Anatomy Of Flowering Plants

Xylem functions as a conducting tissue for water so Xylem will be coloured red with safranin. And Phloem will be coloured green with fast green.

Hence the correct answer is option (a).

Meristem is group of actively dividing cells which help in growth occurring in plants.

Parenchyma performs various functions like photosynthesis, storage, secretion.

Collenchyma provides mechanical support to the growing parts of the plant such as young stem and petiole of a leaf.

Sclerenchyma is either fibres or sclereids based on variation in form, structure, origin and development.

Epidermal Tissue is a system that forms the outer covering of the whole body plant and this system contains epidermal cells, stomata and the epidermal appendages – the trichomes and hairs.

Hence the correct answer is option (b).

Cuticle is a waxy thick layer covering the outside if the epidermis and it prevents the loss of water.

Bulli form cells are the modified adaxial epidermal cells along the veins in grasses. Bulliform cells are large, empty, colourless cells.

Out of many stomata present in the epidermis of the leaves, each stoma has two bean shaped cells called guard cells.

Epidermis is the outermost layer of the primary plant body. They are usually single layered.

Hence the correct answer is option (a).

Parenchyma, collenchyma and sclerenchyma are simple tissue system.

Simple tissue is made of only one type cells and so the origin of simple tissue is homogenous.

Xylem and Phloem are complex tissues found in all vascular plants.

Epidermis is also complex in nature as it may contain stomata.

Hence the correct answer is option (a).

Xylem is conductive complex tissue, transports water and mineral and is usually dead in nature, so option (a) is not correct.

Sclerenchyma consists of long, narrow cells with thick and lignified cell walls but they are usually dead. So option (b) is incorrect.

Collenchyma consists of cells which are thickened at the corners due to deposition of cellulose, hemicellulose and pectin. They provide mechanical support to the growing parts of the plant.

Epidermis is the outermost layer of the primary plant body. They are usually single layered.

Hence the correct answer is option (c).

Epidermis is the outermost layer of the primary plant body. They are usually single layered.

In case of root, it is called epiblema instead of epidermis.

Stele is collective term for all tissues present on the innerside of the endodermis like pericycle, vascular bundles and pith.

Endodermis and Pericycle are the part of root or stem encircling vascular strands.

Hence the correct answer is option (c).

A conjoint and open vascular bundle will be observed in the transverse section of dicot stem.

Vascular bundles are arranged in a ring in dicot stem.

Each vascular bundle is conjoint, open, and with endarch protoxylem.

Monocot stem has a large number of scattered vascular bundles. Here vascular bundles are conjoint and closed.

And open bundles are present only in pats where secondary growth is possible and only dicot stem is capable of secondary growth.

Hence the correct answer is option (d).

Interfascicular cambium and cork cambium are formed due to Cell dedifferentiation.

The permanent tissue regenerate to become meristematic layer by the process called Cell dedifferentiation.

Cell differentiation – is the process which lead to maturation of cells.

A differentiated cell can regain its capacity for cell division under certain conditions. This phenomenon is called dedifferentiation.

A dedifferentiated plant cell once again loses its capacity to divide and becomes mature. This phenomenon is called redifferentiation.

Hence the correct answer is option (c).

Phellogen and Phellem respectively denote Cork cambium and cork.

Due to activity of vascular cambium the stem continue to increase girth-wise. So the outer cortical and epidermis layers get broken and are replaced by new protective cell layers.

So in cortex region another meristematic tissue develops called Cork Cambium or Phellogen.

Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem.

Hence the correct answer is option (b).

Root tip and shoot tip have meristematic tissue as root tip and shoot tip is an actively growing part of the plant. The cells in this region are highly active and keep dividing. So, the cells do not get differentiated to epidermal tissue, so epidermis is absent in root and shoot tips.

Hence the correct answer is option (a).

Four apical meristems are present at the tip of four branches and one is present at the growing apex of the main plant axis. So, five shoot apical meristems are likely to be present in a twig of a plant possessing 4 branches and 26 leaves.

Apical meristems is always present at the growing apices.

Hence the correct answer is option (c).

A piece of wood having no vessels (trachea) must belong to pine tree.

Trachea is absent in gymnosperms i.e., pine tree. Instead it has trachieds.

All the other trees show angiosperms and presence of vessels (trachea) is a characteristic feature of angiosperms.

Hence the correct answer is option (c).

A plant tissue, when stained, showed the presence of hemicellulose and pectin in cell wall of its cells. The tissue represents collenchyma.

Collenchyma is a group of specialized cells meant for mechanical support. It has the thickening at the corners of the cells which is mainly because of the deposition of pectin and hemicellulose.

Hence the correct answer is option (a).

In conifers fibres are likely to be absent in secondary xylem.

Elongated cells of sclerenchyma are called Fibres. And Sclerenchyma is absent in secondary xylem.

