Advantages and Disadvantages of Cross Pollination

The process of applying pollen from one flower to the pistils of another flower is known as cross-pollination. Pollination occurs naturally through the use of insects and wind. This procedure can also be carried out by hand in order to produce offspring with desired characteristics such as colour or pest resistance.

To cross-pollinate, two different roses at a similar stage of development must be prepared. In general, the tetraploid roses are self-compatible, as opposed to diploid roses, which are mostly self-incompatible. To avoid self-pollination of the chosen seed parent, the anthers (pollen sacs) of the blooms must be removed before any pollen is released. This is best done at sunrise when the blooms are one-third to one-half open. First, the petals are all removed. This method allows for easier access to the flower’s centre. The anthers are then removed with tweezers or small scissors. If the seed parent variety will also be used as a pollen parent with other roses, the anthers can be collected in a cup and placed uncovered in a dry place where they will mature and release pollen the next day. Following emasculation, the remaining portion of the bud is covered with a white paper bag to prevent unwanted pollen from reaching the stigmas.

Cross-Pollination

Cross-pollination, also known as hierogamy, is a type of pollination in which sperm-laden pollen grains are transferred from one plant’s cones or flowers to another’s egg-bearing cones or flowers. Cross-pollination occurs in both angiosperms (flowering plants) and gymnosperms (cone-bearing plants), and it aids in cross-fertilization and outbreeding. Pollen movement can occur through wind, as in conifers, or through symbiotic relationships with various animals (e.g., bees and certain birds and bats) that transport pollen from plant to plant while feeding on nectar.

Mechanisms that Prevent Self-pollination

Many flowering plants have evolved to limit self-pollination while allowing for cross-pollination. The structure of a flower, self-incompatibility and the timing of the maturation of stamens and pistils of the same flower or plant can all reduce or eliminate self-pollinations. Cross-pollination can then occur as a result of a variety of agents, the most common of which are insects and wind. Wind-pollinated flowers are distinguished by a lack of colour, odour, or nectar, as well as stigmas that are arranged to capture airborne pollen. Animal-pollinated flowers stand out due to their structure, colour, or ability to produce scent or nectar, all of which evolved in tandem with animal pollinators.

Structural

Many plant species have evolved physical and structural barriers to self-pollination. Some plants, such as date palms (Phoenix dactylifera) and willows (Salix species), have become dioecious, which means that some produces only “male” (stamina) flowers, while others produce only “female” (pistil late or ovule-producing) flowers.

In species with stamina and pistillate flowers on the same individual (monoecious plants) and hermaphroditic flowers (flowers with both stamens and pistils), a common method of preventing self-fertilisation is to have the pollen shed either before or after the period when the stigmas on the same plant are receptive, a situation known as dichogamy. Protandry, in which the stamens ripen before the pistils, is the more common form of dichogamy found in insect-pollinated flowers such as fireweed (Epilobium angustifolium) and salvias (Salvia species). 

Protogyny, the condition in which the pistils mature first, occurs in arum lilies and many wind-pollinated plants, such as grasses—though several grasses, including common varieties of wheat, barley, and oats, are self-pollinated. Avocado comes in both protogynous and protandrous varieties, which are frequently grown together to promote cross-fertilization.

Heterostyly, or variation in the length of the style, is a structural feature of flowers that discourages selfing (neck of the pistil). This is seen in common primrose (Primula vulgaris), wood sorrel (Oxalis), and flax (Linum usitatissimum). In most British primrose populations, for example, roughly half of the individuals have “pin” flowers, which have short stamens and a long style, giving the stigma a position at the flower’s mouth, whereas the other half have “thrum” flowers, which have a short style and long stamens, forming a “thrumhead” at the flower’s opens.

Bees are unable to avoid depositing pollen from one type of flower onto the stigmas of another. The genetic system that regulates flower structure in these primroses is set up in such a way that cross-pollination maintains a 50:50 ratio of pins and thrums. The stamens and styles of purple loosestrife (Lythrum salicaria) flowers are three different lengths to limit self-fertilization.

Chemical

Another mechanism for preventing self-fertilisation is chemical self-incompatibility. In this phenomenon, which is dependent on chemical substances within the plant, pollen may fail to grow on a stigma of the same flower that produced it, or the pollen tube may fail to grow normally down the style to affect fertilisation after germinations.

This is found in white clover (Trifolium repens), cabbage (Brassica oleracea), and a variety of other plants. The process is genetically controlled; it does not have to be absolute and can vary in degree throughout the flowering season. Not surprisingly, chemical incompatibility is rarely found in plants with strong structural or temporal barriers to self-pollination. Apparently, the evolution of just one such mechanism was sufficient for most plant species.

Advantages of Cross-pollination

• The children are healthier
• Seeds are produced in greater quantities and are more viable
• The seeds develop and germinate properly, resulting in healthier plants
• Cross-pollination between two different varieties of the same species, or even two species, results in new varieties

Disadvantages of Cross-pollination

• It is not always certain because a pollinator is always required and may or may not be available at the appropriate time
• Pollen grains must be abundant in order for pollination to occur and as a result, a lot of pollen is wasted
• It is uneconomical for plants because they must produce large, perfumed flowers with nectar to attract insects

Conclusion

The process of applying pollen from one flower to the pistils of another flower is known as cross-pollination. Pollination occurs naturally through the use of insects and wind. Cross-pollination, also known as hierogamy, is a type of pollination in which sperm-laden pollen grains are transferred from one plant’s cones or flowers to another’s egg-bearing cones or flowers. Cross-pollination, also known as hierogamy, is a type of pollination in which sperm-laden pollen grains are transferred from one plant’s cones or flowers to another’s egg-bearing cones or flowers. Cross-pollination occurs in both angiosperms (flowering plants) and gymnosperms (cone-bearing plants), and it aids in cross-fertilization and outbreeding. Many flowering plants have evolved to limit self-pollination while allowing for cross-pollination. Heterostyly, or variation in the length of the style, is a structural feature of flowers that discourages selfing (neck of the pistil). This is seen in common primrose (Primula vulgaris), wood sorrel (Oxalis), and flax (Linum usitatissimum). Another mechanism for preventing self-fertilization is chemical self-incompatibility. In this phenomenon, which is dependent on chemical substances within the plant, pollen may fail to grow on a stigma of the same flower that produced it, or the pollen tube may fail to grow normally down the style to affect fertilisation after germinations.