0:00:19.056,0:00:22.270 There is a very profound question 0:00:22.270,0:00:24.130 that you see on the screen. 0:00:24.130,0:00:31.097 If a tree falls in a forest -- and no one is around to hear it, 0:00:31.097,0:00:33.021 does it make a sound? 0:00:33.021,0:00:36.052 You all know this question and this question is attracting 0:00:36.052,0:00:40.313 the attention of philosophers for over a 300 years. 0:00:40.313,0:00:43.220 But this question, very question, would seem 0:00:43.220,0:00:47.803 totally ridiculous to the plants neighboring this tree, 0:00:47.804,0:00:51.126 which for many decades listened to messages 0:00:51.126,0:00:54.096 and signals coming from this fallen tree. 0:00:54.097,0:00:56.098 So today I'm going to tell you something 0:00:56.098,0:00:59.682 about plant communication 0:00:59.682,0:01:02.592 and something about the ways 0:01:02.592,0:01:06.138 plants learn from each other about their environment. 0:01:06.138,0:01:09.122 We all know something about that communication. 0:01:09.122,0:01:11.697 Plants communicate with animals all the time. 0:01:11.697,0:01:15.702 Not necessarily with fancy mammals like us 0:01:15.702,0:01:19.406 but more with little creatures like the insects 0:01:19.406,0:01:22.019 and the birds you see on the screen. 0:01:22.035,0:01:26.385 They attract them by putting out very flashy flowers 0:01:26.385,0:01:28.889 to make sure that they are pollinated. 0:01:28.889,0:01:31.451 This is part of their sex life. 0:01:31.451,0:01:34.298 This is one way they communicate. 0:01:34.298,0:01:35.796 Another way is to -- 0:01:35.796,0:01:40.730 They need some transition services for their seeds. 0:01:40.730,0:01:43.139 Therefore they make flashy fruits 0:01:43.139,0:01:46.454 and put some little sweet candies inside 0:01:46.454,0:01:50.547 so mammals and other creatures will carry them away 0:01:50.547,0:01:52.965 to new places, to new environments. 0:01:52.965,0:01:55.624 This is communication - look at the colors. 0:01:55.624,0:01:57.904 This is not only communicating with us. 0:01:57.904,0:02:00.417 This is communicating with very many other creatures. 0:02:00.417,0:02:04.262 But these are very simple ways 0:02:04.262,0:02:07.323 that the plants are taking 0:02:07.323,0:02:12.417 relying on the services made by animals. 0:02:12.417,0:02:14.533 This is all relying on the fact 0:02:14.533,0:02:16.833 that those animals have some brains. 0:02:16.833,0:02:19.327 They can decide whether to choose fruits, 0:02:19.327,0:02:21.116 whether to visit a flower. 0:02:21.116,0:02:23.955 This is using the brain of the animal. 0:02:23.955,0:02:27.283 There is some decision, motor, engine behind it. 0:02:27.283,0:02:30.272 Not of the plant - the animal. 0:02:30.272,0:02:35.119 But in our research, we are trying to do something else. 0:02:35.120,0:02:38.524 We try to find out whether plants can communicate 0:02:38.524,0:02:42.576 between themselves, with other plants. 0:02:42.576,0:02:46.375 And one nice example is by the phenomenon 0:02:46.375,0:02:47.979 we call talking trees. 0:02:47.979,0:02:53.155 This is not from our own studies but from other studies -- 0:02:53.155,0:02:58.077 other studies from the other laboratories around the world. 0:02:58.093,0:03:00.566 Trees are stuck in the same place - most of them. 0:03:00.566,0:03:03.132 Once they're germinated they are bound to stay there 0:03:03.132,0:03:04.747 for the rest of their lives. 0:03:04.762,0:03:06.883 Sometimes for hundreds of years. 