Photosynthesis in a flowering plant The second largest kingdom of living things after animals is the plants. The key feature of a plant which sets it apart from other living things is that it obtains energy by the process of photosynthesis. All plants take in sunlight and carbon dioxide from the air which they combine with water to make sugars, their food. A plant is made up of millions of microscopic cells, in which thousands of chemical changes take place as part of the plant’s life processes. Like an animal’s body, a typical plant has many specialized parts for different jobs. The roots take in water, minerals, salts and other vital nutrients from the soil in which the plant grows. The stiff stem holds the main parts of the plant above the ground so that the leaves can catch the maximum amount of sunlight. Plants are divided into two main kinds: the simpler types without flowers, and those with flowers. The study of plants is called botany.
Mosses and liverworts
Mosses and liverworts are types of non-flowering plants called bryophytes. They reproduce by making tiny, dust-like spores which grow into new plants. A moss has small green leaflets but no proper stem or roots. It absorbs water and nutrients through its leaflets so it can only live in damp places. Liverworts grow in similar places. Each has a low, flattened body known as a thallus.
Liverwort Mosses and liverworts, along with the algae, are called non-vascular plants: they lack roots and stems, and so have no tube-like vessels inside them to transport water and nutrients around the plant. All other plants are known as vascular plants.
Ferns, or pteridophytes, are another kind of non-flowering plant. Like the bryophytes, they reproduce by making spores, but unlike them, they have roots which absorb water and minerals from the soil, and a stiff stem to hold up their much-branched fronds. Ferns can survive on low levels of light. Many types grow in woodlands in the shade under large trees.
Gymnosperms are seed-producing non-flowering plants. They include conifers, cycads, gnetophytes (a group of woody plants) and the ginkgo. The name "gymnosperm" comes from the Greek gymnospermos which means "naked seeds". Unlike flowering plants, in which the seeds are enclosed inside ovaries, gymnosperm seeds develop on the surface of scales or leaves or cones.
Conifers are much the largest type of gymnosperms. Conifer seeds on the faces of each of the scales that make up the cones. Pines, firs, spruces, larches, redwoods and cypresses are all conifers.
The flowers of flowering plants, also known as angiosperms, are body parts specialized for breeding. They contain male and female parts, which they use to reproduce and make seeds. In suitable conditions these grow into new plants.
Flowering plants are by far the main or dominant group of plants around the world, except for the conifer forests in colder regions. Flowering plants include familiar herbs, grasses, reeds, rushes, wild and garden flowers, and most trees and bushes (except for the conifers). There are some 260,000 different kinds or species of flowering plant compared to about 550 species of conifer, 11,000 ferns and 14,000 mosses and liverworts.
Monocots and dicots
The two main kinds of flowering plants are named from the number of cotyledons they have. These are the nutrient-packed “seed leaves” that provide food for the baby plant as it grows from a seed. Monocots have one cotyledon and include palm trees, grasses and some flowers such as lilies, crocuses and orchids. Dicots have two cotyledons and include all other kinds of flowers, bushes and trees.
Some plants feed on animals. The Venus fly-trap lives in poor soil with few minerals and nutrients. It catches small animals, dissolves them and takes in their juices as an extra nutrient supply. The spiny-edged leaf of a Venus fly-trap snaps shut whenever a small insect lands on it. The spines interlock to trap the struggling insect.
Like the Venus fly-trap, the pitcher plant grows in nutrient-poor soil. Insects attracted to the plant’s nectar fall into bottle-shaped pitchers filled with rainwater and the plant’s digestive juices, where they drown. The plant soaks up nutrients from the dead and digested insects.
Consultant: Chris Jarvis