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plants that produce seeds

Seed-bearing plants

Plants are living:

  • They grow and die.
  • They produce new individuals.
  • They are made of cells.
  • They need energy, nutrients, air and water.
  • They respond to their environment.

Plants are different to animals partly because they use the energy from sunlight through a process called photosynthesis (although there are a few plants that don’t). Plant cells have much in common with animal cells, but they have some different structures.

There are many different kinds of plants. Just take a walk in the garden or bush to see the amazing variety. Botanists organise the plant kingdom into groups based on features found in different plants.

Plants are divided into two big groups, based on how they reproduce:

  • Plants that produce seeds (flowering plants and cone plants).
  • Plants that produce spores (ferns, mosses, liverworts and green algae).

Seed plants have special structures on them (flowers or cones) where special male and female cells join through a process called fertilisation. After fertilisation, a tiny plant called an embryo is formed inside a seed. The seed protects the embryo and stores food for it. The seed is dispersed away from the parent plant, and when conditions are right, the embryo germinates and grows into a new plant.

There are two main groups of seed plants:

  • Gymnosperms – plants with cones.
  • Angiosperms – plants with flowers.

Gymnosperms

These seed plants do not have flowers or fruit – their seeds are held in cones. Next time you pick up a pine cone, look for loose seeds inside. Male cones make pollen, which is carried to female cones by the wind. After the female gametes are fertilised by male gametes from the pollen, the female cones produce seeds. These are then scattered away from the plant by wind or animals.

Most gymnosperms are trees. There are about 20 native gymnosperms in New Zealand, including our tallest tree, the kahikatea (Dacrycarpus dacrydioides, white pine). Others include mataī (Prumnopitys taxifolia, black pine), tōtara (Podocarpus totara), rimu (Dacrydium cupressinum, red pine) and kauri (Agathis australis). The main tree that makes up New Zealand’s plantation forests is the exotic gymnosperm Pinus radiata.

Angiosperms

Angiosperms produce flowers, which are special structures for reproduction. They contain male parts that make pollen and female parts that contain ovules. Some plants have these male and female parts in different flowers. Pollen is carried from a male part to a female part by wind or animals (a process called pollination), where it releases male gametes that fertilise the female gametes in the ovules. The ovules develop into seeds, from which new plants will grow. In most angiosperms , part of the flower develops into fruit, which protects the seeds inside them. Fruit can be soft like oranges or hard like nuts.

Flowering plants form the biggest group of seed plants, with about 300,000 species around the world – that’s 90% of the whole plant kingdom. New Zealand has about 2,000 native angiosperms , and an amazing 25,000 introduced species found mainly in gardens, farms and orchards.

Flowering plants are all around us, even if sometimes we don’t recognise them as having flowers. We all know the showy flowers of native kōwhai, flax and pōhutakawa and all those lovely coloured flowers in our gardens, but the tall toetoe and the grasses in our lawns are also flowering plants.

Plants are living:

Saving Seed: Will the seed produce plants similar to the plant it was collected from?

Rhoda Burrows

Professor & SDSU Extension Horticulture Specialist

It can be very rewarding to harvest and save seed of ornamental and vegetable plants. But why is it that sometimes when we plant the seed we saved, the results do not seem to be very like the plant we collected the seed from?

To answer that question, it helps to know a little more about both the plant we collected the seed from, as well as the likely source of the pollen that fertilized the flower to form the seed.

Seed Sources

When a seed is formed by a plant, it is the result of pollen fertilizing an egg (ovule). Whether the resulting seed “comes true,” that is, produces plants identical to the plant that it was harvested from, depends on whether it is outcrossed, inbred, or hybrid. These three options determine whether the two sets of genes (one from the pollen and one from the ovule) are likely to be identical or very different.

+ Inbred

In inbred plants, the eggs are fertilized with pollen from the same plant. (Another term for this that you may have heard is self-pollination). The progeny will each have two identical (or nearly so) sets of genes, exact copies of their parents, and very similar to each other. Most peas and beans are inbred. Since seed from self-pollinated plants will produce plants very like the plant it was produced on, these kinds of plants are ideal for seed saving.

✗ Outcrossed

Outcrossed plants require pollen from a different plant to fertilize the egg (also called cross-pollination). Some outcrossing species have the female and male parts in separate flowers (corn or squash) or even separate plants (asparagus). Others have both parts in the same flower, but the egg will accept pollen only from another flower or plant. Apples are an example of this – that is why a separate pollinator tree is needed to obtain fruit. The two sets of genes in the offspring of outcrossed plants tend to have a lot of variation, so that the outcome of crossing is less predictable, somewhat like the variation between siblings in a human family. Seed from outcrossed plants will not necessarily come true; thus you should not save seed from these plants if you want to be certain that the plants will be exactly the same as their parents. However, if you have grown only one variety (and your neighbors have grown the same variety or are far enough away to avoid wind- or insect- cross pollination), you can still expect fairly consistent results from that seed.

✗ Hybrids

Hybrids result from crossing two different inbred lines. All of the first generation of plants from this cross will contain the exact same two sets of genes (one from each line) and thus will be identical to each other. This first generation is what you buy in a seed packet marked “Hybrid” or “F1”. However, the next generation (the plants that will grow from seed produced from plants grown from “F1” seed) will contain a random mixture of genes, resulting in plants that may have a whole range of desirable and undesirable characteristics. Thus you should not save seed from F1 or hybrid plants if you want to be certain that the plants grown from that seed will be the same as their parents.

Plant Types

How can you tell whether a plant is outcrossed, inbred, or hybrid? First of all, look for the words “hybrid” or “F1” on seed packets. Any plant that has separate male and female flowers is most likely outbred. Plants with closed flowers, such as peas and beans, are usually inbred. Sometimes it will not be obvious whether the plant is inbred or outbred. Following is a list of plants that either mostly outcrossed or inbred.

It can be very rewarding to harvest and save seed of ornamental and vegetable plants. But why is it that sometimes when we plant the seed we saved, the results do not seem to be very like the plant we collected the seed from?