Question 1

What is meant by modification of root?What type of modification of root is found in the:(a) Banyan tree (b) Turnip(c) Mangrove trees

Accepted Answer

Primarily, there are two types of root systems found in plants, namely the tap root system and fibrous root system. The main function of the roots is to absorb water and minerals from the soil. However, roots are also modified to perform various other functions. The roots of some plants act as storage sites for food, some provide support to massive plant structures, while others absorb oxygen from the atmosphere.Roots and its modifications in various plants:(a) Banyan treeThe banyan tree (Ficus benghalensis) has massive pillar-like adventitious roots arising from the aerial part of the stem. These roots grow towards the ground and provide support to the tree. Such, roots are called as prop roots.(b) TurnipThe roots of turnip (Brassica rape) help in the storage of food. Similar food-storing roots are found in radishes, carrots and sweet potatoes.(c) Mangrove treeThe roots of mangrove plants grow vertically upwards from the soil for the absorption of oxygen from the atmosphere as the soil is poorly aerated. These types of roots are called as pneumatophores.

Question 2

Justify the following statements on the basis of external features:(i) Underground parts of a plant are not always roots.(ii) Flower is a modified shoot.

Accepted Answer

(i) Various parts of plants are modified into underground structures to perform various functions such as stems, leaves and even fruits.The stems in ginger and banana are underground and swollen due to storage of food. They are called as rhizomes. Similarly, corm is an underground stem in Colocasia and Zamin-khand. The tips of the underground stem in potato become swollen due to the accumulation of food and forms tuber. Tubers bear eyes, which are subtended by a leaf scar. Basal leaves in onions become fleshy because of the accumulation of food. In peanuts, the flower after fertilization gets pushed into the soil by growing a flower stalk. The formation of fruits and seeds takes place inside the soil.(ii) During the flowering season, the apical meristem gives rise to the floral meristem. The axis of the stem gets condensed, while the internodes lie near each other. Instead of leaves, various floral appendages arise from the node. Therefore, it can be said that the flower is a modified shoot.

Question 3

How is a pinnately compound leaf different from a palmately compound leaf?

Accepted Answer

Pinnately compound leaf: The leaflets are attached to the common axis, called as rachis.Examples include neem and Cassia fistula (also called as golden shower plant).Palmately compound leaf: The leaflets are attached at a common point on the leaf stalk.Examples include silk cotton (Bombax) and Cannabis.

Question 4

Explain with suitable examples, the different types of phyllotaxy.

Accepted Answer

Phyllotaxy refers to the pattern or arrangement of leaves on the stem or branch of a plant. It is of three types: alternate, opposite and whorled phyllotaxy.In alternate phyllotaxy, a single leaf arises from the node of a branch. This type of phyllotaxy is observed in the sunflower, mustard and peepal. Plants with opposite phyllotaxy have two leaves arising from the node in opposite directions. It is found in guava and jamun plants. Plants with whorled phyllotaxy have three or more leaves arising from the node. It is found in Alstonia.

Question 5

Define the following terms:(a) Aestivation (b) Placentation (c) Actinomorphic(d) Zygomorphic (e) Superior ovary (f) Perigynous flower(g) Epipetalous stamen

Accepted Answer

(a) Aestivation:The term ‘aestivation’ refers to the mode in which sepals or petals are arranged in a floral bud with respect to other floral members. There are four types of aestivation in plants, i.e., valvate, twisted, imbricate, and vexillary.(b) Placentation:The term ‘placentation’ refers to the arrangement of ovules within the ovary of a flower. It is primarily of five types, namely marginal, basal, parietal, axile and free central.(c) Actinomorphic:Actinomorphic flowers can be divided into two radial halves by any radial plane passing through its centre. Examples of these flowers include chilly and mustard.(d) Zygomorphic:Zygomorphic flowers are those flowers which can be divided into two similar halves by a single vertical plane. Examples of these flowers include pea and beans.(e) Superior ovary:Superior ovary flowers are those flowers in which the gynoecium is present at the highest position, while other floral parts are arranged below it. A flower with this arrangement is described as hypogynous. Examples include brinjal and mustard.(f) Perigynous flower:In perigynous flowers, the gynoecium is present in the centre and the rest of the floral parts are arranged at the rim of the thalamus at the same level. Examples include plum and rose.(g) Epipetalous stamen:Epipetalous stamens are stamens attached to the petals. They are found in brinjal.

