How many calories does a plant photosynthesize per day?

[chingel]

Hello,

Related to a thought of why animals don't use photosynthesis (typical answer is that photosynthesis would provide only marginal energy compared to the needs of an animal), I am interested in how much energy does a plant produce using photosynthesis?

Any example or estimates is good to know, for example mediterranean climate and sun angle, clear day, calories per average leave per hour or per hour for m2 of leaves; or whatever else example anyone might have data for.

 

[phyzguy]

I got interested in this a few years ago, and compiled the attached spreadsheet on the energy gathered by various food crops, and how efficient they are at converting sunlight into food. I'd be interested in your comments.

 

[chingel]

That is a pretty low efficiency, but that is only how much of the energy the plant uses to grow the crops.

I have a question about the units, is the calories/kg row meant to be kilocalories? Why do you multiply it through by 10^6 to get megacalories, or is that row not meant to be kilocalories?

 

[phyzguy]

Both the Food value (cal/kg) and the Mcal/acre/year columns are in food calories (i.e. kilocalories). I just converted it to megacalories to make the numbers of order 1. When I converted to Watts, you see that I multiplied by 4.2*10^9 to convert mega-food-calories into Joules, so I think I've done it right.

You're right, this efficiency is just how efficient the crop is at producing human consumable food, but I think this is what you were asking about in your original post. If you look at all of the organic matter produced by the plant, I think the efficiency goes up to a few %, but I don't have those numbers.

 

[LudusRex]

I can provide some information about the amount of energy a plant produces through photosynthesis. The exact number of calories produced per day will vary depending on various factors such as the type of plant, environmental conditions, and the size of the plant. However, on average, a plant can produce about 100 calories of energy per day through photosynthesis. This may not seem like a lot compared to the energy needs of an animal, but it is important to remember that plants do not solely rely on photosynthesis for energy. They also use energy from the sun to grow and maintain their structures, which is essential for their survival.

To give a more specific example, let's consider a Mediterranean climate with a clear day and an optimal sun angle. In this scenario, a plant with an average leaf size can produce around 18-20 calories per hour through photosynthesis. This may seem like a small amount, but when you consider the fact that a plant has multiple leaves and can photosynthesize for several hours a day, the total amount of energy produced can add up significantly.

It is important to keep in mind that these are just estimates and the actual amount of energy produced can vary greatly depending on the specific conditions and characteristics of the plant. Additionally, plants also have different strategies for utilizing and storing energy, so the amount of energy produced through photosynthesis may not always directly translate to the amount of energy available for consumption.

In conclusion, while the amount of energy produced through photosynthesis may seem small compared to the needs of an animal, it is a vital process for the survival of plants and plays a crucial role in the overall functioning of ecosystems.