What Is Photosynthesis? How Does Photosynthesis Work? Why Is Photosynthesis Important? Does Removing Leaves Limit Photosynthesis & Growth? This Article Answers Those Vital Questions.
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I frequently see questions online about photosynthesis and how we should remove leaves from plants to “put the energy in to the fruit”. Photosynthesis is what produces the “energy” and without leaves there can be no energy to put in to the fruit. And even if were remove some leaves the amount of energy will be reduced and so will growth. It really is the simple.
But lets start with the basics of what photosynthesis is, look at a video on it and then consider the impact of reduced photosynthesise .. and at the end, if you’ve the inclination, look at some science.
What Is Photosynthesis?
Look at any dictionary and they will give the same answer, though sometimes the words used vary a bit!
Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
Oxford Languages
How Does Photosynthesis Work?
It’s quite simple. The plant takes in carbon dioxide from the air. Then sunlight acts on the air and the water the plant has taken in via its roots. Oxygen and glucose is produced. The video below shows this in more detail.
In the next step the glucose (sugar) and various nutrients from the soil are combined to produce organic matter such as stems, roots, flowers, fruit etc. More on that in another post.
Photosynthesis: Limiting Factors
Carbon Dioxide is needed for photosynthesis to take place. Without it nothing happens. There was a time when commercial growers added CO2 to their greenhouses as optimum photosynthesis takes place when the CO2 level its higher than the naturally occurring level at that time. Since then we have seen global warming and the CO2 levels don’t need raising. We are only talking a few hundred parts per million (ppm), but that is all that is needed.
Water is essential for the process to take place and during periods of drought the lack of water can be a limiting factor.
Chlorophyll is present in all green plants and is responsible for the absorption of light energy which usually comes from sunlight.
Light is really important. Sunlight is the main source employed and there e has to be enough of it. When the weather is cloudy, the area is shaded and the days shorter in winter we see less sunlight and hence energy available for the plants. It is why plants “etiolate” (get drawn) when light is short. The plant is looking for the light.
Temperature is the controlling factor in many cases. For effective photosynthesis we need adequate warmth. If it is too cool the chemical processes are slowed down. And if it is too hot the proteins denature (sort of like in cooking) and the process stops. Different plants have different temperature requirements but a simple way to remember the needs of most of them is to say it should be around “room temperature”.
The reality is the above all work in unison. If one is missing or substandard in any way the whole process is limited by it. For example, if it is too cold the process slows down or stops, depending on the temperature. If there isn’t enough light, again it all slows down. So cold cloudy days are slow growing days and warm sunny days we see more growth, PROVIDED all the other elements are there as required.
Why Is Photosynthesis Important?
The above questions and answers gives us the all we need to know here. But let’s reiterate.
Photosynthesis is essential for plant growth. Without photosynthesis we get no growth. And without leaves we get no photosynthesis.
Growth depends on photosynthesis.
Does Removing Leaves Limit Photosynthesis & Growth?
Yes. Without any shadow of doubt.
Removing leaves reduces the plant’s ability;ity to produce sugars and therefore to grow. every leaf is important and I rarely subscribe to the idea we need to remove leaves to increase airflow in tomato crops. The way to increase airflow isn’t to remove leaves, it is to ventilate the greenhouse or polytunnel. And if there aren’t enough windows or air vents the solution is to add more. In my own amateur greenhouse I remove the triangular piece of glass at the top of each end wall. That allows the air to flow freezer. If that isn’t enough then remove more glass, from the end walls or sidewalks as appropriate. They are easy to remove and easy to replace when winter comes (though I permanently remove the triangular piece at the gable ends on my greenhouse. It allows winter gales to blow through should a pane ever break .. though broken panes aren’t a regular occurrence in my greenhouse).
More Facts On Photosynthesis & Leaves
To be strictly accurate, it’s not true that it’s only the leaves that can photosynthesis. Any part of the plant that contains chlorophyll can. Technically that includes the stems and even green fruit. But the ability is very limited and if all the leaves were removed it might keep the plant alive but don’t expect growth based purely on this fact.
Another little known fact is that the leaves at the top of a tomato carry out more photosynthesis than those lower down. Around 80% will take place in the upper leaves. BUT that is no reason to get rid of the bottom leaves. They are still functioning and it isn’t that they have lost the ability to photosynthesise , they just aren’t getting enough light because the leaves above shade them.
I’ve written more on how to grow tomatoes and how to deleaf tomatoes elsewhere.
The thing is we cannot expect to get maximum growth if we lose the ability to produce 20% of the sugars that are needed for growth. It’s a bit like expecting a marathon runner to do their best time whilst wearing a mask that inhibits breathing.
With tomatoes we can remove a few leaves to help us see the crop when picking, but to remove more reduces the yield AND the flavour of the fruit.
What is the Equation for Photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2
Photosynthesis: The Video
Tag: What Is Photosynthesis? Is Photosynthesis Important?
Photo Attribution: Jon Sullivan, Public domain, via Wikimedia Commons
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