Category Plants & Animals

Trees produce seeds just as smaller plants do. Their flowers or cones are fertilized by the wind, or insects or birds. But a parent tree takes up large amounts of water from the area around it, and its leaves prevent sunlight from reaching the ground beneath, so it is important that all the seeds do not fall directly beneath the tree. Some trees produce fruits that are eaten by birds or animals and carried far away in their digestive systems. Others bear seeds that have “wings” and can be blown far away by the wind.

Wind pollinator flowers may be small, no petals, and no special colors, odors, or nectar. These plants produce enormous numbers of small pollen grains. For this reason, wind-pollinated plants may be allergens, but seldom are animal-pollinated plants allergenic. Their stigmas may be large and feathery to catch the pollen grains. Insects may visit them to collect pollen, but usually are ineffective pollinators and exert little natural selection on the flowers. Anemophilous, or wind pollinated flowers, are usually small and inconspicuous, and do not possess a scent or produce nectar. The anthers may produce a large number of pollen grains, while the stamens are generally long and protrude out of flower. There are also examples of ambophilous (pollinated by two different classes of pollinators) flowers which are both wind and insect pollinated.

Most conifers and about 12% of the world’s flowering plants are wind-pollinated. Wind pollinated plants include grasses and their cultivated cousins, the cereal crops, many trees, the infamous allergenic ragweeds, and others. All release billions of pollen grains into the air so that a lucky few will hit their targets.

Water pollinated plants are aquatic. Pollen floats on the water’s surface drifting until it contacts flowers. This is called surface hydrophily, but is relatively rare (only 2% of pollination is hydrophily). This water-aided pollination occurs in waterweeds and pondweeds. In a very few cases, pollen travels underwater. Most aquatic plants are insect-pollinated, with flowers that emerge from the water into the air. 

Trees can be divided into two groups. Broad-leaved trees, which may also be deciduous, meaning that they drop their leaves in winter, are flowering plants. Sometimes their flowers are very small and difficult to spot. Conifers, most of which are evergreen, retaining their leaves all year round, are cone-bearers. They have small male cones and larger female cones instead of flowers.

If trees didn’t have flowers there would be no seeds, and if there were no seeds, new trees wouldn’t come up each year. And if new trees didn’t come up each year, there wouldn’t be forests.

Every single tree in the world has flowers, though sometimes they are too small to be seen or are buried so deep in the leaves that nobody can find them. Certain trees have flowers that come before their leaves, so people don’t notice the tiny blooms, which usually are not very colorful.

Certain trees have flowers that have no petals; others are green and appear to be buds of coming leaves unless you look very closely. There are even trees whose flowers are too small to see without a microscope.

Evergreen: Evergreen any plant that retains its leaves through the year and into the following growing season. Many tropical species of broad-leaved flowering plants are evergreen, but in cold-temperate and Arctic areas the evergreens commonly are cone-bearing shrubs or trees (conifers), such as pines and firs. The leaves of evergreens usually are thicker and more leathery than those of deciduous trees (those that shed their leaves in autumn or in the tropical dry season) and often are needlelike or scalelike in cone-bearing trees. A leaf may remain on an evergreen tree for two years or longer and may fall during any season. An evergreen forest may be needle-leaved, as the coniferous forests of the Northern Hemisphere, or broad-leaved, as the temperate rain forests of the Southern Hemisphere and the broad sclerophyll forests (with thickened, hardened foliage resistant to water loss) of coastal areas of the Northern Hemisphere. Most tropical rain forests contain broad-leaved evergreens.

As well as directly affecting the environment, trees supply homes and food for millions of other living creatures, including people. They are also the source of wood, which is used in buildings and for making such essential items as furniture and paper.

Trees are very important, valuable and necessary to our existence as they have furnished us with two important life essentials; food and oxygen. Apart from basically keeping us alive, there are many other little and big benefits we get from trees. So, trees are vital resources for the survival of all living beings. Therefore, Governments world over and many Organizations are taking steps to prevent deforestation and to tell the benefits of planting trees. Let us go through some important points about the Importance of trees for the existence of human life.