Hence the correct answer is option (b).

When we peel the skin of a potato tuber, we remove periderm.

In some small woody stem and many non-woody stem, the epidermis is replaced with periderm. Periderm is a kind of cork.

Potato is an underground stem. The outer epidermal layer of this underground stem is known as periderm.

Hence the correct answer is option (a).

A vessel less piece of stem possessing prominent sieve tubes would belong to Trochodendron.

The species of Trochodendron genus have a very unique feature of the angiosperms, i.e., it lack vessel (trachea) elements in its wood, but has prominent sieve tube cells. This is quite unusual for flowering plants.

Hence the correct answer is option (d).

Phellogen cell types always divide by anticlinal cell division.

In anticlinal cell division the plane of division is at right angles to the surface of the plant body. That is Anticlinal cell divisions are perpendicular to the adjacent layer of cells.

Phellogen divides this way.

Hence the correct answer is option (d).

The fate of primary xylem in a dicot root showing extensive secondary growth is that it is retained in the centre of the axis.

Primary xylem is present in the centre of the root. As secondary growth occurs in the root the primary phloem is pushed outside whereas, primary xylem remains inside the root.

Hence the correct answer is option (a).

Parenchyma stores the product of photosynthesis before being transported or utilised by the various parts of the plants.

Walls of parenchyma are thin and made up of cellulose.

The parenchyma is present either in roots and stems or in their modifications in the form of a-polysaccharide called starch.

If the protoxylem lies next to phloem, this type of arrangement of xylem is known as Exarch.

Exarch arrangement is present in roots.

In exarch arrangement the protoxylem lies towards periphery and metaxylem lies towards the centre.

The function of phloem parenchyma is to store food material and other substances like resins, latex and mucilage.

It also helps in translocation of food. They also helps in slow lateral conduction of food.

Cuticle is present on the surface of the leaves which helps the plant prevent loss of water.

Cuticle is absent in roots.

Cuticle is waxy thick layer covering the outside of the epidermis.

The epidermal cell modification in plants which prevents water loss is known as Bulliform Cells.

Bulliform cells are present in grasses. They help in closing the stomata under stressful conditions and this prevents water loss.

(a) Radial Vascular bundle is present in roots. Radial Vascular bundle includes xylem and phloem, and these are present in separate radii of the roots.

(b) Polyarch xylem is present in monocot root. When many strands of xylem are present, it is referred to as polyarch condition-a characteristic feature of monocot root.

(c) Well developed pith is present in dicot stem and monocot roots. Dicot stem and monocot roots have well developed pith formed of parenchymatous cell with intercellular spaces.

The cells that make the leaves curl in plants during water stress are Bulliform cells.

The epidermal cell modification in plants which prevents water loss is known as Bulliform Cells.

Bulliform cells are bubble shaped cells which are present in grasses. They help in closing the stomata under stressful conditions and this prevents water loss.

When the bulliform cells in the leaves have absorbed water and are turgid, the leaf surface is exposed. When they are flaccid due to water stress, they make the leaves curl inwards to minimise water loss.

Interfascicular cambium and Intrafascicular cambium constitutes cambial ring. It is formed due to the meristematic activity of cambium.

The cambium which is found between the xylem and phloem is called intrafasicular cambium and the newly formed cambium between the two vascular bundles is known as interfasicular cambium. Both type of cambium combine to form the cambial ring.

The basic functional difference between phellogen and phelloderm is:

Phellogen is a meristematic tissue and Phelloderm is a permanent tissue.

Phellogen is called as Cork Cambium, Phelloderm is called as Secondary Cortex.

Phellogen develops from the cortical cells, sometimes from pericycle cells. These cells actively divide and forms phellem on outer side.

Phelloderm inner side on so phelloderm takes its origin from phellogen.

Phellogen produces phellem and phelloderm.

Phelloderm stores food materials.

Phellem or cork is the outer most layer, followed by phellogen (cork cambium) which in turn is followed by phelloderm (secondary cortex).

Hence the sequence is as follows:

Phellem → Phellogen → Phelloderm

If one debarks a tree then periderm part (i.e., all tissues exterior to vascular cambium) of the plant is being removed.

Periderm contains phellogen, phellem and phelloderm.

Bark also contains secondary phloem.

The cross-section is of dicot root.

Vascular bundles are present are arranged in alternate manner on separate radii thus called radial arrangement.

Protoxylem is towards periphery of root thus making exarch condition.

Hard wood are wood from angiosperm, whereas soft wood are wood from gymnosperm.

Soft wood are soft due to absence of vessels also known as non-porous wood. It mainly contains tracheids.

Hard wood contains abundant of vessels. In this no trachieds is present.

The stone like structures present in peach or pear are stone cells also known as Sclerieds.

Schlerieds are type of Sclerenchyma which provides mechanical support to organs.