0:03:06.883,0:03:08.596 They cannot run away 0:03:08.596,0:03:11.248 and this is making their lives very difficult because 0:03:11.248,0:03:14.218 there are very many creatures [who] are out to get them. 0:03:14.218,0:03:17.171 Many insects, mammals and other creatures 0:03:17.171,0:03:20.383 can simply come and bite their head off. 0:03:20.383,0:03:22.887 If they won't do anything good about it. 0:03:22.887,0:03:26.077 And one way - there are many ways the plants 0:03:26.077,0:03:28.666 defend themselves against this munching - 0:03:28.666,0:03:30.446 but one way is to put out 0:03:30.446,0:03:34.126 or to accumulate all kinds of nasty chemicals. 0:03:34.143,0:03:36.222 Once they have the chemicals, 0:03:36.222,0:03:39.025 they deter some of those grazers, herbivores - 0:03:39.025,0:03:42.510 all kinds of animals that want to munch on them. 0:03:42.510,0:03:46.185 And, in fact, they do something else too. 0:03:46.185,0:03:49.056 Once there is some munching on the plant, 0:03:49.056,0:03:53.404 some plants are capable of putting out 0:03:53.404,0:03:56.489 all kinds of odors - volatile materials, 0:03:56.489,0:04:00.038 which become airborne and picked up by other parts 0:04:00.038,0:04:03.836 of the same plant and other nearby neighbors. 0:04:03.836,0:04:07.149 Which, only when they get this message, 0:04:07.164,0:04:09.770 this communication from another plant, 0:04:09.770,0:04:11.907 start to produce toxins, 0:04:11.921,0:04:16.256 which deter any attack - by insects in this case. 0:04:16.271,0:04:19.760 This is pretty sophisticated behavior 0:04:19.760,0:04:23.048 for brainless creatures, I would say. 0:04:23.048,0:04:26.020 What else can they chat about? (Laughter) 0:04:26.020,0:04:29.622 And this is something that we are dealing with in our group. 0:04:29.647,0:04:33.606 We are asking specifically in one of our projects: 0:04:33.606,0:04:38.075 Can plants eavesdrop - listen to the hardships, 0:04:38.075,0:04:41.181 the stresses their neighbors undergo. 0:04:41.181,0:04:43.705 And use this information 0:04:43.705,0:04:47.031 to resist and survive better in the future. 0:04:47.031,0:04:49.635 Imagine the following situation. 0:04:49.635,0:04:53.239 There is a plant. Something bad happens to it - 0:04:53.239,0:04:58.201 stress like drought or high levels of salt - 0:04:58.201,0:05:02.654 we all know very well from this country, and it is stressed. 0:05:02.654,0:05:06.296 It is doing miserably. But now I am asking 0:05:06.312,0:05:08.328 whether a neighbor plant, which is totally 0:05:08.328,0:05:12.804 or seemingly oblivious to the stress of the other plant, 0:05:12.804,0:05:14.976 would sense the information, 0:05:14.976,0:05:18.135 get the communication and do something about it. 0:05:18.135,0:05:21.618 I am asking about the red arrow here. 0:05:21.618,0:05:24.991 So how do we do this? 0:05:24.991,0:05:28.919 All you need is a bunch of seed[ling]s 0:05:28.919,0:05:31.685 and a knife or a pair of scissors. 0:05:31.685,0:05:34.805 You cut off the root of a plant - 0:05:34.805,0:05:37.868 it would regenerate immediately many other roots. 0:05:37.868,0:05:40.457 And you can choose, carefully choose, which is very easy 0:05:40.457,0:05:44.002 to do for a five-year old, plants with only two roots. 0:05:44.002,0:05:46.849 And if they put out six, you take away four, 0:05:46.849,0:05:49.392 you leave them with two - more or less identical - 0:05:49.392,0:05:51.479 and you put them together like this: 0:05:51.495,0:05:54.731 sharing one pot in the middle. 0:05:54.731,0:05:57.214 Sharing a pot in the middle allows them 0:05:57.214,0:05:59.698 to communicate if they choose to do so. 0:05:59.698,0:06:03.658 This is allowing a route of communication between the roots. 0:06:03.682,0:06:05.798 Obviously, there is another channel for communication. 