Introduction:
Efficient crosses are essential in plant breeding to obtain desired traits in the offspring. Self-pollination, the process of fertilization within the same individual plant, needs to be avoided for carrying out efficient crosses. This is because self-pollination limits genetic diversity and restricts the introduction of novel alleles into the offspring.

Explanation:
Self-pollination can occur in plants that have both male and female reproductive structures, such as hermaphroditic flowers. In this process, the pollen from the anther (male reproductive organ) is transferred to the stigma (female reproductive organ) of the same flower or a different flower on the same plant. This leads to fertilization and the development of seeds.

Reasons for avoiding self-pollination:
1. Lack of genetic diversity: Self-pollination leads to limited genetic diversity in the offspring. As the same plant is involved in both the male and female roles, the genetic material is not mixed with that of another plant. This reduces the chances of introducing new genetic traits and restricts the variation in the offspring.

2. Inbreeding depression: Continuous self-pollination over generations can lead to inbreeding depression. Inbreeding depression is the loss of vigor and fitness in the offspring due to the accumulation of harmful recessive alleles. This can result in reduced plant growth, lower fertility, and increased susceptibility to diseases and pests.

3. Reduced adaptability: Self-pollination limits the ability of plants to adapt to changing environmental conditions. Genetic diversity is crucial for organisms to adapt to new challenges and survive in diverse ecological niches. Cross-pollination allows for the exchange of genetic material between different individuals, resulting in increased adaptability.

4. Enhanced heterosis: Cross-pollination contributes to heterosis or hybrid vigor, which is the phenomenon where the offspring exhibit improved traits compared to their parents. By crossing plants with different genetic backgrounds, desirable traits can be combined, leading to increased productivity and quality in the offspring.

Conclusion:
To carry out efficient crosses, self-pollination should be avoided. Cross-pollination allows for the introduction of new genetic traits, enhances genetic diversity, and improves the adaptability and productivity of the offspring. By utilizing cross-pollination techniques, plant breeders can successfully develop improved varieties with desired traits.