---
title: "Photosynthesis and Limiting Factors"
description: "Light intensity, carbon dioxide concentration and temperature each set a ceiling on the rate of photosynthesis, and at any moment one of them is the limiting factor. Includes the inverse square relati"
canonical: https://lightmysky.com/learn/science/photosynthesis-and-limiting-factors-mt_PDn831oIih
source: https://lightmysky.com/learn/science/photosynthesis-and-limiting-factors-mt_PDn831oIih.md
retrieved: 2026-09-12
---

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# Photosynthesis and Limiting Factors

Light intensity, carbon dioxide concentration and temperature each set a ceiling on the rate of photosynthesis, and at any moment one of them is the limiting factor. Includes the inverse square relation between lamp distance and light intensity.

Subject: Science · Area: Organisms & Life Processes · Ages 15 to 16
Page: https://lightmysky.com/learn/science/photosynthesis-and-limiting-factors-mt_PDn831oIih

## Ready when they can

- Reads a rate graph and names the limiting factor in each region of the curve.
- Uses the inverse square relation to say what moving a lamp twice as far away does to light intensity.
- Explains why a greenhouse grower may add carbon dioxide rather than more light.

## Lesson: What holds the leaf back

Light, carbon dioxide and temperature each set a ceiling on photosynthesis, so a grower who wants more food finds which one limits the rate. Read the graph in regions: where the line climbs, the thing on the axis limits. Where it flattens, something else holds it down.

**Example.** Light obeys the inverse square rule. Move a lamp from 1 metre to 2 metres and the leaf gets a quarter of the light. At 800 lux from 1 metre, moving to 4 metres leaves 50 lux, since 4 squared is 16.

Raise one ceiling and the rate climbs until the next factor bottlenecks. That is why a grower adds carbon dioxide when light is already plenty. Push heat too far and the enzymes running the reaction fail instead.

**Tip.** Remember the net rate too: photosynthesis builds sugar while respiration burns some, and leftover sugar becomes growth. A limit on the leaf is a limit on the whole plant.

**Recap.** Find the flat part, name the ceiling behind it, and raise that one before touching the rest.

## Practice

11 questions on this page, each with its working shown.

## Needs first

- [Measuring the Rate of an Enzyme Reaction](https://lightmysky.com/learn/science/measuring-the-rate-of-an-enzyme-reaction-mt_Rmz54ICmRC)
- [Photosynthesis](https://lightmysky.com/learn/science/photosynthesis-mt_zM5vu31jgl)

## Opens up

- [Light-Dependent Reactions in the Thylakoid Membrane](https://lightmysky.com/learn/science/light-dependent-reactions-in-the-thylakoid-membrane-mt_3Ooq3BfmpX)
- [Respiration: Energy Yield, Oxygen Debt and Fermentation](https://lightmysky.com/learn/science/respiration-energy-yield-oxygen-debt-and-fermentation-mt_mvnCjThdTH)
- [Food Security: What Limits Yield and What It Costs to Raise It](https://lightmysky.com/learn/science/food-security-what-limits-yield-and-what-it-costs-to-raise-it-mt_SprRvGuyrK)