Botany and Plant Science

Statement (a) is wrong because it reverses the facts - maize is a monocot with polyarch xylem, while bean is a dicot with tetrarch xylem. Statement (b) is correct because xylem and phloem are radially arranged in roots. Statement (c) is correct because dicot roots typically have tetrarch xylem while monocot roots are polyarch.

Statement (a) is wrong because phloem parenchyma is absent in monocots and present in dicots. Statement (b) is correct - the starch sheath (endodermis) is present in dicot stems. Statement (c) is correct - hypodermis is collenchymatous in dicots and sclerenchymatous in monocots.

Mesophyll tissue is the ground tissue system located between the upper and lower epidermis in leaves. It contains chloroplasts and is the primary site of photosynthesis, consisting of palisade and spongy parenchyma.

Meristematic tissue cells are isodiametric with dense cytoplasm and prominent nuclei, maintaining the ability to divide. Permanent tissues have lost dividing ability and attained definite forms and sizes, performing specific functions.

Statement (b) is wrong because the arrangement of phloem toward upper epidermis and xylem toward lower epidermis applies only to leaves, not all vascular bundles universally. In stems, xylem is typically toward the center. Statement (a) is correct, (c) is correct, and (d) is correct.

Companion cells are specialized parenchyma cells found only in angiosperms. They are closely associated with sieve tube elements in phloem tissue and provide metabolic support, loading and unloading sugars into the sieve tubes.

The starch sheath (also called endodermis) in the dicot stem is the innermost layer of the cortex. In roots, the homologous structure is the endodermis, which performs the same function - regulating movement of substances into the vascular cylinder and containing starch grains. The endodermis is present in both stems and roots but is most conspicuous as a starch sheath in dicot stems.

The xylem is the primary water-conducting tissue in plants. Sap (water and dissolved minerals) moves upward through the hollow lumens of dead xylem vessel elements and tracheids. This transpiration stream is driven by water potential gradients created by transpiration from leaves. Phloem transports organic nutrients (sugars), pith is a storage tissue, and casparian cells are part of the endodermis.

Aerenchyma is a specialized parenchyma tissue with large intercellular air spaces. It provides buoyancy to aquatic plants and facilitates internal gas transport. Hydrophytes (water-living plants) like water hyacinth, lotus, and submerged aquatic plants extensively develop aerenchyma in their stems, roots, and leaves. Epiphytes grow on other plants, xerophytes are adapted to dry conditions, and mesophytes grow in average moisture conditions - none typically require aerenchyma.

Plants that do not have well-differentiated body are called thallophytes. Examples are Spirogyra, Ulothrix, Cladophora and Chara.

Cotyledons represent a bit of pre-designed plant in the seed. There can either be one cotyledon or two cotyledons.

Veins (vascular bundles) form the leaf's skeleton, providing structural support and conducting water, minerals, and sugars. Petiole is the leaf stalk. Arteries are animal blood vessels. Stipules are small outgrowths at the leaf base.

The stem's primary functions are support (holding leaves, flowers, fruits) and conduction (transporting water, minerals, sugars via xylem and phloem). Absorption occurs mainly through roots. Fixation refers to roots anchoring the plant.