The sclereids are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities (lumen).

The commercial source of cork is cork tissue of Quercus suber.

Due to the activity of vascular cambium the stem increases in girth. So the outer cortical and epidermis layers get broken and need to be replaced by new protective cell layers. Hence another meristematic tissue called cork cambium or phellogen develops in the cortex region.

Phellogen is a couple of layers thick. It is made of narrow, thin-walled and nearly rectangular cells. Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem while the inner cells differentiate into secondary cortex or phelloderm.

The cork is impervious to water due to suberin deposition in the cell wall and provides protection to the underlying tissues.

a. Coir is natural fibre obtained from coconut husk. Coir is mesocarp of coconut. It is the fibrous mesoderm of the coconut fruit Cocosnucifera.

b. Hemp fibre is obtained from the stem of cannabis sativa. It is the bast fibre (soft or stem fibre) obtained from secondary phloem.

c. Cotton fibre is obtained from epidermal growth of cotton seeds. It is elongated structure made up of cellulose.

d. Jute is natural bast fibre is obtained from stem of Corchorus Capsularis. It is made up of cellulose and lignin.

The characteristic differences found in the vascular tissue of gymnosperms and angiosperms are as follows:

Some of modified epidermal cells to perform specialized functions in plants with their functions are as follows:

i. Root Hair: It increases the surface area for absorption of water and minerals from the soils. Root hairs are unicellular elongations of the epidermal cells.

ii. Trichomes: They are also known as stem hairs. They help in water loss prevention during transpiration. Some trichomes have stinging purpose while others have glandular secretions. They may be unicellular or multicellular.

iii. Bulliform cells: Bulliform cells are present in grasses. They help in closing the stomata under stressful conditions and this prevents water loss. Bulli form cells are the modified adaxial epidermal cells along the veins in grasses. Bulliform cells are large, empty, colourless cells.

Meristematic tissue is responsible for the rapid growth of lawn grass.

The meristems which occur at the tips of roots and shoots and produce primary tissues are called apical meristems.

When lawn is mowed the apical meristems get trimmed and the growth of grass stops. But the growth of lateral branches continues making the lawn look bushy.

Plants die when watered in excess, because excess water removes the air trapped between the soil particles.

Plants use water for several metabolic processes as photosynthesis, transpiration and respiration.

Plant when watered excess its roots do not get enough oxygen for respiration. Once root cells die, water and mineral absorption is stopped and this leads to gradual death of a plant.

Hence irrigation should be supported with proper drainage of water to avoid water logging in the soil. Water logging draws salt to the surface of the soil. This salt gets deposited on roots of the plants. This increased salt content is dangerous to the growth of the crops and is extremely damages the plants and plants die.

The growth rings in the trunk of the tree are formed by cambial ring due to secondary growth.

Each ring contains early wood and late wood. Secondary growth occurs in dicot trees due to the activity of cambium which is a meristematic tissue.

The concentric growth rings are called annual rings.

The rate of activity of cambium is more in spring than in winter so wood formed has larger wider xylem cells and called spring wood or early wood, whereas wood formed in winter has narrower and smaller xylem elements and called autumn wood or late wood. And also the wood formed during spring is light-coloured with low density and the wood formed during winter is dark-coloured with high density. This result in the formation of alternate concentric rings called growth rings.

By counting these rings, age of the tree can be determined.

Trunks of some of the aged tree species appear to be composed of several fused trunks. This is anatomical abnormality.

It is an abnormal type of secondary growth, where a regular vascular cambium or cork cambium is not formed in its normal position. In this case cortical and medullary vascular bundles are formed. This gives rise to the additional or accessory vascular bundles giving an appearance of additional trunk which appear to be fused trunk.

The respective functions are as follows:

a. Sieve tube – They help in translocation of synthesized food throughout the plant. It is present in phloem tissue.

b. Interfasicular cambium – It facilitates secondary growth in dicot stem and root and also helps in formation of vascular cambium. It is a kind of secondary meristematic tissue present in between two vascular bundles.

c. Collenchyma – It provides mechanical support to young stem. Its cells have angular thickening at corners.

d. Aerenchyma – It provides buoyancy to floating plants. It is a specialized parenchyma having large air spaces.

The epidermal cells surrounding the guard cells are known as Subsidiary cells.

The difference between guard cell and epidermal cell is as follows:

The differences in the anatomy of leaf of peepal (Ficus religiosa) and maize (Zea mays) are as follows:

Palm is a monocotyledonous plant, yet it increases in girth slowly due to secondary growth. It is due to parenchymatous cell division and enlargement in the ground tissue. Thus, repeated divisions cause increase in girth of stem.

This type of secondary growth is known as Diffused secondary growth.

