La vague de chaleur qui touche actuellement le sud de l’Europe met en péril la végétation et l’agriculture. Face à l’intensification de ces épisodes caniculaires, le monde agricole va devoir s’adapter.
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00:00 It's true that it's an exceptional heat wave for various reasons.
00:04 What you need to know is that plants and photosynthesis
00:10 have an optimum temperature, which is around 30°C.
00:20 And what happens is that when we exceed this temperature,
00:23 photosynthesis becomes less and less effective,
00:25 until it is reduced to almost zero, around 40°C.
00:28 This means that if we no longer have photosynthesis,
00:30 we no longer have productivity.
00:32 When we stay in temperatures around 40°C,
00:34 it's a reversible process.
00:36 When we leave the heat wave,
00:38 if the temperature drops, photosynthesis is put back in place.
00:41 On the other hand, when we exceed temperatures of 43°C, 44°C,
00:45 we start to have a phenomenon that is reversible,
00:47 because we have a destruction of the leaves due to the temperature.
00:50 And this becomes much more critical,
00:52 because in this case, the plants lose their leaves.
00:54 So obviously, it means that the impact will be much greater.
00:58 And in particular, it will continue after the heat wave.
01:01 And either the plants will have to re-manufacture leaves,
01:03 which will obviously cost them energy.
01:05 And then even in some cases, they will die,
01:07 because there are too many leaves that are impacted.
01:09 In general, when plants are well fed in water,
01:11 they sweat, like us, which allows them to regulate the temperature.
01:15 And so when they have enough water,
01:17 the evaporation of water consumes energy,
01:19 so it allows the temperature to drop.
01:21 And so plants, if they are well fed in water,
01:23 manage to maintain a temperature that will be 2-3°C above the air temperature.
01:28 (upbeat music)