Trees play an especially important role in enhancing our quality of life in the urban environment and this is acknowledged in the Governments Sustainable Development Strategy. They screen unsightly structures and activities, give privacy and soften the hard lines of buildings. Trees also bring colour and contrasts into the urban environment.

Not only do trees have a visual quality, but they also enhance the environment in less obvious ways. Trees improve air quality by acting as natural air filters removing dust, smoke and fumes from the atmosphere by trapping them on their leaves, branches and trunks. Just 1 hectare of beech woodland can extract 4 tonnes of dust per year from the atmosphere. Trees reduce the ‘Greenhouse’ effect by removing carbon dioxide from the air and releasing oxygen. Each year a mature tree produces enough oxygen for 10 people.

Trees are also an effective sound barrier and can limit noise pollution. Recent research shows that trees also help reduce the stress of modern life. Trees in themselves benefit the environment and the landscape, but they are also an integral part of the ecosystem providing benefits to wildlife and biodiversity. Trees, especially older or veteran trees and those in groups or woodlands, provide habitats for native ground flora such as bluebells and fauna, particularly bats, red squirrels and invertebrates. The planting of trees and the care and preservation of mature trees can go a long way to making Trafford a great place to live, work learn and relax.

Trees are the largest plants on Earth and play a very important part on the planet. They cover almost a quarter of the Earth, helping to stabilize the atmosphere by taking in huge amounts of carbon dioxide from the air and giving off oxygen. In addition, tree roots help to retain fertile soil and stop the rain from washing it down hillsides, while the huge amount of water vapour given off by trees has an important effect on the weather.

The largest tree in the world is a giant sequoia (Sequoiadendron giganteum) in California’s Sequoia National Park. Called General Sherman, the tree is about 52,500 cubic feet (1,487 cubic meters) in volume.

That’s the equivalent of more than half the volume of an Olympic-size swimming pool, commonly considered to be 88,500 cubic feet (2,506 cubic meters).

General Sherman is estimated to be about 2,000 years old. That makes it only a middle-age giant sequoia, as other trees are believed to be more than 3,220 years old, based on tree ring counts.

The tree lost a huge branch in 2006, which shattered a new walkway and fence below. It didn’t affect General Sherman’s ranking as the largest tree, however, as that was calculated using trunk volume and not branches.

Flowers that are closely related often cross-pollinate in the wild, creating a variety of flower shades and shapes. Under controlled conditions, plant breeders ensure that their parent plants are not pollinated naturally. They then transfer pollen from a selected “father” plant to the stigma of the “mother” plant and wait for seeds to form. These are sown to see what kind of flowers result. It may be years before the results are known and even then only a few of the plants will prove to be different and attractive enough to be launched as new varieties.

The goal of flower breeding is the creation of new flowers that would not normally be found in nature. By selecting two flowers of the same species with different traits — such as color, height or bloom type — and cross-pollinating them, seeds that combine the traits of both plants will be produced. The seeds produced are F1 hybrids that will grow into new, different plants. Not all flowers are candidates for cross breeding, as some have natural inhibitors to prevent crossing.

Step 1

Select different varieties of the same species of parent flowers. Neither parent can be a hybrid, nor will unpredictable results occur. The parent flowers should always be the same, using the same variety to supply the ovules and the other variety to supply the pollen.

Step 2

Snip the filaments and anthers off the flower, which will supply the female parts. Hold the filament with a tweezers and cut the filament below the tweezers. Do not allow the anther to touch the center portion of the flower. Removal of the anthers ensures the flower will not self-pollinate and ruin the cross. Call this flower the female flower.

Step 3

Obtain pollen from the flower that is supplying the male parts. To store pollen, collect it from the anthers with a small camel hair brush and brush it in a vial. Label the vial with the flower species and type. Clean the brush with alcohol before using it to collect a different type of pollen. You can also gather pollen for immediate use by removing the filaments and anthers from the male flower as was done with the female flower.

