Tag: plants: structure and function

The C₁₅ backbone of ABA is formed after cleavage of C_{40 Carotenoids.}

Seed dormancy is mainly caused by ABA. Dormancy allows seeds to tolerate desiccation and extremes of temperature better. Due to its action of inducing dormancy in seeds, buds etc. ABA is also called as dormin.

Lemon juice helps keep the apple from browning, because it is full of ascorbic acid (Vitamin C) and it has a low (acidic) pH level. Ascorbic acid works because oxygen will react with it before it will react with the polyphenol oxidase. However, once the ascorbic acid gets used up, the oxygen will start reacting with the enzyme and browning will occur. Lemon juice's low pH level also helps prevent browning. Polyphenol oxidase works best when the pH level is between 5.0 and 7.0. However, below a pH level of 3.0, the enzyme becomes inactivated. The pH of lemon juice is in the 2.0 range, making it very effective against browning.

Abscissic acid regulates abscission (the shedding of leaves, flowers and fruits from the living plant) and dormancy. It acts as general plant growth inhibitor and also inhibit plant metabolism. It inhibits closure of stomata in epidermis, and increase tolerance of plant to various kinds of stresses, and therefore called as stress hormone.
ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps seeds to withstand dessication and other factors favourable for growth.

Abscisic acid is the hormones also called as stress hormones as they function in stress conditions. They are also known as dormant as they induce dormancy in buds. It mostly induced bud dormancy at the start of the winter season. They are generally growth hormone which inhibits growth normally.

Dormancy is the period when the physiological activities of the plant slow down for some time. Abscisic acid is a stress hormone that is responsible for the protection of plants in drought conditions. They are generally growth inhibitors and are also called as dormants. They are mainly responsible for the bud dormancy at the time of winter season and also cause seed dormancy and protect it from desiccation.

Abscisic acid inhibits seed germination and stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone.

A plant will abscise apart either to discard a membrane that is no longer necessary, such as a leaf during autumn or a flower following fertilization or for the purpose of reproduction. Most deciduous plants drop their leaves by abscission before winter, whereas evergreen plants continuously abscise their leaves.

The nucellus is a part of the inner structure of the ovule, forming a layer of diploid (sporophytic) cells inside the integuments. It is structurally and functionally equivalent to the megasporangium. In some plants, the diploid tissue of the nucellus gives rise to a seed through a mechanism of asexual reproduction called nucellar embryony.

The fruit of the coconut is a large, dry drupe composed of a thin outer layer (exocarp), a thick, fibrous middle layer called as a mesocarp and a hard inner layer called as an endocarp that surrounds a large seed. A small, cylindrical embryo is embedded in the endosperm nutritive tissue just opposite the functional germination pore. The seed is surrounded by an outer brown layer called as the seed coat or testa.
Thus, the correct answer is option D.