Problem 169 - Objective Biology for NEET

Question

Assertion: Custard apple is example of aggregate fruit Reason: It is developed from flower having polycarpellary apocarpous gynoecium.

Step-by-Step Solution

Answer

The assertion is correct, and the reason is valid. A Custard apple is indeed an example of an aggregate fruit as it is grown from a flower that possesses a polycarpellary apocarpous gynoecium.

Step 1: Understand the Definition of Aggregate Fruit

An aggregate fruit is a fruit that develops from a single flower that has more than one separate carpels, which are mature ovaries of the flower. Each carpel contains one or more seeds.

Step 2: Understand the Meaning of Polycarpellary Apocarpous Gynoecium

Polycarpellary refers to the presence of multiple carpels. Apocarpous means these carpels are free from each other. Gynoecium refers to the female reproductive part of the flower.

Step 3: Evaluate the Characteristics of Custard Apple

A Custard apple is an example of an aggregate fruit as it is developed from a flower which has a polycarpellary apocarpous gynoecium. This means that the flower of the Custard apple has several independent carpels, each maturing into a separate section of the fruit.

Step 4: Formulate Conclusion

Since a Custard apple is developed from a flower having polycarpellary apocarpous gynoecium and also fits the definition of an aggregate fruit, the assertion that a Custard apple is an example of an aggregate fruit is correct, and the reason stated is valid and correctly explains why the Custard apple is an aggregate fruit.

Key Concepts

Polycarpellary Apocarpous Gynoecium

The term polycarpellary apocarpous gynoecium might seem complex, but it's a straightforward botanical concept once broken down. Polycarpellary refers to a flower's female reproductive part, the gynoecium, having multiple carpels. A carpel is the individual unit of the gynoecium and includes an ovary which contains the potential seeds, or ovules, along with the style and stigma.

In contrast to united carpels (syncarpous), the apocarpous arrangement means these multi carpels are not fused together and remain distinct. This structure can be pivotal for the development of certain types of fruits, particularly aggregate fruits. Each separate carpel has the potential to become a small fruit on its own, but together they form what we recognize as a single, aggregated entity.

To visualize this, think of each carpel as a slice of a pie that hasn't been cut. In an apocarpous gynoecium, these slices remain whole and separate, while in a syncarpous gynoecium, they would be fused into a single piece. This character is prominently seen in plants like the Custard apple (Annona squamosa) and blackberries.

Plant Reproduction

Understanding the polycarpellary apocarpous gynoecium is crucial in grasping the broader context of plant reproduction. Flowers are the reproductive structures of angiosperms (flowering plants), where the union of male and female gametes takes place. The process begins from the moment a flower blooms, ready to carry out sexual reproduction.

When we talk about plant reproduction, we're referring to how plants generate offspring to continue their species. This can occur in two main ways: sexual and asexual reproduction. In sexual reproduction, which is our focus here, the key actions happen within the flowers. The female parts (gynoecium) play an essential role, as ovarian tissues within the carpels develop into seeds upon fertilization by the male gametes, carried by pollen from the stamens (the male reproductive parts).

Once the ovules are fertilized, the ovaries mature into fruits, which may be a single fruit from a syncarpous gynoecium or an aggregate fruit from an apocarpous gynoecium. Breeders and botanists pay close attention to these reproductive structures to understand fruit development, seed dispersal, and plant diversification.

Mature Ovaries in Flowers

The magic of plant reproduction culminates in the development of mature ovaries within flowers, leading to fruit formation. The mature ovaries, essentially, are the part of the plant that transforms into the fruit — which we might intentionally cultivate, harvest, and consume, or which might serve in seed dispersal in the wild.

Within each carpel lies the ovary containing ovules. Post-fertilization, these ovules become seeds, and the ovary grows into a fruit that encases them. The type of fruit that develops is deeply interconnected with the arrangement of the carpels. In the case of a polycarpellary apocarpous gynoecium, you'll find that each carpel can develop into a separate segment of an aggregate fruit, like a raspberry or a blackberry.

Ripening signifies the final stage, where the fruits reach their mature state, changing color, texture, and often increasing in sugar content and aroma — these changes signal to potential seed dispersers, like animals, that the fruit (and thus, the seeds within) is ready. Understanding this process is crucial for those who work in agriculture, horticulture, or simply enjoy the natural wonder of how a single flower can give rise to a multitude of fruits.