[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.96,0:00:08.41,Default,,0000,0000,0000,,In the 18th Century,
Dialogue: 0,0:00:08.41,0:00:13.21,Default,,0000,0000,0000,,Swedish botonist Carolus Linnaeus\Ndesigned the flower clock,
Dialogue: 0,0:00:13.21,0:00:16.47,Default,,0000,0000,0000,,a timepiece made of flowering plants
Dialogue: 0,0:00:16.47,0:00:20.66,Default,,0000,0000,0000,,that bloom and close \Nat specific times of day.
Dialogue: 0,0:00:20.66,0:00:25.03,Default,,0000,0000,0000,,Linnaeus's plan wasn't perfect,\Nbut the idea behind it was correct.
Dialogue: 0,0:00:25.03,0:00:29.36,Default,,0000,0000,0000,,Flowers can indeed sense time,\Nafter a fashion.
Dialogue: 0,0:00:29.36,0:00:33.76,Default,,0000,0000,0000,,Mornings glories unfurl their petals\Nlike clockwork in the early morning.
Dialogue: 0,0:00:33.76,0:00:38.03,Default,,0000,0000,0000,,A closing white water lily \Nsignals that it's late afternoon,
Dialogue: 0,0:00:38.03,0:00:43.34,Default,,0000,0000,0000,,and moon flowers, as the name suggests,\Nonly bloom under the night sky.
Dialogue: 0,0:00:43.34,0:00:46.78,Default,,0000,0000,0000,,But what gives plants \Nthis innate sense of time?
Dialogue: 0,0:00:46.78,0:00:48.67,Default,,0000,0000,0000,,It's not just plants, in fact.
Dialogue: 0,0:00:48.67,0:00:51.89,Default,,0000,0000,0000,,Many organisms on Earth\Nhave a seemingly inherent awareness
Dialogue: 0,0:00:51.89,0:00:54.99,Default,,0000,0000,0000,,of where they are in the day's cycle.
Dialogue: 0,0:00:54.99,0:00:57.22,Default,,0000,0000,0000,,That's because of circadian rhythms,
Dialogue: 0,0:00:57.22,0:01:02.29,Default,,0000,0000,0000,,the internal timekeepers\Nthat tick away inside many living things.
Dialogue: 0,0:01:02.29,0:01:06.75,Default,,0000,0000,0000,,These biological clocks allow organisms\Nto keep track of time
Dialogue: 0,0:01:06.75,0:01:11.02,Default,,0000,0000,0000,,and pick up on environmental cues\Nthat help them adapt.
Dialogue: 0,0:01:11.02,0:01:14.23,Default,,0000,0000,0000,,That's important, because the planet's\Nrotations and revolutions
Dialogue: 0,0:01:14.23,0:01:17.26,Default,,0000,0000,0000,,put us in a state of constant flux,
Dialogue: 0,0:01:17.26,0:01:21.01,Default,,0000,0000,0000,,although it plays out in a repetitive,\Npredictable way.
Dialogue: 0,0:01:21.01,0:01:23.71,Default,,0000,0000,0000,,Circadian rhythms incorporate various cues
Dialogue: 0,0:01:23.71,0:01:27.50,Default,,0000,0000,0000,,to regulate when an organism \Nshould wake and sleep,
Dialogue: 0,0:01:27.50,0:01:30.03,Default,,0000,0000,0000,,and perform certain activities.
Dialogue: 0,0:01:30.03,0:01:34.56,Default,,0000,0000,0000,,For plants, light and temperature\Nare the cues which trigger reactions
Dialogue: 0,0:01:34.56,0:01:37.26,Default,,0000,0000,0000,,that play out at a molecular scale.
Dialogue: 0,0:01:37.26,0:01:42.05,Default,,0000,0000,0000,,The cells in stems, leaves, and flowers\Ncontain phytochromes,
Dialogue: 0,0:01:42.05,0:01:45.04,Default,,0000,0000,0000,,tiny molecules that detect light.
Dialogue: 0,0:01:45.04,0:01:49.85,Default,,0000,0000,0000,,When that happens, phytochromes\Ninitiate a chain of chemical reactions,
Dialogue: 0,0:01:49.85,0:01:53.49,Default,,0000,0000,0000,,passing the message down \Ninto the cellular nuclei.
Dialogue: 0,0:01:53.49,0:01:57.50,Default,,0000,0000,0000,,There, transcription factors trigger\Nthe manufacture of proteins
Dialogue: 0,0:01:57.50,0:02:01.26,Default,,0000,0000,0000,,required to carry out \Nlight-dependent processes,
Dialogue: 0,0:02:01.26,0:02:03.25,Default,,0000,0000,0000,,like photosynthesis.
Dialogue: 0,0:02:03.25,0:02:07.01,Default,,0000,0000,0000,,These phytochromes not only sense\Nthe amount of light the plant receives,
Dialogue: 0,0:02:07.01,0:02:09.38,Default,,0000,0000,0000,,but can also detect tiny differences
Dialogue: 0,0:02:09.38,0:02:13.78,Default,,0000,0000,0000,,in the distribution of wavelengths \Nthe plant takes in.
