---
title: "Plants Are Producers"
book: "Primary & Middle School Biology"
subject: biology
language: en
chapter: 40
exercises: 12
source: https://one-course.com/books/biology/1/en/chapter/40-plants-are-producers
---

# Chapter 40 — Plants Are Producers

Weigh a watered pot, [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) an acorn in it, and come back after years to weigh the young oak: kilograms of wood, bark, [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) and [root](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) — while the pot’s soil has scarcely lost a gram ([Example 22.7](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#ex-g4-what-plants-need-tree) first sprang this surprise). Kilograms of tree, made from what? This chapter pins the answer down — and names the [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’ unique trade.

## 40.1 Organic and mineral matter

**Definition 40.1 (Mineral and organic matter).**

Matter, for a biologist, comes in two kinds:

- *mineral matter* : matter of the non-living world — water, air’s gases, rock, the dissolved [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) of [Proposition 22.3](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) ;
- *organic matter* : matter made by [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) and composing their bodies — wood, [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) , [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) , fat, sugar, wool. Burnable, rottable, and always traceable to a living maker.

**Example 40.2 (Sorting a pocketful).**

From a coat pocket after a walk: a pebble — mineral; a hazelnut — organic (a hazel made it); a plastic button — organic by origin, oddly enough (plastics are made from oil, the transformed remains of ancient [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components)); a drop of rain — mineral; a woolly glove — organic (a sheep made the wool).

## 40.2 The producers’ trade

**Proposition 40.3 (Plants produce organic matter from mineral matter).**

A green [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant), given only *mineral* ingredients — water and dissolved salts from the soil, a gas taken from the *air* — and the [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) of *[light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions)*, makes *organic* matter: its own sugar, and from it wood, [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) and [root](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts). This making is the trade [Proposition 22.6](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-make) promised to explain: [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) are *producers* — the only makers of new [organic matter](#def-g6-plants-are-producers-matter) from purely mineral supplies. The green substance of the [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) is the light-catching machinery; the manufacture happens in the [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), by day.

**Proof.** *Admitted at this level.* ∎

![The producers’ trade: mineral inputs and light in, organic matter out. Only green plants (and their green relatives) run this manufacture.](https://one-course.com/images/onecourse/chapters/biology-1/g6-plants-are-producers/fig-dbbbb108661c.svg)

*The [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’ trade: mineral inputs and [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) in, [organic matter](#def-g6-plants-are-producers-matter) out. Only green [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) (and their green relatives) run this manufacture.*

**Example 40.4 (The evidence, assembled).**

Three earlier observations now click together. The weighed pot: the oak’s kilograms did not come from the soil — they came mostly from air and water. The pale prisoner of [Example 22.4](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#ex-g4-what-plants-need-pale): no [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), no manufacture — the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) starves in the dark with a full larder of minerals. The mineral-starved mint of [Exercise 22.11](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#exo-g4-what-plants-need-11): salts are needed — but as small supplies, not as the bulk. Bulk from air and water, [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) from [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), seasoning from the soil.

**Remark 40.5 (The gas swap, both ways).**

The air gas the [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) takes in is *carbon dioxide* — the very gas every breather exhales ([Proposition 26.5](https://one-course.com/books/biology/1/en/chapter/26-breathing#prop-g4-breathing-exchange)); and manufacturing releases *oxygen* to the air — the very gas every breather needs. [Plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) also breathe, day and night, like all [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components); but by day a working [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts)’s manufacture far outruns its [breathing](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements). The world’s breathable air is the [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’ by-product — one more debt every [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) owes the green.

## 40.3 Producers feed everyone — and store for themselves

**Proposition 40.6 (The first link, explained).**

[Proposition 19.3](https://one-course.com/books/biology/1/en/chapter/19-food-chains#prop-g3-food-chains-start) decreed every [food chain](https://one-course.com/books/biology/1/en/chapter/19-food-chains#def-g3-food-chains-chain) starts with a [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant); now the decree has its reason. Only [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) make [organic matter](#def-g6-plants-are-producers-matter) from [mineral matter](#def-g6-plants-are-producers-matter); every [consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) ([Definition 34.3](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)) can only *transform* [organic matter](#def-g6-plants-are-producers-matter) it eats. So all the [organic matter](#def-g6-plants-are-producers-matter) in every living body — rabbit, fox, buzzard, you — was first manufactured in a [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), and the food pyramid of [Proposition 34.5](https://one-course.com/books/biology/1/en/chapter/34-food-webs#prop-g5-food-webs-pyramid) stands on the green floor because that is where matter enters the living world.