Step 4

Fertilize the female flower with pollen. Dab the brush in the pollen grains in the vial and gently brush the pollen onto the emasculated female flower’s stigma. For immediate use of pollen, simply collect the anthers from the male plant and use the anthers to brush pollen onto the stigma of the female plant. Immediately cover the female flower with a cellophane bag and tie it closed with a piece of string to prevent contamination with other pollen. Tag and label the female flower as a cross with the male by listing the variety of male and female.

Step 5

Collect the seeds from the female flower once they are ripe. Usually this occurs when the flowers is wilted and dry, although readiness varies by species. Label the seeds for storage as the cross of the two varieties selected. Good record keeping is a must when experimenting with flower breeding.

Step 6

Keep notes in a notebook about the results of the breeding experiments. Add pictures of flowers and detailed descriptions of the hybrid plants created. Experiment with crossing the male of one variety with the female of another and also the reverse to see if the results are different.

When the flower has been fertilized, the ovary swells to form a fruit, inside which one or more seeds will grow. These seeds may simply fall to the ground below, or the plant may have methods of ensuring that its offspring grow much further away.

Plants make seeds that can grow into new plants, but if the seeds just fall to the ground under the parent plant, they might not get enough sun, water or nutrients from the soil. Because plants cannot walk around and take their seeds to other places, they have developed other methods to disperse (move) their seeds. The most common methods are wind, water, animals, explosion and fire.

Wind dispersal

Have you ever blown on a dandelion head and watched the seeds float away? This is wind dispersal. Seeds from plants like dandelions, swan plants and cottonwood trees are light and have feathery bristles and can be carried long distances by the wind. Some plants, like kauri and maple trees, have ‘winged’ seeds. They don’t float away but flutter to the ground. With wind dispersal, the seeds are simply blown about and land in all kinds of places. To help their chances that at least some of the seeds land in a place suitable for growth, these plants have to produce lots of seeds.

Water dispersal

Many plants have seeds that use water as a means of dispersal. The seeds float away from the parent plant. Mangrove trees live in estuaries. If a mangrove seed falls during low tide, it can begin to root in the soil. If the seeds fall in the water, they are carried away by the tide to grow somewhere else. K?whai trees also use water dispersal. They have a hard seed coat that allows them to float down streams and rivers. That is one of the reasons k?whai trees are commonly found on stream banks.

Animal dispersal

Over 70% of plants in our woody forests in New Zealand have fleshy fruit that is eaten by birds. Chemicals in our native birds’ digestive systems help to weaken the tough coats around these seeds. Birds often fly far away from the parent plant and disperse the seeds in their droppings. The kerer?, t?? and bellbird play an important role in seed dispersal. Trees that produce the largest fruit – miro, p?riri, tawa and taraire – rely on the kerer? because it has such a large, wide beak to eat the fruit.

Some seeds have hooks or barbs that catch onto an animal’s fur, feathers or skin. Plants like pittosporum have sticky seeds that can be carried away by birds. Humans can also spread seeds if they get stuck to our clothing or shoes – and if we throw fruit pips and stones out of the car window!

Fire

Plants cannot run away from a fire so some plants have developed a way to help their seeds survive. There are some species of pine tree that require the heat from a fire before their cones will open and release seeds. Banksias, eucalypts and other Australian plants also rely on fire. The intensity and timing of the fire is important. It needs to be hot enough to trigger the cones to open, but if fires are too frequent, there is not enough time for the plants to grow big enough to make new seeds.

Adaptation and seed dispersal

Adaptation is an evolutionary process that helps an organism makes the most of its habitat. Seed dispersal is an example of adaptation. Fires are common in Australia, so some plants have adapted and become well suited to make the most of it. Mangrove trees have seeds that float, making the most of their watery environment.