Pollination in plants – Part 1

In today’s blog, we will attempt to explain Pollination- Its impact and reasons for failure. This will provide a better insight into reasons of why fruiting and flowering may not be occurring as expected.

What is pollination?

It is the process of transfer of pollen grains from the anther of a male flower to the stigma of the female flower.

  • Stamen/Anther- a male reproductive part which contains pollen grains.
  • Pollen grains- these are the male microgametophytes which produce male gametes (sperm cells).
  • Pistil/Stigma- female reproductive organ of a plant.

The significance of pollination:

In order to have a continuous life cycle, a living organism must produce their own progenies. And plants are no exceptions to this natural cycle. Plants continue their progenies by producing seeds for the next generation.

Pollination increases the percentage of fruit set in a flower. Later, the fruit will produce the seed.

Pollination is naturally aided by wind, insects, water, rain etc.

Types of pollination:

  1. Self-pollination –when pollen grain from one flower pollinate the stigma of the same flower or other flowers from the same plant. Here most of the crops are self-fertile; i.e they do not require any vector for the pollination.Self Pollination in a flower
  2. Cross-pollination – It is the transfer of pollen grain from one flower to the stigma of a flower on another plant which belongs to the same group of species. Cross-pollination occurs through vectors like insect or wind or water etc.

Cross-pollination in a flower

 

 

Challenges & remedies in a controlled environment:

When plants are grown in protected structures, there is a restriction on wind/rain/insects movement. This leads to a lacking or improper pollination which results in no fruit set or deformed fruits and seeds. In such case, manual/hand pollination is required i.e to pollinate the flowers manually.

Before we attempt this, however, it is essential to understand the basic botany of a plant. Ex: What are male, female, hermaphrodite or bisexual plants??

The male flower consists only of male reproductive part (androecium)

Male flower of a cucumber plant

 

The female flower consists only of female reproductive part (gynoecium)

Female flower of a Cucumber plant

 

A Bisexual/Hermaphrodite flower consists of both male and female reproductive parts in a single flower, which are largely self-pollinating group plants.

Bisexual or Hermaphrodite Flower

 

Monoecious are single plant bears both male and female flowers in separate structures
Ex. Cucumbers, squashes, pumpkins.

Dioecious are plants where male flower bearing and female flower-bearing plants are 2 separate or different plants.
Ex.asparagus, spinach.

Both the monoecious and dioecious group of plants require cross-pollination.

 

Hand pollination in cucurbits

Gourds are monoecious in nature and cross-pollination is normally aided through insects. Insects collect pollen and nectar from the flowers as food. As they forage, they spread the pollen from one flower to another flower, one plant to another plant.

But when plants are grown in protected structures, the insect movement is restricted. Hence no pollination occurs in the flowers. Or very meager pollination may occur through wind/water/rain. Due to this, yield reduces in the plants. This is where the manual/hand pollination is beneficial.

Steps for manual Hand pollination:

  • First, check for the male and female flowers.
  • Using a small plant brush collect the pollen grains from anthers of the male flower
  • Smear them on the stamen of the female flower. Or take the male flower and give a gentle tap over the stigma of the female flower.

One needs to be careful so as not to damage the stigma – a damaged stigma would lead to unfruitfulness.

A good read on fruiting and some challenges are explained in an earlier blog.

Stay tuned for further details on flower openings and on dehiscence, and stigma receptivity timings. These would be crucial for a good yield.

Happy Gardening!

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