**Proof.** *Admitted at this level.* ∎

**Example 40.7 (The plant’s own pantry).**

What a [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) makes beyond the day’s needs, it stores as organic reserves: the potato [tuber](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber) and tulip [bulb](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber) ([Example 24.7](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber)), the bean’s thick halves ([Definition 9.1](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed)), the carrot’s fat [root](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) ([Exercise 3.10](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#exo-g1-plants-around-us-10)), the sweetness of the beet. Every one is summer [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), banked as matter — and every one is exactly what farmers, and eaters, harvest.

**Method 40.8 (Tracing any food to its leaf).**

Take any food on the table:

1. if it is [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) matter — bread’s wheat, the potato, the apple — it is [producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) ’s manufacture directly: name the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) and its stored organ;
2. if it is [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) matter — cheese, [egg](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) , ham — step down the chain: what did the [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) eat? and that food’s maker? continue to the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) ;
3. write the chain with arrows ( [Definition 19.1](https://one-course.com/books/biology/1/en/chapter/19-food-chains#def-g3-food-chains-chain) );
4. conclusion, always the same: the trail ends in a [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) , in the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) .

## 40.4 Exercises

**Exercise 40.1 ★.**

Define [mineral matter](#def-g6-plants-are-producers-matter) and [organic matter](#def-g6-plants-are-producers-matter), with two examples each.

**Solution of Exercise 40.1.**

[Mineral matter](#def-g6-plants-are-producers-matter): matter of the non-living world — water, rock (also air’s gases, [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs)). [Organic matter](#def-g6-plants-are-producers-matter): matter made by [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) and composing their bodies — wood, [muscle](https://one-course.com/books/biology/1/en/chapter/17-bones-and-muscles#def-g3-bones-and-muscles-muscle) (also sugar, wool, fat).

**Exercise 40.2 ★.**

State the [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)’ trade: inputs, [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) source, output, and the workshop where it happens.

**Solution of Exercise 40.2.**

Inputs: water and [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) from the soil, a gas (carbon dioxide) from the air. [Energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs): [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), caught by the green substance. Output: [organic matter](#def-g6-plants-are-producers-matter) — sugar, then wood, [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), [root](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed). Workshop: the green [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), by day.

**Exercise 40.3 ★.**

Sort as mineral or organic: dew, a snail [shell](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-covering), beeswax, granite, cooking oil, sea salt.

**Solution of Exercise 40.3.**

Mineral: dew, granite, sea salt. Organic: beeswax, cooking oil — and the snail [shell](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-covering) is the snail’s making, built of mineral substance the [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) laid down: made by a [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components), from mineral supplies. (Credit for either answer with that reasoning.)

**Exercise 40.4 ★.**

Where did the oak’s kilograms mostly come from, if hardly from the soil?

**Solution of Exercise 40.4.**

Mostly from air and water — the gas taken from the air and the water drunk by the [roots](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) — assembled in the [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) with [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions)’s [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs); the soil gave only small amounts of [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs).

**Exercise 40.5 ★.**

Which gas does the working [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) take from the air, and which does it release? Who exhales the first and needs the second?

**Solution of Exercise 40.5.**

It takes carbon dioxide and releases oxygen. Every [breathing](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements) [living thing](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) exhales the first and needs the second — ourselves included.

**Exercise 40.6 ★.**

Name four [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) storage organs and what each stores, from [Example 40.7](#ex-g6-plants-are-producers-pantry).

**Solution of Exercise 40.6.**

The potato [tuber](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber) and the tulip [bulb](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber) (underground stores), the bean’s thick halves (the [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed)’s [food store](https://one-course.com/books/biology/1/en/chapter/20-animals-through-the-seasons#def-g3-animals-through-seasons-active)), the carrot’s fat [root](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), the sugar-filled beet — all organic reserves banked from summer’s manufacture.

**Exercise 40.7 ★★.**

Why does the dark-cupboard [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) starve with a full larder of [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs)? Which input has no substitute?

**Solution of Exercise 40.7.**

Because the manufacture runs on [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions): with no [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) there is no [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs) to build [organic matter](#def-g6-plants-are-producers-matter), whatever minerals wait in the soil. [Light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) is the one input with no substitute — the salts are seasoning, not fuel.

**Exercise 40.8 ★★.**

Why can no [animal](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) be the first link of a [food chain](https://one-course.com/books/biology/1/en/chapter/19-food-chains#def-g3-food-chains-chain)? Answer with the [producer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles)/[consumer](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) distinction.

