Pollination takes place. Pollen drifts on the wind to the little female cone, where it rests on sticky fluid near the scale's tip. The scale tip expands slightly to allow pollen to enter the cone. The pollen remains for a year. In the next season, when the tree is in bloom, any seeds that fall onto the ground will be covered with more sticky fluid that will help them be carried away from the parent tree.
When trees like pistacios and silkwoods produce male and female flowers on the same plant, biologists assume that insects are responsible for moving the pollen from one flower to the other. Some insect species are capable of doing this; others not so much. Cones are edible and contain pulp and oil inside their hard shells. They provide shelter for birds and offer nesting sites for various animals.
Female cones tend to be larger than male cones. This is because they contain many more seeds. Each seed is attached to a thread called a pedicel. When all the seeds have been released, the pedicels break off leaving the empty cone behind. Male cones do not have seeds inside them but they still need to be pollinated in order to set fruit. Insects visit male cones looking for females to fertilize. They do this by rubbing their bodies against the cone's branches or trunk. Some insects can even climb trees using their mouthparts instead of their feet!
The pollen next develops into a pollen tube, which develops into the female megasporangium, commonly known as an ovule. The procedure might take up to a year. When the pollen grain germinates, it forms a radicle that penetrates the ovular wall and enters the ovary. There it grows into a plant cell and sends out new roots that grow into another tree. The tree dies after reproduction has been completed.
Seed cones are similar to fruit in appearance. They contain an ovary with two chambers: one large central chamber and a smaller upper chamber. The seed is surrounded by a shell called the pericarp. Like other cones, seed cones are modified leaves. During flower development, the stamens (male parts of the flower) become attached to the pericarp. As the seed matures, the pericarp thickens and colors from green to red or brown. It may be covered with hair when mature. Pollen grains are released into the air where they can reach other plants by wind or insect pollination. Cones are produced only during flowering for successful dispersal of seeds. After seed production, cones fall off the mother tree although some species retain their seed cones through winter. Seedlings develop from the underground stem called a rhizome.
Conifer trees are famous for their cones.
Cells in each are steadily developing to generate male gametes, known as sperm, and female gametes, known as eggs, which will combine to form the seeds. When pollen from another species arrives, it brings with it genes for creating hybrid plants. Seeds from such a plant would be genetically different because they would have both sperm from one species and egg from another.
When flowers produce fruit (seeds) containing ovules (female organs that develop into embryos) instead of pollen, this is called "apophyllous" or "pollenless". Most conifers are apophyllous, as are many cycads and ginkgos. In these cases, the pollen is carried by insects like bees or wasps who visit the flower for its sweet scent rather than for its reproductive material.
Some plants produce both pollen and ovules in equal amounts. These are called "bisexual" plants. Most flowering plants are bisexual; they can fertilize themselves and produce seeds that carry their genetic information all at once (a mass generation), or they can take years to grow before producing more flowers that do the same.
The term "pollinated" means having your genes passed on to future generations due to pollen being transferred to the stigma of a flower.
Once fertilization has taken place, the cells of the ovule divide rapidly, forming a multilayer embryo within the seed coat.
Inside the pollen grain is half of the sperm cell that will unite with an egg from the other pistil to form a new plant. The remaining half of the sperm cell is lost after pollen germination. Pollen provides nutrients for the developing embryo through photosynthesis, using carbon dioxide from the air and water from the stomata. As the pollen matures it loses its water content and becomes dry so it can be carried by the wind to another plant for fertilization.
During flowering, a pine tree will produce cones of pollen and ovules. When bees visit the flowers they carry away both types of pollen, which can grow into two different plants after being deposited in the right environment. Some pollen may also fall onto the ground or onto other plants, which could cause problems for those plants if they contain genes that are the same as those in the pollen that was dropped. For example, farmers keep trees like pistachios and almonds free of pests by spraying them with honeybees before harvest to give protection against any harmful insects that might be around.
Male pinecones generate pollen, which is a powdery substance. Male pinecones produce pollen, which is blown throughout the air by the wind and, ideally, to another female pinecone on a different pine tree. Pollination occurs when pollen from a male pinecone reaches a female pinecone. If there is no female pinecone available nearby, the pollen will land on something else: an animal's fur or some other plant. This is called out-crossing.
Female pine cones contain eggs. When pollen lands on an egg it can become fertilized. The seed inside a female cone will eventually fall to the ground or be picked up by some animal. This is called ovule dispersal. Some species of pine trees have both male and female cones on one tree. In these cases, pollen must be transported between cones to result in fruit set. Pine trees usually rely on insects for pollination because cones are protected by spines that not even insects can get into. However, some species of pine trees have evolved to use self-pollination because insects carry pollen too far from the parent tree.
Some plants use more than one method of reproduction. For example, some roses have both male and female flowers on the same plant. The location of each flower type on the rose determines how it will reproduce. If the male flowers are at the end of long stalks called racemes, they will pollinate many female flowers over time.
Lobdell claims that conifers rely on the wind to reproduce. Short-lived male cones generate pollen in the spring, which is transported by the breeze to female cones. Male cones often develop toward the bottom of the tree and female cones near the top, reducing the likelihood that a single tree would pollinate itself. As a result, most conifers are genetically distinct from their neighbors. Lobdell also notes that some species of pine produce cones that fall off the tree early in the season, providing more opportunities for germination.
Conifer seeds have thick coats that protect them while they're on the cone and when planted will usually root within two years. It takes several decades before a conifer seed produces a new tree. However, through human intervention (such as clear-cutting) many species are now endangered with extinction.
Seedlings lack special defenses against predators so need to be camouflaged to avoid being eaten. Thus, young pines grow long branches and leaves to hide themselves from predators. When they grow larger they start producing cones of their own to continue reproducing.
As you can see, there are many reasons why pinecones are located at the top of trees. If you were to visit a forest full of pine trees, you would likely find a majority of the cones at the top of their trees.