person may be able to taste the difference between cherries ripened on the vine vs. off the vine. At least, that's my understanding up to this point. The understanding of this isn't settled, though--I don't think science has a definitive answer to how much interaction there is between the fruit and the plant later in ripening, but we do know that the pedicel and the abscission zone remain green and juicy even when we wait to pick a tomato until it's perfectly ripe. And since we know that tomatoes can crack even late in ripening if there's a heavy rain, we know that water is being transported into the fruit until the very end, and since we also know that that water is getting there via the phloem, which transports nutrients and other dry matter, there's clearly still something besides just water being transported to the fruit at that point even late in ripening.