**Solution of Exercise 40.8.**

Because a chain’s first link must put new [organic matter](#def-g6-plants-are-producers-matter) into the living world, and [animals](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-animal) are [consumers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles): they can only transform [organic matter](#def-g6-plants-are-producers-matter) already made by someone else. Only [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) manufacture it from mineral supplies — so the first link is always green.

**Exercise 40.9 ★★.**

Run [Method 40.8](#met-g6-plants-are-producers-trace) on a cheese sandwich: bread, butter, cheese — three trails to three [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts).

**Solution of Exercise 40.9.**

Bread: wheat — the wheat [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s [seeds](https://one-course.com/books/biology/1/en/chapter/16-flowers-fruits-and-seeds#prop-g3-flowers-fruits-seeds-transform); trail ends in the wheat [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts). Butter: cream — [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) — the cow — grass; trail ends in the grass [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts). Cheese: [milk](https://one-course.com/books/biology/1/en/chapter/8-how-animals-grow-up#def-g2-animals-grow-up-born) — the cow — grass again. Three foods, three (or two) [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts), all in the [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions).

**Exercise 40.10 ★★.**

“Compost feeds the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) the way hay feeds a cow.” Correct the sentence precisely, using [Remark 22.5](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#rem-g4-what-plants-need-soil) and this chapter’s definitions — what does compost actually supply, and what does the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) make for itself?

**Solution of Exercise 40.10.**

Hay is the cow’s food — [organic matter](#def-g6-plants-are-producers-matter) she transforms into her body. Compost is not the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s food: it restocks the soil’s *mineral* salts as it rots. The [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) then makes its own [organic matter](#def-g6-plants-are-producers-matter) from those minerals, air, water and [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions). The cow eats meals; the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) manufactures them.

**Exercise 40.11 ★★.**

A sealed, lit aquarium of water [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) and [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups) can run for months; a sealed *dark* one fails in days. Use [Remark 40.5](#rem-g6-plants-are-producers-gas) to explain both outcomes.

**Solution of Exercise 40.11.**

Lit, the [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’ daytime manufacture releases oxygen and takes up carbon dioxide, balancing the [fish](https://one-course.com/books/biology/1/en/chapter/14-sorting-living-things#prop-g3-sorting-living-things-groups)’s [breathing](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements) — the gas swap runs both ways and the jar cycles. Dark, the manufacture stops while every inhabitant ([plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) included) keeps [breathing](https://one-course.com/books/biology/1/en/chapter/26-breathing#def-g4-breathing-movements): oxygen runs out, carbon dioxide piles up, and the sealed world suffocates.

**Exercise 40.12 ★★★.**

An old experiment: a willow sapling grown five years in a tub gained many kilograms; the tub’s dried soil lost only grams. The experimenter concluded “the tree was made of water alone.” Which part of his conclusion was right, which incomplete — and what second mineral input, unknown to him, would a modern biologist add?

**Solution of Exercise 40.12.**

Right: the tree’s matter did not come from the soil — his weighing proved that forever. Incomplete: water was only one bulk ingredient; he could not know about the gas taken from the air, which supplies much of the wood’s substance. The modern addition: carbon dioxide from the air (plus the soil’s small [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs)) — water and air together, assembled by [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions).

## 40.5 Problem: The Market Gardener’s Year

**Problem 40.1.**

Weekend problem — light, leaves and the ledger of a vegetable garden

A market gardener grows potatoes, carrots, beans and lettuces, and keeps a sharp ledger of what goes in and what comes out.

**Part I — The ledger’s riddle.**

1. The garden yields two tonnes of vegetables a year; the gardener spreads only sacks of compost. Weigh the riddle: where do the tonnes come from, if not from the sacks? (Answer with the [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) ’ trade.)
2. Classify the yield: the potato, the carrot, the bean [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) , the lettuce [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) — name each one’s role for the [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) (storage organ, working organ, [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed) store).
3. The gardener says: “my real supplier delivers by daylight.” Translate into [Proposition 40.3](#prop-g6-plants-are-producers-produce) ’s terms.
4. Why does the gardener still need the compost at all, if not for the tonnes? (Recall the mint in sand.)

**Part II — Reading the seasons.**

5. June’s lettuces, shaded under a trial cloth for a week, come out pale and stretched. Name the experiment this repeats, and the input it removed.
6. The potato rows are earthed up and their lush tops praised: “good tops, good [tubers](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber) .” Explain the saying — what is the connection between working [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) above and swelling storage below?
7. August’s drought halts growth though the sun blazes. Which mineral input has failed, and why can [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) not substitute for it?
8. In September the gardener cuts and removes the bean [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) but digs their [roots](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) in. A neighbor calls this waste. Defend the practice with the matter definitions — what is being returned to the soil, for whom?

