Botany and Plant Science

Xylem is a complex vascular tissue composed of four main cell types: tracheids, vessels, xylem parenchyma, and xylem fibers. Sieve tubes are specialized cells used for transporting food and are a primary component of phloem, not xylem. Therefore, sieve tubes are the odd one out in this list.

Sclerenchyma cells are dead at maturity, meaning they lack a living protoplast, including the nucleus and vacuoles. Living tissues like chlorenchyma, aerenchyma, and collenchyma contain large central vacuoles to maintain turgor and store substances. While meristematic cells have very small vacuoles, sclerenchyma is the most appropriate choice among the options as it is completely dead.

As a plant grows older, the outer protective layer is replaced by cork cells. These cells produce and deposit suberin in their walls, which is a waxy, fatty substance that is highly impermeable to water and gases. This makes the cork an excellent protective and insulating layer.

Collenchyma is a living mechanical tissue that provides support while allowing for growth and flexibility. Its cell walls are thickened with cellulose and pectin, which gives it the ability to stretch. This allows young stems and leaf stalks to bend in the wind without snapping.

Phloem is a complex tissue made of sieve tubes, companion cells, phloem parenchyma, and phloem fibers, all working together to transport food. Tracheids are specialized water-conducting cells that are a component of the xylem tissue. Therefore, tracheids are not part of the phloem system.

Phloem tissue consists of four types of cells: sieve tubes, companion cells, phloem parenchyma, and phloem fibres. While the first three are living cells, phloem fibres (also known as bast fibres) are sclerenchymatous cells that are dead at maturity.

Collenchyma is a simple permanent tissue that provides flexibility and mechanical support. It is typically found in the hypodermis of dicotyledonous stems and in the petioles and midribs of leaves, just below the epidermis.

The tip of the root contains the apical meristem, which consists of actively dividing cells. This meristematic tissue is responsible for the primary growth and elongation of the root as it pushes through the soil.

Phloem fibres, or bast fibres, are composed of sclerenchyma cells which have thick secondary walls. These walls are heavily impregnated with lignin, a complex polymer that provides rigidity and strength to the tissue.

  Cortex primarily contributes to the formation of nodules, particularly in legume family.

Root hairs are found only in the zone of maturation, and not the zone of elongation, possibly because any root hairs that arise are sheared off as the root elongates and moves through the soil.

Mustard flowers typically have six stamens arranged in a tetradynamous condition, where four are long and two are short. This is a characteristic feature of the Brassicaceae (Cruciferae) family. This arrangement helps in the identification of plants within this family.

The anther is the part of the stamen (the male reproductive organ of a flower) that produces and contains pollen grains. Sepals and petals are non-reproductive parts that protect the bud and attract pollinators.

Parenchyma is a type of simple permanent tissue having unspecialised cells with thin cell walls. It is living, loosely packed and provides support to plants. It also stores food, nutrients and water.