Cross Pollination And Its Importance

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Pollination is the sexual reproduction method in all plants by transferring the grains of pollen from the anther to the gynoecium’s stigma. There are two types of pollination. They are self and cross-pollination.

The transfer of the pollen grain from the flower of one plant to the flower of a plant is called cross-pollination. In this natural method, the pollen is transferred from an anther of a flower of one plant to a stigma of another. Both plants are of the same species. When pollen grains move from an anther to the flower’s stigma on another plant, this pollination is called self pollination.

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Here we cover the importance of cross-pollination and its advantages and disadvantages.

Difference Between Self Pollination and Cross Pollination

There are some fundamental differences between self-pollination and cross-pollination. Pollination isn’t necessary to make flowers grow and bloom, but it is necessary for many plants to grow fruit. They take pollen from one plant to another, thereby making plant reproduction possible.

Self-pollination is the transfer of pollen grains from anthers to the stigma of a flower, and this process takes place between the flowers of the same plant. On the other hand, cross-pollination is the transfer of pollen grains between the flowers of the different plants of the same species.

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Self-pollination involves a single plant, whereas cross-pollination involves two different plants of the same species. Self-pollination occurs in perfect flowers only, whereas cross-pollination occurs in imperfect and perfect flowers.

In self-pollination, pollinating agents are not needed. On the other hand, a pollinating agent, like wind, insects, water, etc., is necessary for cross-pollination. Self-pollination transfers a limited amount of pollen, whereas cross-pollination transfers large numbers of pollen.

Advantages of Cross Pollination

  • Cross-pollination produces healthier individuals.
  • It has seeds in great numbers, which are very beneficial.
  • The varieties grown by cross-pollination show traits of the same or many different species.

Disadvantages of Cross Pollination

  • There is a pollinating agent always required to carry out cross-pollination. The agent may not be available at a proper time.
  • Many pollen grains are produced to attain the goal of cross-pollination. Thus there is a substantial wastage of pollen grains.
  • The plant wastes energy to produce nectar, fragrance, and large colored petals.
  • Pollen grains are being wasted in more significant quantities.
  • Because of the distance barrier, pollination may fail.
  • Cross-pollination has the potential to introduce undesirable traits.
  • It is uneconomical for plants to create massive, scented, nectar-filled flowers to attract insects.

Advantages of Cross Pollination over Self Pollination

Cross-pollination has been defined as the pollination between the flowers of the same species on two different plants.

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Unlike self-pollination, cross-pollination involves mixing the characteristics of two parents. This mixing results in a greater variety of individuals produced.

Plants with Self-pollination and Cross Pollination

Plants such as wheat, rice, peas, orchids, barley, tomatoes, peaches, and apricot undergo self-pollination. On the other hand, plants such as mulberry, maize, pumpkins, strawberries, blackberries, plums, grapes, daffodils, maple, catkins, and grasses go through cross-pollination.

Importance of Cross Pollination

The essential staple food crops on the planet, like wheat, maize, rice, soybeans, and sorghum, are wind pollinated or self-pollinating. When you consider the top 15 crops that contributed to the human diet globally in 2013, research studies found that slightly over 10% of the total human diet of plant crops is dependent upon insect pollination. This amounts to approximately 211 out of 1916 kcal/person/day.

Pollination management is an upcoming branch of agriculture that seeks to protect and enhance present pollinators. It involves the culture and addition of pollinators in monocultural situations, for example, in commercial fruit orchards.

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California almond orchards have the largest managed pollination event in the world. In these California almond orchards, nearly half (about one million hives) of the US honey bees are brought over each spring. Similarly, New York’s apple crop requires about 30,000 hives. The blueberry crop in Maine uses about 50,000 hives each year.

So far, the US solution to the pollinator shortage has been for commercial beekeepers to become pollination contractors and migrate away. Just as the harvesters follow the wheat harvest from Manitoba in Canada to Texas in the USA, the beekeepers follow the bloom from south to north to provide pollination for several crops.

Cross Pollination and Agriculture

Bees are placed in commercial plantations of cucumbers, melons, strawberries, squash, and several other crops. Honey bees are not the only managed pollinators. A few different species of bees are also raised as pollinators. The alfalfa leafcutter bee is an essential pollinator for alfalfa seed in Canada and the western United States. Bumblebees are increasingly raised and used extensively for greenhouse tomatoes and several other crops.

