5 ms·

How can that be right? 20c is on the low end of room temperature. So a plant is actually bad at photosynthesising when it’s warm and there’s the most sunlight?

How can that be right? 20c is on the low end of room temperature. So a plant is actually bad at photosynthesising when it’s warm and there’s the most sunlight? Why? Wouldn’t this mean greenhouses are BAD for plants?

krageon 7y ago
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC396144/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC396144/ Is the closest thing to a real source I could find at short notice. I found this surprising as well, I guess it merits some more casual research!
adrianN 7y ago
Plants evaporate a lot of water, so their leaves are likely a bit cooler than ambient temperatures.
dTal 7y ago
Yeah, I don't believe this at all. In Florida for instance the daily high never really goes below 20C all year, and the name literally means "flowery". 40C I might believe, but 20? No way.
novok 7y ago
Yeah I agree. Vast parts of jungle land is consistently around 25-30C, surely the plants there are adapted for that?
noselasd 7y ago
And that 20C is in the shade, while foilage is typically exposed directly to the sun, at significantly higher temperatures.
sedachv 7y ago
> So a plant is actually bad at photosynthesising when it’s warm and there’s the most sunlight? Yes. That is one of the big reasons why it is difficult to grow crops in desert regions even with irrigation. > Why? Thermal properties of chemical reactions. There is a very narrow range of temperatures at which the chemical reactions needed for plant life and growth can occur. The space of possible chemical reactions are limited by the availability and distributions of various elements and molecules in the environment that the plant has available, so there is not going to be a magic evolution or breeding of heat-tolerant crops that will violate these chemical constraints. > Wouldn’t this mean greenhouses are BAD for plants? Greenhouses are not "tropical desert hot houses." They are used to boost temperature in cold climates for the specific crops that are grown. Tomatoes like 25 degrees Celsius, but, for example, lettuce will not grow if it is above 21 degrees Celsius.

krageon 7y ago

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC396144/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC396144/ Is the closest thing to a real source I could find at short notice. I found this surprising as well, I guess it merits some more casual research!

adrianN 7y ago

Plants evaporate a lot of water, so their leaves are likely a bit cooler than ambient temperatures.

dTal 7y ago

Yeah, I don't believe this at all. In Florida for instance the daily high never really goes below 20C all year, and the name literally means "flowery". 40C I might believe, but 20? No way.

novok 7y ago

Yeah I agree. Vast parts of jungle land is consistently around 25-30C, surely the plants there are adapted for that?

noselasd 7y ago

And that 20C is in the shade, while foilage is typically exposed directly to the sun, at significantly higher temperatures.

sedachv 7y ago

> So a plant is actually bad at photosynthesising when it’s warm and there’s the most sunlight? Yes. That is one of the big reasons why it is difficult to grow crops in desert regions even with irrigation. > Why? Thermal properties of chemical reactions. There is a very narrow range of temperatures at which the chemical reactions needed for plant life and growth can occur. The space of possible chemical reactions are limited by the availability and distributions of various elements and molecules in the environment that the plant has available, so there is not going to be a magic evolution or breeding of heat-tolerant crops that will violate these chemical constraints. > Wouldn’t this mean greenhouses are BAD for plants? Greenhouses are not "tropical desert hot houses." They are used to boost temperature in cold climates for the specific crops that are grown. Tomatoes like 25 degrees Celsius, but, for example, lettuce will not grow if it is above 21 degrees Celsius.