0:06:05.798,0:06:09.808 Among the leaves using the same mechanism 0:06:09.808,0:06:11.614 we were discussing before, 0:06:11.614,0:06:14.794 through [volatile chemicals] in the air. 0:06:14.825,0:06:16.536 So what can we do? 0:06:16.536,0:06:19.554 We just stress one root of one of the plants 0:06:19.554,0:06:22.009 and we ask - obviously we know that this guy 0:06:22.025,0:06:25.040 is going to be miserable about it - and we ask 0:06:25.040,0:06:28.292 whether the other guy will do something about it too. 0:06:28.292,0:06:31.069 OK? What do we measure? 0:06:31.069,0:06:34.047 We want something, which is simple to study, 0:06:34.047,0:06:38.326 simple to measure, and we want a rapid response - 0:06:38.326,0:06:41.563 something physiological, which is easy to pick up. 0:06:41.563,0:06:43.702 And one of those things is the way 0:06:43.702,0:06:47.071 plants keep their leaves open or close 0:06:47.071,0:06:50.120 when they are facing a problem. 0:06:50.120,0:06:51.938 What you see here, 0:06:51.938,0:06:55.694 thousands of times enlarged on the screen, 0:06:55.694,0:07:00.015 is little pores every plant has in its leaves 0:07:00.015,0:07:02.312 through which it is exchanging gas 0:07:02.312,0:07:04.667 with its environment. 0:07:04.670,0:07:08.935 These pores are openable, they are very flexible. 0:07:08.966,0:07:10.555 It's like little shutters - 0:07:10.555,0:07:13.687 they can close and open very-very swiftly - 0:07:13.687,0:07:18.614 through which they absorb CO2 and emit O2, oxygen. 0:07:18.614,0:07:20.738 By the way, which allows us 0:07:20.738,0:07:24.464 to resist and survive and to live on this planet. 0:07:24.464,0:07:27.960 So when the plant is happy, it is opening the stomata, 0:07:27.960,0:07:31.271 there is no outlook for any stress, 0:07:31.286,0:07:33.897 and this is how they look - open stomata. 0:07:33.897,0:07:36.659 Stomata are the little wholes. And when the plant 0:07:36.659,0:07:40.912 is unhappy, or expecting some problem, 0:07:40.912,0:07:44.947 for instance drought, it is closing those little pores. 0:07:44.947,0:07:47.417 And this is measurable, we can take a photograph 0:07:47.417,0:07:49.887 and measure it very easily. 0:07:49.887,0:07:53.480 So happy plants. We take a set of plants like this: 0:07:53.482,0:07:59.507 the one we are going to induce a stress to and a neighbor 0:07:59.507,0:08:01.932 and when there is no stress they are happy. 0:08:01.932,0:08:03.984 Nice and happy - look at the stomata - 0:08:03.984,0:08:06.560 they are smiling at you. 0:08:06.560,0:08:08.391 They are so happy about it. 0:08:08.391,0:08:12.401 But what if I stress - by draught - 0:08:12.401,0:08:15.028 one root of one of the plants? 0:08:15.028,0:08:17.348 It is miserable, closing its stomata, 0:08:17.348,0:08:19.919 the little holes, the little pores, 0:08:19.919,0:08:23.365 but also the neighbor - which was never harmed, 0:08:23.365,0:08:26.880 never stressed before - feels something. 0:08:26.880,0:08:31.707 There is communication. Why to eavesdrop? 0:08:31.707,0:08:34.179 Why should an unstressed neighbor 0:08:34.179,0:08:37.884 use such an information? It was not stressed! 0:08:37.884,0:08:42.303 Well, in many cases, if my neighbor is stressed now, 0:08:42.319,0:08:45.999 there is a very high chance that I am going to be stressed 0:08:45.999,0:08:48.062 in a few minutes, a few hours or a few days. 0:08:48.079,0:08:50.031 So better prepare for this. 0:08:50.031,0:08:52.340 Preparation for future is something 0:08:52.340,0:08:54.835 extremely important in the evolution 0:08:54.835,0:08:58.147 and in the ecology of any creature. 0:08:58.163,0:09:01.502 The more interesting and more difficult question is 0:09:01.502,0:09:03.950 why the stressed neighbor would allow 0:09:03.950,0:09:08.016 or give such information to its neighbors. 0:09:08.016,0:09:11.959 After all they can be its enemies, its competitors. 0:09:11.959,0:09:16.804 Well, in many cases plants are tremendously large. 