Botany and Plant Science

In this, the body of ovule is twisted only half way.

Camphylotropous ovule is present in mustard.

It is diploid in nature.

This is a shrub that is found in the shola forests of the Western Ghats in South India.

A. Suberin is a waxy substance found in higher plants. Suberin is the main constituent of cork, and is named after the Cork Oak, Quercus suber. B. Abnormal secondary growth does not follow the pattern of a single vascular cambium, a thick hair clit producing xylem to the inside and phloem to the outside. Some dicots have anomalous secondary growth, e.g. in Bougainvillea, Dracaena. Withania shows normal secondary growth. C. In angiosperms, intercalary meristems occur only in monocots (in particular, grass) stems at the base of nodes and leaf blades and respond to primary growth of stem and root. Hence, B and C are false.

In monocotyledon roots vascular bundles are present as hexarch or polyarch system. Pith is large and well developed. Cambium is absent. Hence, A and D both characters are absent in monocotyledon roots.

Sclereids are a reduced form of sclerenchyma cells with highly thickened, lignified walls. These have a shape of a star. They are small bundles of sclerenchyma tissue in plants that form durable layers, such as the cores of apples and the gritty texture of pears. Sclereids are variable in shape. The cells can be isodiametric, prosenchymatic, forked or elaborately branched. They can be grouped into bundles, can form complete tubes located at the periphery or can occur as single cells or small groups of cells within parenchyma tissues. But compared with most fibres, sclereids are relatively short. Characteristic examples are the stone cells (called stone cells because of their hardness) of pears (Pyrus communis) and quinces (Cydonia oblonga) and those of the shoot of the wax plant (Hoya carnosa). Hence, A, C and D plant species have sclerenchyma cell, referred to as stone cells.

Haplostele - consisting of a cylindrical core of xylem surrounded by a ring of phloem. An endodermis generally surrounds the stele. A centrarch (protoxylem in the center of a metaxylem cylinder) haplostele is prevalent in members of the rhyniophyte grade, such as Rhynia. Actinostele - a variation of the protostele in which the core is lobed or fluted. This stele is found in many species of club moss (Lycopodium and related genera). Actinosteles are typically exarch (protoxylem external to the metaxylem) and consist of several to many patches of protoxylem at the tips of the lobes of the metaxylem. Exarch protosteles are a defining characteristic of the lycophyte lineage. Plectostele - a protostele in which plate-like regions of xylem appear in transverse section surrounded by phloem tissue. In fact, these discrete plates are interconnected in longitudinal section. Some modern club mosses have plectosteles in their stems. The plectostele may be derived from the actinostele. Solenostele - if the cylinder of vascular tissue contains no more than one leaf gap in any transverse section (i.e. has non-overlapping leaf gaps). This type of stele is primarily found in fernstems today. Eustele - in this arrangement, the primary vascular tissue consists of vascular bundles, usually in one or two rings around the pith. In addition to being found in stems, the eustele appears in the roots of monocot flowering plants. The vascular bundles in a eustele can be collateral (with the phloem on only one side of the xylem) or bicollateral (with phloem on both sides of the xylem, as in some Solanaceae). Hence, A is the only unmatched pair.

They are found in fruit or seed walls and also in the flesh of apples and pineapple. The cells may be living or dead, but short and variously shaped. Their cell wall is heavily thickened with many pit lines unevenly distributed.

Epiblema is the outermost covering of the root formed by single layer of compactly arranged, barrel-shaped parenchyma cells. The cells are characteristically thin-walled, since they are involved in absorption of water. A cuticle and stomata are absent. Some of the epiblema cells are produced into long unicellular projections called root hairs. Hence, the epiblema is also known as piliferous layer.

Medullary parenchyma is the parenchyma which is found radially arranged in between the vascular bundles in the stem. It is meant for storage of reserve food.

Mesophyll is the ground tissue that occurs between the two epidermal layers. It is exclusively composed of chlorenchyma cells. The mesophyll is characteristically differentiated into two regions namely, an upper palisade parenchyma and a lower spongy parenchyma.

The single-celled haploid spore germinates, dividing by the normal process (mitosis), which maintains the number of chromosomes at n. The result is a multi-cellular haploid organism, called the gametophyte (because it produces gametes at maturity).

It is the innermost layer of cortex formed by compactly arranged barrel-shaped cells. Some of the cells in the endodermis are thin-walled and are known as passage cells. The passage cells allow water to pass into the xylem vessels. 

Endodermis is the inner most layer of cortex represented by a single layer of compactly arranged barrel-shaped parenchyma cells. In the stem, it is meant for storage. In the root, it plays an important role in the movement of absorbed water. Some of the cells in the root endodermis contain secondary thickenings called casparian thickenings, formed by a waxy substance called suberin.