Question 6

Differentiate between (a) Racemose and cymose inflorescence(b) Fibrous root and adventitious root(c) Apocarpous and syncarpous ovary

Accepted Answer

(a) Racemose inflorescence Cymose inflorescenceYounger flowers are present at the tip while older flowers are arranged at the base of this inflorescence. Such an arrangement is called acropetal succession.Younger flowers are present at the base of the inflorescence, while older flowers are present at the top. Such an arrangement is called basipetal succession.The main axis in racemose inflorescence continues to grow and produce flowers laterally.The main axis in cymose inflorescence has limited growth, which later terminates into a flower. (b) Fibrous root Adventitious rootIn monocots, the primary root which develops from the radicle of the seed is short-lived and is replaced by a large number of roots arising from the base of the stem.These roots arise from any part of the plant other than the radicle of seeds.It is found in wheat and other cereals.It is found in banyan, Monstera, and other plants. (c) Apocarpous ovary Syncarpous ovaryThe flowers with apocarpous ovary have more than one carpel. These carpels are free.The flowers with syncarpous ovary have more than one carpel. However, these carpels are fusedIt is found in lotus and rose flowers.It is found in the flowers of tomato and mustard.

Question 7

Describe modifications of stem with suitable examples.

Accepted Answer

Stems of various plants have undergone modifications to perform different functions.1. Underground stems or storage stems:Examples: Rhizomes, Corms, tubersIn ginger and banana, the underground stem is called as a rhizome. The underground stem in Colocasia (arvi) is known as corm. Rhizomes and corms are underground stems, modified for the storage of food. Also, these stems help in vegetative reproduction of these plants. The tips of the underground stem in potato plants become swollen due to the accumulation of food. The potato is a tuber that helps in the storage of food and bears eyes on it. Subtended by a leaf scar, these eyes bear buds that give rise to new plants.2. Supportive stems:Example: tendrilThe stem in some weak plants bears thin, slender and spirally-coiled structures called as tendrils that help the plant get attached to nearby structures for support. Tendrils are found in cucumbers, melons and other members of the family Cucurbitaceae.3. Protective stems:Example: ThornsThe stem in Bougainvillea and citrus plants (like lemon and orange) bear sharp, pointed structures called as thorns, which provide protection to the plant from herbivores.4. Photosynthetic stems:Example: OpuntiaThe stem in the Opuntia is green. It carries out the process of photosynthesis in the absence of leaves.5. Others stem modifications:In some plants, underground stems such as grasses spread in the soil and help in perenation. These stems are called as runners.The short lateral stem called as the offset in some aquatic plants (such as Eichhornia) bears leaves and tufts of roots at the node and gives rise to new plants.

Question 8

Take one flower each of the families Fabaceae and Solanaceae and write its semi-technical description. Also draw their floral diagram after studying them.

Accepted Answer

(1) Family Fabaceae/Papilionaceae (pea plant) : Fabaceae/Papilionaceae is a sub-family of the Leguminoseae family.Vegetative features :Habit : Pinnately compound, alternately arranged with leaf tendrils with the pulvinus present at the leaf base along folacious stipules.Root : Tap root system with root nodules.Floral features :Inflorescence : Racemose, generally axial than terminalFlower : Zygomorphic and bisexual flowers are found.Calyx : It contains five sepals which are gamosepalous while aestivation is imbricate.Corolla : It contains five petals (polypetalous) with vexillary aestivation.Androecium : It consists of ten anthers that are diadelphous with dithecous anthers.Gynoecium : Monocarpellary superior ovary which is unilocular with marginal placentation.Fruit : Legume pod with non-endospermic seeds.Economic importance: Peas are used as vegetables for making various culinary preparations.(2) Flowers of Solanum nigrumVegetative features :Habit : Erect, herbaceous plantLeaves : Simple, exstipulate leaves with reticulate venationStem : Erect stem with numerous branches.Floral features : Inflorescence : Solitary and axillaryFlowers : Actinomorphic, bisexual flowersCalyx : Calyx is composed of five sepals that are united and persistent. Aestivation is valvate.Corolla : Corolla consists of five united petals with valvate aestivation.Androecium : It consists of five epipetalous stamens.Gynoecium : It consists of bicarpellary syncarpous superior ovary with axile placentation.Fruits : Berry Seeds: Numerous, endospermousEconomic importance : Used for medicinal purposes.

Question 9

Describe the various types of placentations found in flowering plants.

Accepted Answer

Placentation refers to the arrangement of ovules inside the ovary. It is of five basic types:(A) Marginal placentation-The ovary in which the placenta forms a ridge along the ventral suture of the ovary and the ovules develop on two separate rows is known to have marginal placentation. This type of placentation is found in peas.(B) Parietal placentation-When the ovules develop on the inner walls of the ovary, the ovary is said to have parietal placentation.C) Axile placentation-In axile placentation, the placenta is axial and ovules are attached to it. Examples include China rose, lemon and tomato.(D) Basal placentation-The ovary in which the placenta develops from its base and a single ovule is found attached to the base is said to have basal placentation. It is found in marigold and sunflower.(E) Free central placentation-In free central placentation, the ovules develop on the central axis while the septa are absent. This type of placentation is found in Dianthus and primrose.