The monocotyledonous plant does not have primary cambium in the vascular bundles. But in palm a secondary cambium may be formed in the hypodermal region and that forms conjunctive tissue and meristematic cells.

The meristematic cells form new tissues to increase the girth of the stem.

Placenta is a tissue which is flattened, cushion-like tissue. Through placenta ovule is attached to the wall of the ovary.

Placentations are of many types like marginal, axile, pariental, basal, central and free central.

In Marginal Placentations the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, as in pea. This is found in monocarpellary, unilocular ovary.

In Axile Placentations the ovules are borne on central axis and the marginal of placenta grow inward and fuse, thus making a multilocular ovary, as in China rose, tomato, etc. Here numbers of locules are as many as the carpels.

In Parietal Placentations the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one chambered but it becomes two chambered due to the formation of a false septum known as replam, e.g., mustard, argemone. Here the placentae develop on the ovary wall and the number of placentae is equal to the number of carpels.

In Free Central Placentations the ovules are present on the central axis of ovary and septa is absent so ovary is unilocular, as in Dianthus and Primose. A single large swollen placenta arises from base of the ovary. It bears a number of ovules all over its surface.

In Basal Placentations the placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold, etc.

Placenta function is to supply nutrients to the developing embryo.

Apart from physiological changes the other anatomical mechanism involved in the abscission of leaves are as follows:

i. Structural: In deciduous trees, an abscission zone also known as separation zone is formed at the base of the petiole. It is composed of top layer and bottom layer. The cells in the top layer have weak cell walls and the bottom layer expand in winter and break the cell walls of the top layer, this result in shedding of leaves.

ii. The loss of chlorophyll may also result in abscission process.

iii. Hormonal: Abscisic acid hormone stimulates abscission.

An abscission layer is formed at the junction of the leaf and stem, it prevents transport of substances to and from the leaves and causes death of leaf cell thereby shedding of leaves takes place.

Anatomically, the cells of abscission zone are thin-walled and without deposition of lignin or suberin. At the time of abscission, the middle lamella may dissolve between the cells of two middle layers but the primary wall remains intact. The middle lamella as well as the primary walls of the adjacent cells is dissolved. Ultimately the whole cells of middle layer found in the abscission layer gets dissolve completely. Thus, there is separation of plant organ, i.e., leaf from the plant, wherever there is rainfall or wind.

Evergreen trees are tree which shed their leaves throughout the year as they are covered with leaves all the time. These are persistent in all four seasons. In contrast to deciduous plants which completely loose their foliage during winter or dry season.

Pinus does not shed its leaves during a particular season and is always evergreen. Hence Pinus is considered as an evergreen tree belongs to gymnosperms.

So Pinus is evergreen, coniferous resinous tree.

The leaves in gymnosperms are well-adapted to withstand extremes of temperatures, humidity and wind.

In conifers, the needle-like leaves reduces the surface area. Their thick cuticle and sunken stomata also help to reduce water loss.

The flowering plants under conditions of extreme cold shed their leaves and become dormant. But Pinus due to the presence of bark, which is thick, needle-like leaves having sunken stomata, reduce the rate of transpiration. The cold areas are physiologically and physically dry due to scanty rainfall, precipitation as snow, decreased root absorption at low temperature and exposed habitats. But, Pinus is well adapted to such conditions. It continues to manufacture food during this period and grown to dominate other plants. This shows that Pinus is an evergreen tree. It does not shed its leaves, i.e., needles under any condition.

Assuming a plant cell division it can be cut vertically, horizontally and diagonally.

Thus, it can be cut into three planes, through three axes, i.e., x, y and z.

When any plane passes through the central axis of the plant cell, it divides the cell into two identical halves; it is called Radial Symmetry (figure below shows radial symmetry)

If the plant cell can be divided into identical left and right halves in only one vertical plane, exhibit bilateral symmetry (figure below shows bilateral symmetry)

a. Plasmodesmata – A microscopic channels between two cells through the cell wall are called Plasmodesmata. Plasmodesmata allow transport of materials between two cells. They are protoplasmic strands between adjacent plant cells.

b. Middle lamella – It is a layer in the cell wall and is made of calcium pectate (mainly) and magnesium pectate. It helps in cementing between two neighbouring cells. During ripening a fruit becomes soft and pulpy due to dissolution of middle lamella.

c. Secondary wall – this is a non-extensible layer. It is made of hemicelluloses. It provides rigidity to the cell. The cell wall of a young plant cell is capable of growth, which gradually diminishes as the cell matures and the secondary wall is formed on the inner (towards membrane) side of the cell. Secondary cell wall may have the deposition of lignin. Secondary wall helps in the differentiation of the cell.

a. Exarch and endarch

b. Stele and vascular bundle

c. Protoxylem and metaxylem

d. Interfasicular cambium and intrafasicular cambium

e. Open and closed vascular bundles

f. Stem hair and root hair