Old topic but wanted to share my input. I'm growing hydroponic tomatoes (various strains) at university in a lab setting (indoors under HID lights) and outdoors in a greenhouse. In one of my greenhouse NFT systems, i recently had a similar problem on 1 tomato plant (total 9 plants that share the same res and tubes). But im gonna try to diagnose your issue by mentioning what others missed out on. 1 major cause of leaf curl is compaction of root system (i.e. roots are compressed or dont have enough space to expand). This risk is exacerbated in hydroponic systems that use tubes. This was the problem i had and had to replace tubes with square tubings that have a liftable top. Once you have access to roots, you must seperate them strand by strand (i.e. so they arent sticking together). In your setup, this risk will further be exacerbated because you filled the entire pvc tube with hydroton (right?). Remove hydroton from tube and place the plant in a net cup with hydroton. Nitrogen burns usually cause browning/yellowing of leaves (similar to sun/heat burn) and not purpling. Test your solution for each chemical if possible, or use a commonly employed aggregated measuring device that shows total concentration in ppm (dont let it exceed 2500). In my system, only one plant was affected. Coincidentally, it was the largest of all plants with the most root mass. I let another normal one grow to its size to see whether it would undergo the same problem, and it did. Viral and bacterial infections that cause leaf roll usually cause it to roll up. Same with the physiological roll. If your leafs roll down AND if your stems bend, this is caused by a diminishing turgor pressure (read: not enough water reaching afflicted area). Mist several times when lights are off (no photosysnthesis) and observe increasing turgor pressure (unbending). Or, untangle roots and remove hydroton from from pipes. I tested various growing methods including fully and partially submerged roots. They all work but a submerged root cannot intake oxygen; it has to borrow oxygen from another part of the plant (i.e. a root part that isnt submerged or above ground stem). This requires energy for transportion and isnt the most efficient (optimal) way for growth and cellular processes. Lastly, an airstone in the reservoir is useless unless the reservoir is completely airtight all the way up to the plant holes. Better to keep small airstones in the pipes right under the plant roots. Those that say aerating the res prevents bacterial development.. is false. If you dont have air in res, you will get anaerobic bacteria (they grow/accumulate slowly but acidify the solution); if you have air in res, you get aerobic bacteria (not acidifying but grow extremely fast). Most bacteria prefer aerobic environments for optimum growth.

Calcium deficiency can be provoked by Magnesium excess, even when there is plenty of Ca around, you need to check out this possibility. You are using the percents on the label which makes perfect sense to a logical person, but industry enjoys exaggerating and confusing, or something like that. The N-P-K numbers are only for elements in the first case of N. P is "expressed as P2O5" and K as "K20" which inflates the phosphorus and potassium by adding some hypothetical oxygen that actually isn't in your hydroponic fertilizer. Don't ask why. No sense on reinventing the wheel, here's what Wikipedia has to say about this: The factors for converting from P2O5 and K2O values to their respective P and K elemental values are as follows: P2O5 consists of 56.4% oxygen and 43.6% elemental phosphorus. The percentage (mass fraction) of elemental phosphorus is 43.6% so elemental P = 0.436 x P2O5 K2O consists of 17% oxygen and 83% elemental potassium. The percentage (mass fraction) of elemental potassium is 83% so elemental K = 0.83 x K2O Nitrogen values represent actual nitrogen content so these numbers do not need to be converted. To convert 2.73% nitrogen to express as ppm when dissolved in water, just specify how much 2.73% fertilizer is in how much water. For 300 *grams* in 17 gallons, the ppms are estimated for the working solution by the weight of nitrogen/ weight of water. A gallon is 3785 grams. In this case 8.19g/64,345g = 0.0001273 To convert fractional part to parts per milliom (ppm) instead of percent, multiply by 1,000,000 instead of 100. That comes out to 127 ppm for N. P and K need to be adjusted by the factors mentioned to get the pure element and then calculated the same way. That's all I did. The absolute percentages in the fertilizer as you have them are not as relevant as their ratio to each other since a more concentrated fertilizer uses less weight of fertilizer to get to the same point. I do suspect that you have a nutrient problem though and my thinking base on the limited info is that there may be too much magnesium in there locking out potassium. That I got from the generalitities you've mentioned. However the symptoms as discussed sound more like nitrogen deficiency and there are no more limbs to go out on without real quantitative info and this will all make sense as you get into it more. For example, if the plants with more light are growing faster, they may have a greater nutrient demand and the plant may do what yours are doing by sapping nutrients from old growth to support and favor younger growth and reproductive tissue (tomatoes!). The last picture seems to be far more pronounced and not limited to the older growth though, not sure, the tones seem to be saturated in yellow (maybe on another monitor is shows up better but I have a cheapo monitor that freaks washing out with saturating colors) making it harder...

Britt, I agree with everything Jay said. Most of the time physiological leaf roll is merely a stress reaction, and the extreme heat is likely the cause. The last thing I'd do is repot them unless they're in small containers. Repotting would be stressful and the plants don't need more stress. Tomato plants generally do best if we leave them alone and let them grow and take care not to 'love them to death' with too much water and too much fertilizer. Having mentioned fertilizer, I'll add that it is much harder for plants to remain well-fed in this heat if they are in containers because the necessary watering leaches the fertilizers out of the soil. So if, by chance, your plants are in smalish containers that require a lot of watering, I'd take great care to ensure they are well-fed. I'd probably feed at least weekly in this heat, or maybe twice a week depending on the container size, but I'd cut the fertilizer strength in half so it is weaker to make up for the fact I was fertilizing more often. When you feed container plants with a water soluable fertilizer, their roots take up what they can and then the rest of the fertilizer often is washed out of the soil the next time you water. Shade may or may not help. If the temps are going over 105 or so, the shade doesn't help as much as you'd like because the poor plants are still so hot in the shade. If the plants are getting reflected sunlight and heat from pavement or building walls or a wooden fence, moving the containers so they are placed in a cooler area away from heat-reflecting surfaces can help. If your plants are in the ground, making sure they are well-mulched will help keep the soil cooler and that might help with the curling a little. I looked at the bare soil temperature map yesterday and it was showing a temperature of 111 degrees in my county at the time I looked at it. That is why mulching is so important--because the soil is so very hot right now and the roots are just baking in that hot soil. Honestly, though, in a summer like this, there's going to be a lot of leaf curl in the heat and that's nothing much you and the plants can do except tough it out. Sometimes leaf curl is a symptom of a disease or pest issue, but 99% of the time it is just stress. I'm so used to seeing leaf curl in hot summers that I rarely even notice the leaves are curled unless someone else notices it and mentions it to me. Then I shrug my shoulders and say something like "Oh, that's heat stress. It happens every year." Dawn

Thanks for the comments and you're welcome. I was just trying to help a little because it seemed to be such an issue this year. buck, "how long, typically, does a young plant take to grow out of leaf roll?" You aren't going to like the answer. It varies. I've had some plants get over it fairly quickly (a couple of weeks or so give or take) and some plants it took a fairly long time (I recall a Rose plant in particular that must have taken over a month). I'm sorry I can't be more specific, but I didn't take specific notes on the exact amount of time. "Oh, and one more Q, do PL's curl or roll?" I suppose they could, but I don't recall experiencing it. Right now none of my PLs do, but as you can see in the pictures RLs are doing it. And, not all RLs are doing it even though they were grown almost the exact same conditions (I didn't measure the exact amount of compost etc. in each hole). Randy