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Sepals

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An Introduction to Sepals

IVSAT 2024

The vegetative part of a flower constitutes the sepals and petals. The flowering plant's sepals are linked straight to the top of the stem. They are available in a variety of sizes and shapes. Sepals vary in length and thickness, with some being long and thin and others being short and thick. Some sepals are individually shaped, while others are fused to form a cup around the flower's petals.


The perianth is made up of the calyx and corolla together. Petaloid refers to a perianth that isn't green. It's called sepaloid if it's green in colour.


What are Sepals?

Sepals are modified leaves that make up a flower's outer whorl. They are usually green, although they can be any hue. They envelop the rest of the flower in the bud stage. Depending on the species, flowers have varying number of sepals. However, in some species, they can be missing or prominent and petal-like. Due to the presence of chlorophyll, sepals are capable of photosynthesis. They safeguard the flower's bud.


Functions of Sepals

The sepals’ functions in a flower are as follows:

  • By encapsulating the developing buds in the bud condition, it protects them.

  • Since the sepals of a flower are green, they can also generate food.

  • They also safeguard the flower buds.

  • Some of the sepals that have petaloid attract insects.

  • Fruit dissemination is aided by some sepals.


Calyx

The calyx of the flower refers to all of the sepals together. The epicalyx, or the second layer of sepals, is visible in the hibiscus. Coloured petal-like or petaloid petals of a flower adorn the flame of the forest blooms. When the flower blooms, the sepals may stay on or fall off. Calyx has two patterns that are visible.

  • Plants with joined sepals form a cup-like shape in a gamosepalous flower.

  • Sepals are separated into polysepalous animals.


Corolla

The next whorl toward the apex is the corolla flower part, which is made up of units called petals, which are often thin, delicate, and colourful to attract pollinating creatures. To attract pollinators, the corolla may be fragrant, coloured, or flashy. The inner layers of a flower's critical layers should be protected. One layer or whorl, two layers or double whorl (Poppy), or a spiral (Water lily). The following two patterns can be seen in the corolla:

  • Petals join together to form a tube in gamopetalous flowers. For example, Ipomea and Nerium.

  • Petals are free in polypetalous flowers. Rose and mustard are two examples.


Aestivation in Flowers

The arrangement of petals and sepals in flower buds before blooming is known as aestivation in plants. It is all about the other whorl members. Aestivation is frequently mistaken for vernation, which is the process of arranging new leaves and scales in a leaf bud. Perianth refers to the petals and sepals as a whole. The aestivation of plants is the arranging of perianth inside a flower bud before it blooms. Aestivation is an important element of taxonomy since the aestivation of flowers from various species differs. The following are the five types of aestivation:

  • Valvate

  • Twisted

  • Imbricate

  • Vexillary

  • Quincuncial


Fabaceae Family

Here are the characteristics of the Fabaceae family:

  • Herbs, shrubs, vines, and plants that climb by twining or tendrils belong to this family.

  • Root nodules contain nitrogen-fixing bacteria (rhizobium), and non-protein amino acids are frequently discovered.

  • The leaves are generally pinnatus and spirally organized, with well-developed pulvinas and separate leaflets.

  • Sleep motions are generally seen in the leaf axis and leaflets.

  • The stipules that are present are sometimes big or have spines.

  • Flowers are normally bisexual, with cup-shaped hypanthium petals that are regular or irregular.

  • Sepals are normally five in number, free or connate when a tube with valvate or bilabiate lobes is present.

  • Irregular petals are adaxially small and lie within the laterals in and outside the laterals in III (resupinate sometimes).

  • It's imbricate or basally connate, regular, and valvate.

  • Androecium has one to ten stamens, which are concealed by the perianth and have long-exerted and sometimes showy filaments that are separate or connate.

  • Pollen grains are tricolporate, tricolpate, or triporate if connate is monodelphous or diadelphous.

  • The one-carpel gynoecium is unique, elongated, and has a short gynophore.

  • With parietal (marginal) placentation, the ovary is superior.

  • Campylotropous ovules are anatropous.

  • The majority of fruits are legumes.


Fabaceae Floral Diagram


Fabaceae Floral Diagram


Conclusion

The distinguishing feature of angiosperms is the flower, which is a component of the shoot system. It is the reproductive structure of the plant. They are frequently brightly coloured to attract pollinating insects. Sepals and petals comprise the vegetative part of a plant which helps in the protection of the flower bud.


In botanical terminology, aestivation refers to the arrangement of sepals and petals in flower buds around other members of the whorl. Vernation, which is the arrangement of scales and new leaves in a leaf bud before it opens, is frequently confused with it. A perianth is a combination of sepals and petals. Bud pollination is the term used to describe the process of pollination that takes place when the flower is in bud condition.

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FAQs on Sepals

1. What is the structure of a sepal?

Only flowering plants produce sepals, which are green-coloured vegetative parts of plants. The flower's outermost layer, known as the calyx, encloses the flower bud and is its outermost layer. A stamen is the leaf-like part of a flower. Parenchyma, secretory cells are known as laticifers, tannin cells, and other specialised plant cell organelles make up the majority of the sepals. Depending on the plant species, the sepals have a wide range of colours. The cells of green sepals contain chloroplasts, separate palisade, and spongy mesophylls.

2. What is venation?

Venation is the process of vein creation on the leaf. Reticulate venation is characterised by irregular vein patterns that form a network. Veins are organised into a network and are found predominantly in dicots. One midvein is present, and all other veins create a mesh-like structure in pinnate reticulate venation/unicostate reticulate venation. For example Hibiscus, papaya, Tulsi leaves, coriander, China Rose, Mangifera, etc. In contrast, the veins run parallel to each other in parallel venation, which mostly occurs in monocots.

3. What do you mean by a tepal?

When it is difficult to distinguish between the components of the perianth, such as when the petals and sepals are the same colour or when the petals are absent and the sepals are colourful, the term "tepal" is used to refer to the perianth component in question. They are also referred to as lilioid monocots because they include Liliales in their classification. Plants belonging to genera such as Aloe and Tulipa are examples of those that can be referred to as having tepals. 


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