Question 10

What is a flower? Describe the parts of a typical angiosperm flower.

Accepted Answer

Flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction. A typical flower has four different kinds of whorls arranged successively on the swollen end of the stalk or pedicel, called thalamus or receptacle. These are calyx, corolla, androecium and gynoecium.Calyx and corolla are accessory organs, while androecium and gynoecium are reproductive organs. In some flowers like lily, the calyx and corolla are not distinct and are termed as perianth. Some flowers have both androecium and gynoecium and are termed hermaphrodite flowers while some flowers have only one of these two whorls.Calyx : The calyx is the outermost whorl of the flower and its units are called sepals. Generally, sepals are green, leaf like and protect the flower in the bud stage. The calyx may be gamosepalous (sepals united) or polysepalous (sepals free).Corolla : Corolla is composed of petals. Petals are usually brightly coloured to attract insects for pollination. Like calyx, corolla may also be free (polypetalous) or united (gamopetalous). The shape and colour of corolla vary greatly in plants. Corolla may be tubular, bell-shaped, funnel-shaped or wheel-shaped.Androecium : Androecium is the male reproductive part of the flower. It is composed of stamens. Each stamen which represents the male reproductive organ consists of a stalk or a filament and an anther. Each anther is usually bilobed and each lobe has two chambers, the pollen-sacs. The pollen grains are produced in pollen-sacs. A sterile stamen is called staminode.Gynoecium : Gynoecium is the female reproductive part of the flower and is made up of one or more carpels. A carpel consists of three parts namely stigma, style and ovary. Ovary is the enlarged basal part, on which lies the elongated tube, the style. The style connects the ovary to the stigma. The stigma is usually at the tip of the style and is the receptive surface for pollen grains. Each ovary bears one or more ovules attached to a flattened, cushion-like placenta. When more than one carpel is present, they may be free (as in lotus and rose) and are called apocarpous. They are termed syncarpous when carpels are fused, as in mustard and tomato. After fertilisation, the ovules develop into seeds and the ovary matures into a fruit.

Question 11

How do the various leaf modifications help plants?

Accepted Answer

The main function of the leaves is to carry out the process of photosynthesis. However, in a few plants, leaves are modified to perform different functions.(a) Tendrils: The leaves of a pea plant are modified into tendrils that help the plant in climbing.(b) Spines: The leaves in cactus are modified into sharp spines that act as an organ of defence.(c) Phyllode: The leaves of some Australian acacia are short-lived and soon replaced by flattened, green structures called as phyllodes that arise from the petiole of the leaves. The petioles in these plants synthesize food.(d) Pitcher: The leaves of the pitcher plant are modified into pitcher-like structures, which contain digestive juices and help in trapping and digesting insects.

Question 12

Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.

Accepted Answer

The arrangement of flowers on the floral axis is termed as inflorescence. A flower is a modified shoot wherein internodes do not elongate and the axis gets condensed. The apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower, it is always solitary. Depending on whether the apex gets converted into a flower or continues to grow, two major types of inflorescence are defined - racemose and cymose. In racemose type of inflorescence the main axis continues to grow, the flowers are borne laterally in acropetal succession. In cymose type of inflorescence the main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipeta! order.

Question 13

Write the floral formula of a actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carpels with superior ovary and axile placentation.

Accepted Answer

The floral formula of the described flower is represented as:Actinomorphic flowers are represented by the symbol A bisexual flower is indicated by The calyx contains five united sepals which can be represented as K5.The corolla consists of five free petals and it represented as C5.The androecium consists of five free stamens and is represented by A5.The gynoecium consists of a superior ovary with two united carpels and axile placentations, which can be represented as

Question 14

Describe the arrangement of floral members in relation to their insertion on thalamus.

Accepted Answer

In a typical flower, the floral members like calyx, corolla, androecium and gynOecium are arranged over the thalamus! Based on the position of calyx, corolla and androecium in respect to ovary on thalamus, the flowers are described as hypogynous, perigynous and epigynous ones. In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal. If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior or sub superior, e.g., plum, rose, peach. In epigynous flowers, the margin of thalamus grows upward enclosing the ovary completely and gets fused with it; the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.

Chapter 5 : Morphology of Flowering Plants