Steps of Pollen Pistil Interaction

The acceptance of compatible pollen by the pistil and the rejection of self-incompatible pollen by the pistil in the Brassicaceae includes intricate molecular communication mechanisms between the pollen grain and the female reproductive organs. Preference for species-related pollen, paired with self-recognition systems, allows the plant to select the most desirable pollen, increasing the number of successful fertilisation and vigorous progeny. Because the Brassicaceae family includes a broad set of agriculturally important crops as well as several great model organisms for researching both compatible and self-incompatible pollinations, it is an attractive family for studying pollen–pistil interactions.

Pollen Pistil Interaction

Pollen-pistil interaction refers to the sequence of events that occur from pollination to the insertion of pollen tubes into the ovules. During this contact, the pollen grains are screened by the pistil. Pollen from other species is blocked in the style at the level of pollen germination and pollen tube growth. The stigma recognises conspecific pollen grains and activates physiological mechanisms to help them germinate and produce pollen tubes. Even self-pollen is detected and prevented in self-incompatible species. Only the most vigorous suitable pollen grains are chosen for fertilisation. During pollen-pistil interaction, the gametophytic partners (pollen grains and pollen tubes) and the sporophytic partner (the pistil) have a tight discussion. Pollen recognition and subsequent promotion/inhibition are aided by extracellular components found in and on the pollen wall, on the stigma, and along the course of the pollen tube in the style.

Pollen tubes are steered towards the micropyle of the ovule by attractants released by the embryo sac synergids after entering the ovary (ES). In some model systems, such as Torenia and Arabidopsis, the nature of these attractants is known. Through one of the synergids, the pollen tube penetrates the ES and discharges the two male gametes for fertilisation. Some of the intricate details orchestrated by the ES cells in pollen tube guiding, the release of male gametes, double fertilisation, and the cessation of pollen tube attractant discharge.

Steps of Pollen Pistil Interaction

The sequence of events from when pollen is deposited on the stigma to when the pollen tube penetrates the ovule is referred to as pollen-pistil interaction. Pollination, or transporting pollen grains from the anther to the stigma of the same flower or from one bloom to the next, is the initial stage or step in pollen-pistil interaction.

The pollen-pistil interaction occurs in the steps below:

• Real pollen lands on an appropriate pistil in the first instance of pollen-pistil contact.
• Pollen tubes are formed during pollen germination, allowing pollen grains to discharge their contents.
• The pollen tube develops into the ovary through the pistil’s style.
• Male gametes enter the ovule before moving on to the synergid.

Structure of Pistil 

The female reproductive portion of the flower is the pistil, which is located in the centre of the flower. The swelling base, ovary (containing potential seeds or ovules), ovary stalk or style, pollen receptive tip, and stigma, which is variously shaped and frequently sticky, are the main components. The number of pistils in flowers varies a lot depending on the species and how they bloom. The principal function of the pistil, which is made up of one to several leaf-like structures, is to guard the ovules.

Functions of Pistil

 The pistil’s primary job is to create an ovule. The pistil serves a variety of functions, including the following:

• The pistil is the flower’s female reproductive organ in female flowers.
• It helps with pollen reception and fertilisation.
• The pistil is also involved in the germination of pollen grains.
• It also assists in pollen grain movement during pollination.
• The pistil produces the stigma, which has a sticky tip and is necessary for pollen grain germination.

Process of pollen pistil interaction

Pollination is the process of pollen grains falling onto the stigma and germinating to form a pollen tube. The presence of a pollen grain on the stigma does not guarantee that the stigma will be fertilised. Pollen from one species does not germinate on the stigma of another species, which is known as interspecific incompatibility.

Pollen germination occurs in three stages. Hydration, activation, and pollen tube emergence are the three processes. Pollen grains are dried to make them easier to travel from blossom to flower. Germination occurs after rehydration. The plasma membrane of the pollen grain can reconstruct into an efficient osmotic membrane once it has been hydrated. Activation causes filaments to grow throughout the cytoplasm of cells. As the hydration and activation spread, the pollen tube expands. The anthers of flowering plants produce microspores through meiosis. Mitosis occurs, resulting in male gametophytes. Megaspores, on the other hand, are produced by meiosis in the ovules. When pollen grains adhere to the stigma, they germinate and form a pollen tube that grows through the style’s tissues.

Conclusion

The pollen-pistil interaction encompasses all events that occur between the pollen grains landing on the stigma and the pollen tube entering the embryo sac via the ovule. In the event of suitable pollen, the germination of pollen results in the formation of a pollen tube. The pollen tube extends from the style to the ovule. Incompatible pollen inhibits germination and prevents the formation of pollen tubes. Pollination is the process of pollen grains falling onto the stigma and germinating to form a pollen tube. The main function of the pistil is to produce an ovule. The female reproductive portion of the flower is the pistil, which is located in the centre of the flower.