What is Polyembryony and Parthenocarpy?

Difference Between Polyembryony and Parthenocarpy

Polyembryony:

In several genera of angiosperms, more than one viable embryo in the seed has been observed. It is more frequent in Gymnosperms than in angiosperms. This condition arises in various ways:

  • The oospore produces more than one embryo during development as a result of splitting. This is known as cleavage polyembryony and is very common in gymnosperms (e.g. Pinus) and angiosperms e.g. Allium, citrus, and some orchids.
  • An ovule may contain more than one functional megaspore producing as many embryo sacs and oospheres which on fertilization give rise to more than one embryo in the seed.
  • In addition to the normal embryo produced from a fertilized oosphere, the embryo may also be formed from the synergids (e.g. Dandelion) or rarely the antipodals with or without fertilization.

    (iv) Additional embryos may be produced as a result of saprophytic budding by the division of the cells of the nucellus (e.g. lemon) or integument (e.g. onion).

Parthenocarpy:

Parthenocarpy is the development of fruit without fertilization.

As a rule, the development of the ovule into seeds and the enlargement of the ovary into fruit follow only after pollination and fertilization have occurred. In most species of flowering plants, the failure of pollination results in the failure of seed and fruit formation. This usually happens in mature of pollinating insects are not active or the destruction of pollen occurs. In many kinds of fruit trees, if heavy rains fall during the time when pollen is maturing the pollen grains are washed out of the flowers, pollination does not occur and as a consequence few or no flowers set fruits. In some plants, fruits are formed even in the abundance of pollination and fertilization. Such fruits are always seedless. These are succulent and more desirable than normal seed-containing fruits. They are said to be parthenocarpy, while the phenomenon concerned with their formation is termed Parthenocarpy.


There are two main types of parthenocarpy: natural and artificial.

  • Induced parthenocarpy: When seed-less fruits are produced by spraying the stigmas of flowers with ether or water extract of pollen grains or by injecting such growth-promoting substances as in indole acetic acid and naphthalene acetic acid into the ovaries of plants.
  • Natural parthenocarpy: When seedless fruits are produced without any special treatment from the ovaries in the absence of pollination and fertilization. Familiar examples are the naval oranges, grapes, bananas, and pineapples.

Comments

Post a Comment

Popular posts from this blog

Compare the anatomy of Bifacial and Isobilateral leaves

BIFACIAL LEAF: It is also called dorsiventral leaf. This leaf is more strongly illuminated on upper surface than on lower surface. This unequal illumination induces a difference in the internal structure between upper and lower sides. Its internal structure shows: (1)        Upper Epidermis This is single layer of cells with thick cuticle which checks excessive evaporation of water from the surface. It does not contains chloroplasts, stomata are also absent. (2)        Lower Epidermis This is also single layer but with a thin cuticle. It bears many stomata, two guard cells of which contain some chloroplast, none are present in the epidermal cells. Internal to each stomata is large cavity called respiratory cavity. Lower epidermis of leaf is meant for exchange of gases (oxygen and carbon dioxide) between the atmosphere and the plant body. Excess water also evaporates from lower epidermis. (3)...
Read more

osmoregulation in terrestrial and aquatic animals

Mechanism of osmoregulation is very important for all groups of animals whether inhibting land or water. Unlike plant cells, animal cells when placed in hypotonic solution burst due to the continuous absorption of water. On the contrary they would shrink and die if constantly placed in hypertonic solution. Normally uptake and loss of water are in balance for proper survival of cell. (1)        Osmoregulation in terrestrial animals: Terrestrial animals are more likely to loose water by evaporation through their permeable surfaces exposed to amsophere. Among various animal groups only Arthropods and vertebrates became the most successful land dwellers. They have developed number of strategies to maintain osmoregulation of their body fluid. (a) Water proof external coverings: To prevent water loss through external surfaces, vertebrates like reptiles, birds and mammals have water proof keratinized epidermis. Similarly the insects have developed...
Read more

Autobiographical elements in A Farewell to Arms

Introduction Some, literature can be satisfactorily read and discussed taking the author into account. Other literature seems inseparable from the person who created it. To an extraordinary degree Hemingway and what he has written exist in a synergetic relationship, reinforcing and fulfilling each other; he has created a personal legend which serves as an ambience in which we read him. Autobiographical Touches The novel A Farewell to Arms autobiographical elements. The love-affair between Fredric and Barkley, the hero’s injury in the battlefield, his despair and frustration, the hero’s separate peace with life are some of the characteristics of Hemingway’s life. Hemingway himself had received the injury caused by the mortar-shell at Fossalta, and he was admitted into the Milan hospital for recuperation in the late summer and autumn of 1918. He fell in love with the nurse in the Milan hospital. Carlos Baker has thrown light on this fact. In A Farewell to Arms Hemingway was d...
Read more