**Part III — Beyond the garden.**

9. The gardener’s pig eats the small potatoes; the family eats the pig. Write the chain, and state where its [organic matter](#def-g6-plants-are-producers-matter) was originally manufactured.
10. A customer claims her salad is “sun, mostly”. Audit the claim: list the salad [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) ’s actual ingredients and the sun’s exact role.
11. Frost kills the last lettuces overnight; they rot where they lie by November. Their [organic matter](#def-g6-plants-are-producers-matter) does not vanish. Anticipate [Chapter 42](https://one-course.com/books/biology/1/en/chapter/42-decomposers-and-the-soil#ch-g6-decomposers-and-soil) : who takes it, and toward what state?
12. Summarize the garden in one sentence containing: [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) , [mineral matter](#def-g6-plants-are-producers-matter) , [organic matter](#def-g6-plants-are-producers-matter) , [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) .

**Solution of Problem 40.1.**

**1.** The tonnes are [organic matter](#def-g6-plants-are-producers-matter) manufactured by the [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) themselves from mineral supplies — water, the air’s carbon dioxide, the soil’s salts — with [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) as the [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs). The sacks restock minerals; the air and rain deliver the bulk; the [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) do the making.

**2.** Potato: underground storage organ ([tuber](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber)). Carrot: storage [root](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts). Bean [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed): the [seed](https://one-course.com/books/biology/1/en/chapter/9-from-seed-to-plant#def-g2-from-seed-to-plant-seed)’s [food store](https://one-course.com/books/biology/1/en/chapter/20-animals-through-the-seasons#def-g3-animals-through-seasons-active), packed for the next [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant). Lettuce [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts): the working organ itself — the light-catching workshop, eaten fresh.

**3.** The true supplier is [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions): every gram of yield was built with [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions)’s [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs), by day, in the [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts).

**4.** For the [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs): harvests carry them off, and without restocking the [plants](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) would run mineral-short like the mint in sand — small in bulk, indispensable in function.

**5.** The dark-cupboard experiment (the pale prisoner): the cloth removed [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions), and a week of it already shows — pale, stretched, weak manufacture.

**6.** The [tubers](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber) are filled by the tops: [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) manufacture sugar by day, and the surplus is piped down and banked in the swelling [tubers](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber). Lush working [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) mean a big surplus — good tops, good [tubers](https://one-course.com/books/biology/1/en/chapter/24-plants-without-seeds#ex-g4-plants-without-seeds-bulbtuber).

**7.** Water. Manufacture needs all its inputs at once: [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) supplies [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs), not substance — with the [roots](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) dry, there is nothing to build with, however bright the sky.

**8.** The dug-in [roots](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) are [organic matter](#def-g6-plants-are-producers-matter) returned to the soil: rotting, they will free their minerals for coming crops — the return rule of [Proposition 35.5](https://one-course.com/books/biology/1/en/chapter/35-people-and-nature#prop-g5-people-and-nature-lasting), paid in [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) matter. The waste would be burning them.

**9.** Potato [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant) $\rightarrow$ pig $\rightarrow$ the family. All its [organic matter](#def-g6-plants-are-producers-matter) was first manufactured in the potato [plant](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-plant)’s [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) — the pig and the family only transformed it.

**10.** Ingredients: water and [mineral salts](https://one-course.com/books/biology/1/en/chapter/22-what-plants-need#prop-g4-what-plants-need-needs) from the soil, carbon dioxide from the air — assembled into [leaf](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) matter. The sun’s exact role: [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs), not substance. Her salad is water, air and earth, *built by* sunlight — poetic credit deserved, ingredient list wrong.

**11.** The [decomposers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) — soil life from worms and woodlice down to [living things](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-components) too small to see — feed on the dead [leaves](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) and break their [organic matter](#def-g6-plants-are-producers-matter) down toward [mineral matter](#def-g6-plants-are-producers-matter) again, restocking the soil the next crops will draw on.

**12.** For example: “The garden’s [producers](https://one-course.com/books/biology/1/en/chapter/34-food-webs#def-g5-food-webs-roles) build [organic matter](#def-g6-plants-are-producers-matter) — the harvest — out of [mineral matter](#def-g6-plants-are-producers-matter) from soil, water and air, using [light](https://one-course.com/books/biology/1/en/chapter/37-exploring-our-environment#def-g6-exploring-our-environment-conditions) as their [energy](https://one-course.com/books/biology/1/en/chapter/18-a-balanced-diet#prop-g3-balanced-diet-jobs).”