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Introduction

A modified and condensed shoot useful for reproduction in angiosperms is called a flower. Flowers are often described as a modified stem. The gynoecium is an essential part of the flower as it contains the female reproductive organisms. 


Carpel and pistil are the two female reproductive organism units in flower, the part which you see from outside. Carpel is a long stick-like structural part in the flower that comprises a mixture of three essential parts; stigma, style, and ovary - the female parts of a flower. There can be one or more carpels present in a flower. 


The pistil consists of stigma, ovary, and style, and is generally fused along with the female reproductive parts. 


Let’s peer inside the structure of the carpel. The ovary is the basal, swollen part inside the bud, which is a fertile part in the carpel. If there is only one carpel, the ovary is called unilocular, which means chamber. If there are two, three, or five carpels fused with each other, that is, a polycarpellary syncarpous condition, then the ovary is bilocular, trilocular, or pentalocular. Each chamber of the ovary contains one to many small globular structures called ovules or megasporangia. Ovules are produced on a soft fertile tissue called the placenta. Different modes of arrangement are exhibited within the ovary. 


Style is a narrow elongated threadlike tubular structure that connects the ovary with the stigma. The terminal part of the carpel which receives pollen grains during the process of pollination is called stigma. Pollen germination happens during that specific time. Stigma is generally rough and sticky in nature. When all three parts of a carpel are fused together, it is called pistil. Therefore, the collection of fused carpels is called pistils in the case of syncarpous. 

What is a Carpel

Carpels are composed of the stigma, style, and ovary, the female parts of a flower. Flowers can have one or more carpels. It can also be defined as the fourth whorl of the flower present in the centre. 

What is a Pistil

The word pistol is derived from the Latin term pistillum, pestle. It can either be the same as an individual carpel as it comprises stigma, style, ovary, or a carpel fused together. This means a pistil can have lots of carpels.

 

The major difference between the carpel and pistil is that the carpel is a single reproductive unit (bisexual organism), while the pistil is the collection of fused ovaries.  Carpel has seed production, while pistils do not. The ultimate goal of the carpel is to disperse the seed, while the pistil works as the female reproductive system of the flower. Carpel produce eggs, while pistils do not. Fertilisation happens for carpels but not for pistils.


Important Facts Regarding Flower

1. Gynobasic style is a characteristic feature of the family labiate (Ocimum), where style arises from the depression or cavity in the center of the ovary or directly from the thalamus. 

2. Feather-like stigma is called the plumose stigma, as in grasses (Gramineae).

3. Receptacle is the modified, flattened pendulous on which flowers lie in a specific manner.

4. An additional whorl of bract is called an involucre.

5. Gynoecium is considered a modified leaf (megasporophyll).

6. Rafflesia arnoldii has the largest flower. 

7. Long filamentous threads protruding at the end of a young cob of maize are style.

8. The colored sepals other than green color are called sepaloid. Example: Garden nasturation.

9. The term staminode is given to reduced or non-functional stamens. Example: Saliva.

10. If only one carpel is present in the gynoecium, then this condition is called the monocarpellary condition.

11. If more than one carpel is present in the gynoecium, then this condition is known as polycarpellary.

12. When all carpels are fused, this condition is called syncarpous. Example: mustard and tomato.

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