Can someone explain?

[Raymondo]

If, as Chuck Marr stated above (see sic_transit_gloria's post), the xylem flow system remains open, there's no need for osmosis. Water can move in but not out because it moves out via the phloem system, which is blocked, hence the splitting.

[TZ-OH6]

Yes, the xylem are just open tubes, but without the cell membranes in the fruit for the osmotic force to build against/behind there would be no water movement, pressure, cell swelling, splitting. And in the roots water must pass through at least one cell layer (endodermis) to enter the vascular cylinder.


The abscision layer simply stops sugar movement from the leaves to the fruit, so the fruit have to ripen with stored starch reserves from early growth. Mineral nutrients from the soil (N,P,K, Ca, Mg, etc) come in with the xylem root water. So sugar content is dependent on the amount of sun the plant gets when the fruits are little/developing, not while they are ripening, but fertilizing during ripening "could" affect flavor as well. That being said, I would expect the absolute temp and day night temp change to affect the flavors in a garden ripened fruit compared to a stable room temp ripened fruit because not all chemical reactions (e.g. fruit cell wall softening vs. starch to sugar conversion) proceed at the same rate. Taste tests are needed, but you can't take an early season slow ripened counter-top tomato and compare it to a fast ripened vine tomato because the conditions (sun, temp etc) on the little green fruits might have been different. They would both have to be mid season grown fruits.

[feldon30]

Excellent thread!!

I knew there was a reason why picking early is a good idea.

[where_with_all]

wow- i just learned something. its threads like this that keep me comming back! I am going to try a test

[kdoble]

I love that I just got educated with cold hard facts on the biological functioning in these plants. It's so rewarding to learn something so valuable. I was completely convinced that letting the tomato ripen fully on the vine was essential for full flavor.
Thanks so much for priceless info!

[Hilde]

I learned something new too. It looks like I have to start picking earlier.

Hilde

[tomatoguy]

Xylem up and Phloem down. A great mnemonic device along with sohcahtoa, Roy G. Biv and Eli the Iceman.

mater

[BigdaddyJ]

I pick every second or third day usually and I always try and pick before heavy rains are due. When I'm out there picking, I pick! I will pick anything close to ripe. They ripen just fine indoors and I haven't noticed a taste difference between right off the vine or one that sat for three days on a table before total ripe.

Thanx for all of your contributions on this message.

[dcarch]

Just when you think that I am done with my dumb questions -----------------

This barrier that supposely cuts the fruit off from the plant, I would assume that it does not act like an electric switch. It doesn't go on in an instant like flipping a switch.

So, at which point it is 25%, 50%, 75%, 100% effective?

When the fruit is still green? 25% pink? 75% pink?

So, when should you pick?

Sorry again.

dcarch

[dice]

So, at which point it is 25%, 50%, 75%, 100% effective?

Rate and timing of development of the abcission layer relative
to fruit ripeness may vary with cultivar, too (besides nutrient
supply, weather, etc). When it happens for a not pollenated
flower where the cells in the stigma and/or ovary have died,
it seems to happen pretty fast, a couple of days at most.

[Eric02476]

Fascinating thread. My #1 pest problem is squirrels, and sadly, my suburban town isn't too keen on firearms discharge within municipal limits, if you know what I mean. The critters almost always wait until the fruit is well ripened -- obviously never having learned the joys of fried green tomatoes -- so I am going to try this. Thanks for the great discussion.

Eric

[Ruth_10]

Originally Posted by TZ-OH6

Yes, the xylem are just open tubes, but without the cell membranes in the fruit for the osmotic force to build against/behind there would be no water movement, pressure, cell swelling, splitting. And in the roots water must pass through at least one cell layer (endodermis) to enter the vascular cylinder.


The abscision layer simply stops sugar movement from the leaves to the fruit, so the fruit have to ripen with stored starch reserves from early growth. Mineral nutrients from the soil (N,P,K, Ca, Mg, etc) come in with the xylem root water. So sugar content is dependent on the amount of sun the plant gets when the fruits are little/developing, not while they are ripening, but fertilizing during ripening "could" affect flavor as well. That being said, I would expect the absolute temp and day night temp change to affect the flavors in a garden ripened fruit compared to a stable room temp ripened fruit because not all chemical reactions (e.g. fruit cell wall softening vs. starch to sugar conversion) proceed at the same rate. Taste tests are needed, but you can't take an early season slow ripened counter-top tomato and compare it to a fast ripened vine tomato because the conditions (sun, temp etc) on the little green fruits might have been different. They would both have to be mid season grown fruits.

I think this is closest to reality, if such a thing exists when judging tomato flavor. The problem I have with the Marr article is its oversimplification (and the usual extension service slant towards commercial growers). The fruit is not "just hanging there" completely cut off from the rest of the plant. The abscission layer process begins with cell lengthening and is not instantaneous.

I have a copy (pdf file) of a recent article that I will send to those interested if they PM me.

H. Gautier et al."How Does Tomato Quality (Sugar, Acid, and Nutritional Quality) Vary with Ripening Stage, Temperature, and Irradiance?" J. Agric. Food Chem. 2008, 56, 1241-1250.