0:09:16.804,0:09:20.698 They can be as large as a few football fields. 0:09:20.698,0:09:25.043 They can weigh hundreds of tons in biomass. 0:09:25.043,0:09:27.301 They can be tremendously large. 0:09:27.301,0:09:30.874 When attack is happening in one corner or one bunch, 0:09:30.889,0:09:33.033 there is a very good rationale 0:09:33.033,0:09:36.243 to disperse the information to the rest of the plant. 0:09:36.243,0:09:39.606 Some of them can be large by cloning. 0:09:39.606,0:09:43.078 They have many twin parts which spread over 0:09:43.078,0:09:46.992 like in the lawn grasses in your back yard. 0:09:46.992,0:09:50.790 Or the strawberries you eat. Or the birch trees. 0:09:50.790,0:09:53.711 They are all clonal. They have very many members 0:09:53.711,0:09:55.542 which are connected together. 0:09:55.542,0:09:58.908 Some of which are severed from each other, disconnected. 0:09:58.919,0:10:04.346 So it's a good idea to disperse the news, the warning. 0:10:04.346,0:10:10.285 Stress is happening. So if this logic is correct, 0:10:10.300,0:10:13.812 I would expect something even more elaborate. 0:10:13.812,0:10:20.584 That a non-stressed plant would share the information with its neighbors. 0:10:20.584,0:10:23.219 Not only the stressed plant would share, but also 0:10:23.220,0:10:26.111 the unstressed neighbor would share the information 0:10:26.111,0:10:29.428 with further, with more neighbors. OK? 0:10:29.428,0:10:31.839 Testing it is simple. Now you know the method, 0:10:31.839,0:10:34.250 you can be a scientist as me. 0:10:34.250,0:10:36.059 You take this system, which we already know 0:10:36.059,0:10:38.790 what happens in - the first neighbor is responding, 0:10:38.790,0:10:40.549 there is communication, 0:10:40.549,0:10:42.401 and we simply add more neighbors. 0:10:42.401,0:10:44.119 And we ask the same question. 0:10:44.134,0:10:47.338 Would this information be relayed to them? 0:10:47.338,0:10:50.771 Would this unstressed neighbor share the information 0:10:50.771,0:10:53.223 with additional neighbors? 0:10:53.223,0:10:58.811 And this is after fifteen minutes. Fifteen short minutes! 0:10:58.811,0:11:01.743 Three plants were closing their stomata. 0:11:01.743,0:11:03.213 So there was relay, 0:11:03.213,0:11:06.479 there was sharing by unstressed plants. 0:11:06.479,0:11:11.191 And in on hour only, all five plants in a row, 0:11:11.191,0:11:13.380 and if I would work hard enough, 0:11:13.380,0:11:14.900 and my people would work hard enough, 0:11:14.900,0:11:19.077 I bet you it would reach the tenth plant too. 0:11:19.077,0:11:22.674 So there is both communication and sharing 0:11:22.674,0:11:26.180 of the information by unstressed individuals here. 0:11:26.180,0:11:30.573 This is all by plants having no brains - remember that! 0:11:30.573,0:11:34.979 So far so good, but we've been showing 0:11:34.980,0:11:38.512 the communication and the sharing of the information 0:11:38.512,0:11:41.745 but we haven't proven yet that this was happening 0:11:41.761,0:11:43.892 through the root communication. 0:11:43.892,0:11:47.797 This was all done by a system sharing roots, right? 0:11:47.797,0:11:51.791 In order to prove or to test whether it was through the root 0:11:51.791,0:11:54.657 or through the shoots, the leaves above ground, 0:11:54.657,0:11:59.997 through volatile chemicals, we have to add another set 0:11:59.997,0:12:03.248 of plants which were not sharing the roots. 0:12:03.248,0:12:05.854 And, indeed, when plants are not sharing the roots, 0:12:05.854,0:12:08.460 there is no communication in this case. 0:12:08.460,0:12:10.832 Which is a direct proof that communication 0:12:10.832,0:12:16.164 of such stress signals is going between the roots. 