IRA FLATOW, host:
This is Talk of the Nation Science Friday. I'm Ira Flatow. A little bit later in the hour, we'll take a look inside your brain. Hope there is something in there. But first, maybe you are thinking ahead to those warm summer months. I'm thinking about getting some tomato plants in the ground, you know, so that you can enjoy it a ripe, red, heirloom tomato later on in the summer.
Well, gardeners, you know, they always offer you all kinds of tips and secrets for growing great tomatoes, and now we've got one more here from an unusual source. Writing in the Journal of Agricultural and Food Chemistry, a group of researchers in Pisa, Italy, suggest irrigation with diluted sea water improves the nutritional value of cherry tomatoes.
That's right. Add just a little bit of salty sea water to it, sprinkling on the tomatoes there, and you should get better tomatoes, healthier tomatoes. Joining me now to talk about the work is one of the authors of the paper, Riccardo Izzo. He is a professor in the faculty of agriculture at the University Pisa in Pisa, Italy. Thank you for being with us this evening, Professor Izzo.
Dr. RICARDO IZZO (Agriculture, University of Pisa, Italy): Hello. Thank you to you.
FLATOW: How much salt water do you put in the tomatoes?
Dr. IZZO: We grow tomato plants with a concentration of a 12 percent of sea water.
FLATOW: Twelve percent of sea water. And why does the sea water increase and make the tomatoes better?
Dr. IZZO: This is because, in a thirst situation, a plant, I know, should choose to use energy for producing biomass or defend itself from oxidative damage, diverting its energy towards the production of secondary metabolites. And these metabolites protects the plants against the radicals. So if tomato are irrigated with this diluted sea water, and tomato is a moderate saline-tolerant species, it's ripened.
And we have proved this with the fact the level of this antioxidants increase. It is because the presence of these higher amount of antioxidants could be seen as a adaptive mechanism of tomato plants. It's used to counteract the (unintelligible) condition. And the consequent oxygen is damage. So, the plants protect itself.
FLATOW: So as a protection mechanism against the salt water, it makes antioxidants. What kinds of antioxidants?
Dr. IZZO: These antioxidants are represented by vitamin C, vitamin E, lipoic acid and phenous (ph). These are the major constituents of this antioxidant tool in tomato fruits.
FLATOW: So, can we all do this in our home, in our garden at home?
Dr. IZZO: Yes. I think so. The problem is that not all tomatoes, not all genotides (ph), respond in the same manner to the little water stress. And it's really - we have to take much attention to the salinity level of the water.
Because we have evidence that plants grow with 20 or 30 percent of salt, do not increase this antioxidants, but they die, they suffer damage because they cannot counteract these theoreticals that are produced. So it's possible to grow these plants or even in the house. But we have to be careful of how much salt we put in the water.
FLATOW: Yeah, that's a question we're getting from listener in Second Life, Bower,(ph) who writes, "How do you prevent the soil salination build-up? How do you know that, you know, if you keep putting salt water in there you're not going to put too much of it after awhile?"
Dr. IZZO: Yeah, but this is (unintelligible). The cultivation is not so easy because we grew plants in hydroponics, but it's under a controlled conditions - temperature, light, humidity. Otherwise, this is not possible to grow these plants at home if you don't control the conditions. It's not sufficient to have salty water.
Dr. IZZO: You have to monitor and control the all other parameters.
FLATOW: Right. James from the Netherlands on Second Life writes, "I wonder how you keep the salty taste away. Does the tomato pick up a saltier taste?"
Dr. IZZO: Yeah, there is a continuous circulation of diluted water that it's replaced every two hours up to 12 times per day. So we can control the salinity, the conductivity, the PH or the solution we add, nutrients, when we see that these are depleted because plants have taken them. So everything is controlled by a monitor, computer, that does this automatically.
FLATOW: So the plant itself, the tomato, the cherry tomato, is not going to taste saltier when you eat it?
Dr. IZZO: No, no, no. Of course not, because the taste of this tomato, it's a balance between sugar and organic acids. And this balance, it's - let's say, that it increase by the - increase the amount of organic acids and sugar. So these tomatoes are not salty, but yeah, I think they have a more flavor...
FLATOW: A better flavor.
Dr. IZZO: Sweeter.
FLATOW: Yeah. Can we do this with any cherry tomato or with any tomato that we want? Or is there a brand or a variety that you would recommend?
Dr. IZZO: No, I think it's not possible to do with all the types of tomato. For example, sour tomatoes are not very usable in this way. We use cherry tomatoes, the (unintelligible). And we also try to do this with other genotides that were constructed genetically, but we didn't succeed. So you have to choose on particular genotides, and we are now studying and try to find a more to cultivate. And more other species in just to have this in effect.
FLATOW: So you should not go into your garden and start sprinkling 12 percent salt water on your tomatoes? You might - they're not the laboratory kind that you have.
Dr. IZZO: Yeah. This is something that you can do in this moment only, in the lab. Or you have to grow this tomato in a big, green house. You need a big vessel so there you can grow this plant. Not possible how to do this with soil also because there is a problem that they arrive from (unintelligible) salinization of the soil.
Dr. IZZO: If you put diluted sea water on soil it's likely that you have not read a, physical, chemical characteristics of the soil onto it.
FLATOW: Yeah. Are there any other plants do you think that might work also with this?
Dr. IZZO: I know in this - melon has been the study for this purpose. And probably likely also watermelon can be - can give this same response. It is because we know that especially plants that are rich in water has this kind of response. I mean, plants that are rich in water and also sugar. So melon, or watermelon, can be a good candidates.
FLATOW: Yeah. So as a defense mechanism they make all these antioxidants. That's very interesting.
Dr. IZZO: The mechanics is the same. I mean, this is a general response of plants to oxidative stress. So, we have already observe this in other crops as wheat, Durham wheat, maize, and sunflower. These - (unintelligible) seeds and leaves, the mechanics that the plants used to protect itself, it's the same. It's a general one.
FLATOW: Yeah. So do you think you might be able to genetically engineer plants then that we could grow agriculturally, that could use brackish water or partially salty water?
Dr. IZZO: I think this is something that geneticists should study. The first thing is try to find the genotides that are rich in antioxidants. Then with stress, with the right kind of stress, we can increase these antioxidant levels, but the first step is to find or develop (unintelligible) that has a high and (unintelligible) antioxidant level.
FLATOW: Well, I want to thank you for taking time to be with us, Dr. Izzo.
Dr. IZZO: You are welcome.
FLATOW: Have a good evening and good weekend, Riccardo.
Dr. IZZO: Thank you, thank you so much.
FLATOW: You are welcome. Doctor Riccardo Izzo is professor in the faculty of agriculture at the University of Pisa in Pisa, Italy.