Dialogue: 0,0:02:13.78,0:02:15.64,Default,,0000,0000,0000,,With this fine tuned sensing,
Dialogue: 0,0:02:15.64,0:02:18.57,Default,,0000,0000,0000,,phytochromes allow the plant\Nto discern both time,
Dialogue: 0,0:02:18.57,0:02:21.81,Default,,0000,0000,0000,,the difference between \Nthe middle of the day and the evening,
Dialogue: 0,0:02:21.81,0:02:26.05,Default,,0000,0000,0000,,and place, whether \Nit is in direct sunlight or shade,
Dialogue: 0,0:02:26.05,0:02:30.93,Default,,0000,0000,0000,,enabling the plant to match\Nits chemical reactions to its environment.
Dialogue: 0,0:02:30.93,0:02:33.09,Default,,0000,0000,0000,,This makes for early risers.
Dialogue: 0,0:02:33.09,0:02:37.20,Default,,0000,0000,0000,,A few hours before sunrise,\Na typical plant is already active,
Dialogue: 0,0:02:37.20,0:02:42.14,Default,,0000,0000,0000,,creating MRNA templates \Nfor its photosynthesizing machinery.
Dialogue: 0,0:02:42.14,0:02:44.68,Default,,0000,0000,0000,,As the phytochromes \Ndetect increasing sunlight,
Dialogue: 0,0:02:44.68,0:02:47.25,Default,,0000,0000,0000,,the plant readies \Nits light-capturing molecules
Dialogue: 0,0:02:47.25,0:02:51.71,Default,,0000,0000,0000,,so it can photosynthesize\Nand grow throughout the morning.
Dialogue: 0,0:02:51.71,0:02:53.58,Default,,0000,0000,0000,,After harvesting their morning light,
Dialogue: 0,0:02:53.58,0:02:57.37,Default,,0000,0000,0000,,plants use the rest of the day\Nto build long chains of energy
Dialogue: 0,0:02:57.37,0:03:01.15,Default,,0000,0000,0000,,in the form of glucose polymers, \Nlike starch.
Dialogue: 0,0:03:01.15,0:03:04.04,Default,,0000,0000,0000,,The sun sets, and the day's work is done,
Dialogue: 0,0:03:04.04,0:03:07.58,Default,,0000,0000,0000,,though a plant is anything \Nbut inactive at night.
Dialogue: 0,0:03:07.58,0:03:09.12,Default,,0000,0000,0000,,In the absence of sunlight,
Dialogue: 0,0:03:09.12,0:03:11.18,Default,,0000,0000,0000,,they metabolize and grow,
Dialogue: 0,0:03:11.18,0:03:15.41,Default,,0000,0000,0000,,breaking down the starch from \Nthe previous day's energy harvest.
Dialogue: 0,0:03:15.41,0:03:18.24,Default,,0000,0000,0000,,Many plants have seasonal rhythms as well.
Dialogue: 0,0:03:18.24,0:03:20.34,Default,,0000,0000,0000,,As spring melts the winter frost,
Dialogue: 0,0:03:20.34,0:03:24.41,Default,,0000,0000,0000,,phytochromes sense the longer days\Nand increasing light,
Dialogue: 0,0:03:24.41,0:03:28.68,Default,,0000,0000,0000,,and a currently unknown mechanism\Ndetects the temperature change.
Dialogue: 0,0:03:28.68,0:03:31.32,Default,,0000,0000,0000,,These systems pass the news\Nthroughout the plant
Dialogue: 0,0:03:31.32,0:03:33.67,Default,,0000,0000,0000,,and make it produce blooming flowers
Dialogue: 0,0:03:33.67,0:03:37.58,Default,,0000,0000,0000,,in preparation for the pollinators\Nbrought out by warmer weather.
Dialogue: 0,0:03:37.58,0:03:41.98,Default,,0000,0000,0000,,Circadian rhythms act as link\Nbetween a plant and its environment.
Dialogue: 0,0:03:41.98,0:03:45.09,Default,,0000,0000,0000,,These oscillations come \Nfrom the plants themselves.
Dialogue: 0,0:03:45.09,0:03:47.56,Default,,0000,0000,0000,,Each one has a default rhythm.
Dialogue: 0,0:03:47.56,0:03:50.81,Default,,0000,0000,0000,,Even so, these clocks \Ncan adapt their oscillations
Dialogue: 0,0:03:50.81,0:03:53.92,Default,,0000,0000,0000,,to environmental changes and cues.
Dialogue: 0,0:03:53.92,0:03:55.85,Default,,0000,0000,0000,,On a plant that's in constant flux,
Dialogue: 0,0:03:55.85,0:04:00.76,Default,,0000,0000,0000,,it's the circadian rhythms that enable\Na plant to stay true to its schedule
Dialogue: 0,0:04:00.76,0:04:03.14,Default,,0000,0000,0000,,and to keep its own time.