0:12:16.164,0:12:20.412 But there is a more profound question here. After all, 0:12:20.412,0:12:27.028 stomata, as I already declared, work extremely rapidly. 0:12:27.028,0:12:29.202 They can open and close in a few seconds, 0:12:29.202,0:12:31.813 in a few minutes, they can reopen 0:12:31.813,0:12:34.638 after a few seconds, a few moments. 0:12:34.638,0:12:37.233 And indeed this is what they are doing 0:12:37.233,0:12:41.736 after getting the "cry wolf" warning signals. 0:12:41.736,0:12:44.732 So this is a little fishy or might be fishy, 0:12:44.732,0:12:46.869 maybe it's not so essential, 0:12:46.869,0:12:50.082 maybe it's not significant for the real life. 0:12:50.082,0:12:52.771 And the profound question here is to ask 0:12:52.771,0:12:56.413 whether plants would learn from their past experiences 0:12:56.429,0:13:00.576 and counter with a stressed plant and get better 0:13:00.576,0:13:04.676 in facing and surviving hardships in the future - 0:13:04.676,0:13:06.673 in this case a drought. 0:13:06.673,0:13:08.731 And the way to test this is very simple. 0:13:08.731,0:13:12.359 You take the very same system you already know. 0:13:12.359,0:13:17.509 A row of plants sharing the root systems in the dirt pots: 0:13:17.509,0:13:19.871 in one case you don't stress them, 0:13:19.871,0:13:22.107 and in another case you do stress. 0:13:22.107,0:13:23.745 What do we stress and not stress? 0:13:23.745,0:13:27.253 One root of one plant in the row. That's it! 0:13:27.253,0:13:30.691 And then we expose the entire system to real drought. 0:13:30.691,0:13:33.423 And here is the real test! 0:13:33.423,0:13:37.778 In real life, not just blinking your pores, right? 0:13:37.778,0:13:40.183 In real life. 0:13:40.183,0:13:42.131 So this is the happy plant, 0:13:42.131,0:13:45.649 which never got any exposure to stressed neighbor, 0:13:45.649,0:13:48.070 and after one month it's bone dry! 0:13:48.070,0:13:51.541 As would be expected in Israeli green-house 0:13:51.541,0:13:53.352 40 °C degrees in summer. 0:13:53.352,0:13:56.240 OK, this is not surprising anyone here. 0:13:56.240,0:14:00.000 But this guy, this set, got one of the roots 0:14:00.000,0:14:02.452 of one of the plants exposed to drought 0:14:02.452,0:14:04.438 before the experiment started, 0:14:04.438,0:14:07.054 before the exposure to drought started. 0:14:07.054,0:14:12.134 And one month later, this is how it looks! 0:14:12.134,0:14:14.667 This is not by giving it more water! 0:14:14.667,0:14:18.046 This is by the plants getting an experience, 0:14:18.046,0:14:21.220 the communicative experience, of facing a neighbor 0:14:21.220,0:14:24.985 that once in the past was exposed to drought, 0:14:24.985,0:14:27.869 using the information, storing it somehow 0:14:27.869,0:14:30.000 and using it later in life 0:14:30.000,0:14:33.218 and better survive and resist drought in the future. 0:14:33.218,0:14:36.086 This is both learning and memory 0:14:36.086,0:14:38.723 of brainless creatures. 0:14:38.723,0:14:40.092 And this is a big lesson! 0:14:40.092,0:14:43.215 The lesson is from the humble creatures 0:14:43.215,0:14:48.721 which have no brain but can learn, memorize 0:14:48.721,0:14:51.755 and use the environmental information later on 0:14:51.755,0:14:53.974 for better survivorship. 0:14:53.974,0:14:57.123 I want to thank the members of my lab: 0:14:57.123,0:14:59.902 Dr. Omer Falik, who over-viewed the process 0:14:59.902,0:15:04.109 and most of the experiments, Ishay Hoffman, 0:15:04.109,0:15:07.836 Yonat Mordoch, Daniel Ben-Natan Sion, 0:15:07.836,0:15:10.473 Miri Vanunu and Oron Goldstein; 0:15:10.473,0:15:13.545 and the generous financial support 0:15:13.545,0:15:15.581 of the Israel Science Foundation. 0:15:15.581,0:15:17.167 Thank you very much! 0:15:17.167,3:59:59.000 (Applause)