The economic and ecological importance of natural pollination by insects to crops, improving their quantity and quality, has increasingly appreciated and given rise to new economic opportunities. Consequently, the vicinity of wild grasslands or forests with native pollinators near crops, such as almonds, apples, or coffee, can improve their yield by twenty percent.

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The benefits of native pollinators have resulted in forest owners demanding payment for their contribution to the improved crop results. This is an excellent example of the economic value of ecological services. Farmers can also raise native crops to promote native bee pollinator species, as shown by the native sweat bees in Delaware and southwest Virginia.

The American Institute of Biological Sciences has reported that native insect pollination saved an estimated $3.1 billion annually through natural crop production. Pollination produces approximately $40 billions of products annually in the United States alone.

Use of Pollinators for Cross Pollination in Agriculture

Pollination of food crops has become an environmental issue due to two trends. The monoculture trend means the requirement of greater pollinator concentrations at bloom time. However, the area is poor in terms of forage or even deadly to bees for the rest of the season.

Another trend is the decline of pollinator populations due to pesticide misuse and overuse, new diseases and parasites of bees, clear cut logging, a drop in beekeeping, suburban development, removal of hedges and other habitats from farms, and public concern about bees. Widespread aerial spraying for mosquitoes due to West Nile fears is causing an acceleration of the loss of pollinators.

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In some situations, farmers or horticulturists may aim to restrict natural pollination to only permit breeding with the preferred individual plants. You may achieve this through the use of pollination bags.

Cross Pollination by Pollinators

Hummingbirds visit and pollinate plants with tubular yellow, red, or orange flowers. They thrust their long slender bills deep into the flowers for nectar, withdrawing heads dusted with pollen. 

Moths & Bats After dark, moths and bats take over the night shift, visiting nocturnal blooms heavy with fragrance and large amounts of dilute nectar. 

Butterflies The butterflies select flowers based on shape. butterflies are not efficient pollinators as they are highly perched on their long thin legs. Unlike bees that can hover while feeding, butterflies need a place to land because they cannot feed while flying. 

Bees are one of the most efficient pollinators. In the United States, there are 4000 species of native bees. Familiar bees visiting garden flowers are the colorful, fuzzy, yellow-and-black striped bumblebees, metallic-green sweat bees, squash bees, and imported honey bees. 

Beetles co-evolved with primitive flowering trees, such as magnolias. Beetle-pollinated flowers are very fragrant, large, and bowl-shaped. The shape makes it easier for the clumsily-flying beetles to land within the flower, where they eat their way through petals and other floral parts. They even defecate within flowers, earning them the nickname “mess and soil” pollinators.

Flower flies such as syrphids masquerade as bees and wasps but have only one pair of wings. Putrid-smelling blossoms are an adaptation to attract specific fly pollinators.

Male mosquitoes (relatives of flies) get in on the act since they pollinate specific orchids. In the tropics, minute fig wasps have co-evolved with fig plants. This partnership has been highly successful. Today, there are more than nine hundred species of fig plants, each with its wasp species. 

Cross Pollination with Unusual Pollinators

The flowers have enlisted the aid of some very unique pollinators. Honey Possums, charming big-eyed, long-nosed marsupial mammals native to Australia, drink nectar from Banksia blooms. Black-and-white Ruffed lemurs on Madagascar Islands are the pollinators of the traveler’s tree (Ravenala madagascariensis). Off the coast of New Zealand, A giant island gecko found in coastal New Zealand moves pollen between flowers of New Zealand flax (Phormium Tenax) plants.

Bottom Line

Pollination, quite simply, is the way many plants reproduce. Since plants are immobile, they require assistance with their reproduction, and that’s where the role of pollinators comes in.

Cross-pollination is an essential ecological function and not just natural history. More than eighty percent of the world’s flowering plants require a pollinator for reproduction. Animals assisting the plants in their reproduction as pollinators include species of bats, bees, butterflies, moths, flies, birds, beetles, and ants.

If many plants aren’t properly pollinated, they cannot bear fruit or produce new seeds with which to grow new plants. On a small scale, a lack of pollination results in a fruitless tree; on a large scale, it could mean a shortage to our food supply. Consequently, if you do not have pollinators, Earth’s terrestrial ecosystems and the human race would not survive. 

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