Biology Test 40

In old trees, the greater part of secondary xylem is dark brown due to deposition of organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils in the central or innermost layers of the stem.

These substances make it hard, durable and resistant to the attacks of microorganisms and insects. This region comprises dead elements with highly lignified walls and is called heartwood.

Intercalary meristems are present at the base of leaves above the nodes. They are a part of apical meristems, which get separated from the apex due to the development of permanent tissue in between. It helps to increase the length of internodes and thus the length and NOT the girth of the axis. It helps regenerate part of grasses removed by grazing herbivores.

Phloem tissue in angiosperms is composed of Sieve tubes, companion cells, phloem parenchyma and phloem fibres or bast fibres. Albuminous cells are associated with sieve cells hence present in gymnosperms.

Family Leguminosae includes shrubs and trees found in both temperate and tropical areas. It comprises of the largest families of flowering plants. The leaves are stipulate and range from pinnately compound to simple. The petiole base is commonly enlarged into pulvinus. The perianth commonly consists of a calyx and corolla of five segments each. In this the petals are overlapping in bud with the posterior petal outermost in position. The androecium consists of 10 stamens in two groups and are diadelphous. The pistil comprises of a single style and stigma.

The stem of a plant may be modified to perform different functions. They can be modified to store food. For example, underground stems of potato and ginger. Stems can be modified to form straight and pointed thorns. Thorns are the formed from the Axillary buds of the stems. For example, the citrus has thorns. Spines are the modified parts of leaves such as extension of leaf veins. They commonly contain vascular tissue. For example, the plants of cactus family have spines. Prickles are the extension of cortex and epidermis and are comparable to hairs. For example, rose plant has prickles.

Ciliated columnar epithelium lines respiratory tract (lower end of bronchi), fallopian tubes, ventricles of brain (ependyma), central canal of spinal cord, etc.

The most widely distributed tissues of body, connective tissue consist of cartilage, bone, adipose tissue, loose and embryonic connective tissue, and blood. Connective tissue has cells, fibers, amorphous and ground substances.

Striated muscles are voluntary muscles i.e., under our control. These muscles are attached to bones and are under our will. Striated muscles are involved in movement of arms, face, legs etc.

Cockroach (an insect) excretes uric acid as the chief nitrogenous excretory product.

Reasoning- All of the above options are forms of food storage adventitious roots.

Tubercular roots store food in bunches, nodulose roots store food in their root tips and annulated roots forms series of swollen rings. Moniliform roots/ Beaded roots form swollen beads like structures at regular intervals for food storage.