Polyembryony Flashcard

Polyembryony is the development of multiple embryos from a single ovule or seed, resulting in several embryos within the same seed, which are genetically identical to each other but distinct from the parent plant.

Antonie van Leeuwenhoek first documented polyembryony in 1719.

Polyembryony results in multiple embryos from a single egg, while budding involves new individuals arising from a part of the parent organism, leading to genetically identical offspring.

Nucellar embryony is a type of polyembryony where multiple embryos develop from cells in the nucellus, a tissue surrounding the ovule.

Polyembryony is frequently observed in fruit crops like mangoes and citrus fruits.

Nucellar seedlings are virus-free and can serve as true-to-type rootstocks with greater vigor compared to those from vegetative propagation.

Strictly monoembryonic species have less than 6% occurrence of multiple embryos, typically producing a single embryo per seed.

True polyembryony occurs when two or more embryos arise from the same embryo sac, originating from various sources such as the nucellus or synergid cells.

Citrus, mango, and jamun are examples of plants that display true polyembryony.

False polyembryony involves multiple embryo sacs within a single ovule, each sac giving rise to one or more embryos.

Gametophytic polyembryony occurs when multiple embryos develop from gametic cells within the embryo sac, which can be haploid or diploid.

Sporophytic polyembryony arises when multiple embryos develop from sporophytic cells of the ovule, such as the nucellus, resulting in diploid embryos genetically similar to the parent plant.

Adventitious polyembryony is where additional embryos develop from maternal tissues other than the fertilized ovule.

Cleavage polyembryony involves the formation of multiple embryos from a single fertilized egg cell.

Pine, Cedrus, and Tsuga are gymnosperms that commonly show cleavage polyembryony.

Simple polyembryony occurs when multiple embryos develop from fertilization of more than one egg or archegonium.

Argemone Mexicana and Ulmus Americana both exhibit mixed polyembryony, with embryos forming through various mechanisms.

The Necrohormone Theory suggests that polyembryony results from the degeneration of cells in the nucellus, releasing substances that stimulate additional embryo formation.

The Hybridisation Theory attributes polyembryony to genetic recombination during hybridisation, which may lead to multiple embryos within a single seed.

Polyembryony aids in producing genetically uniform seedlings, preserving desirable traits, and enabling efficient propagation and breeding.

It ensures the production of true-to-type seedlings, enhances breeding programs, and enables efficient propagation of fruit trees.

In conifers, polyembryony can involve multiple fertilized egg cells or adventitious embryos from tissues like the nucellus, enhancing reproductive success and genetic diversity.

In Taxales (yews), polyembryony may result in multiple embryos from a single or multiple fertilized egg cells, aiding in seedling establishment and persistence in their environment.

Polyembryony in Gnetales is rare but can involve multiple embryos from a single or multiple fertilized egg cells, contributing to reproductive success and species dispersal.

Strictly monoembryonic species produce less than 6% multiple embryos per seed, typically resulting in a single embryo per seed.

Nearly monoembryonic species have a 6% to 10% frequency of multiple embryos, indicating a moderate occurrence of polyembryony.

Polyembryonic species produce more than 10% multiple embryos per seed, showing a high frequency of polyembryony.

In Cycadales, polyembryony can enhance survival and dispersal by producing multiple seedlings from a single seed, especially in harsh environments.

Polyembryony is used to produce true-to-type, virus-free seedlings and can enhance breeding programs by ensuring genetic uniformity and plant vigor.

Polyembryony ensures genetic uniformity, preserves desirable traits, and allows for efficient propagation of fruit trees, leading to high-quality plant material.

Polyembryony increases genetic diversity by producing multiple embryos, which may carry different genetic variations, enhancing adaptability and survival.

Mixed polyembryony involves both cleavage and adventive embryos within a single seed, resulting from various mechanisms.

Citrus plants, mangoes, and Opuntia (prickly pear cactus) exhibit adventive polyembryony, where embryos develop from non-fertilized tissues.

Polyembryony can be induced using chemical treatments like 2,4-D, which can increase the incidence of polyembryony in seeds, though it may result in smaller seeds with reduced growth potential.

Auxin regulation is hypothesized to play a role in polyembryony by influencing developmental processes. Disruptions in auxin levels can lead to the formation of multiple embryos.

Chromosomal irregularities during meiosis or mitosis can lead to polyembryony by causing multiple embryos to form from a single seed.

Polyembryony can lead to uniform seed quality by ensuring that all embryos in a seed are genetically identical, which is beneficial for commercial fruit production and maintaining consistent plant characteristics.

Polyembryony enhances propagation efficiency by producing genetically uniform seedlings that can be used to quickly and reliably reproduce desirable plant traits.

Polyembryony in mangoes results in both zygotic and apomictic embryos, providing uniformity and virus-free seedlings that are advantageous for commercial cultivation.

It allows for precise control over plant genetics, facilitating the development of new varieties with specific traits and improving crop yields through the propagation of uniform plant material.

The Hybridisation Theory suggests that polyembryony arises from genetic recombination during hybridisation, leading to multiple embryos within a single seed due to combined genetic material.

Environmental factors like temperature, soil moisture, and air velocity can affect the frequency and development of polyembryonic seeds.