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