MORPHOLOGY OF FLOWERING PLANTS

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Shanon Barnard Harmon
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MORPHOLOGY OF FLOWERING PLANTS THE ROOT In majority of the dicotyledonous plants, the direct elongation of the radicle leads to the formation of primary root which grows inside the soil.

In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots.

1 MORPHOLOGY OF FLOWERING PLANTS THE ROOT In majority of the dicotyledonous plants, the direct elongation of the radicle leads to the formation of primary root which grows inside the soil. It bears lateral roots of several orders that are referred to as secondary, tertiary, etc. roots. The primary roots and its branches constitute the tap root system, as seen in the mustard plant. In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots. These roots originate from the base of the stem and constitute the fibrous root system, as seen in the wheat plant. In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots.

The main functions of the root system are absorption of water and minerals from the soil, providing a proper anchorage to the plant parts, storing reserve food material and synthesis of plant growth

2 The main functions of the root system are absorption of water and minerals from the soil, providing a proper anchorage to the plant parts, storing reserve food material and synthesis of plant growth regulators. Regions of root Region of maturation - The cells of the elongation zone gradually differentiate and mature. Hence, this zone, proximal to region of elongation, is called the region of maturation Region of elongation - The cells proximal to the region of meristematic activity undergo rapid elongation and enlargement and are responsible for the growth of the root in length. Region of meristematic tissues - The cells of this region are very small, thin-walled and with dense protoplasm. They divide repeatedly.

3 Root cap - The root is covered at the apex by a thimble-like structure called the root cap. It protects the tender apex of the root as it makes its way through the soil Modification of roots: Tap root - carrot, turnip. Tap roots of carrot, turnip and adventitious roots of sweet potato, get swollen and store food Prop root- banyan tree. Hanging structures that support a banyan tree Stilt root maize, sugarcane. Stems of maize and sugarcane have supporting roots coming out of the lower nodes of the stem Pneumatophores- rhizophora (mangroves). In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground and grow vertically upwards. The Stem: The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits. It develops from the plumule of the embryo of a germinating seed. The stem bears nodes and internodes. The regions of the stem where leaves are born are called nodes while internodes are

the portions between two nodes. The stem bears buds, which may be terminal or axillary. Stem is generally green when young and later often become woody and dark brown.

4 the portions between two nodes. The stem bears buds, which may be terminal or axillary. Stem is generally green when young and later often become woody and dark brown. The main function of the stem is spreading out branches bearing leaves, flowers and fruits. It conducts water, minerals and photosynthates. Some stems perform the function of storage of food, support, protection and of vegetative propagation. Modification of stem: 1. Storage - potato, ginger, tturmeric (perennation) 2. Tendrils axillary buds coils - support (watermelon) 3. Thorns - axillary buds citrus (protection) 4. Flattened stem opuntia (do photosynthesis) 5. Vegetative propagation (grass, jasmine, banana)

The Leaf: Short apical meristem gives rise to leaves arranged in acropetal order Do photosynthesis Three main parts are leaf base, petiole and lamina (leaf blade) Have stipules Leguminous petioles

5 The Leaf: Short apical meristem gives rise to leaves arranged in acropetal order Do photosynthesis Three main parts are leaf base, petiole and lamina (leaf blade) Have stipules Leguminous petioles have pulvinus. (midrib) Venation - arrangement of veins and veinlets on a leaf. Types of venation: Parallel- monocot leaves, When the veins run parallel to each other within a lamina, the venation is termed as parallel Reticulate dicot leaves, When the veinlet forms a network, the venation is termed as reticulate

6 Types of leaves: 1. Simple leaves - A leaf is said to be simple, when its lamina is entire or when incised, the incisions do not touch the midrib. 2. Compound leaves - When the incisions of the lamina reach up to the midrib breaking it into a number of leaflets, the leaf is called compound. Pinnately compound -. In a pinnately compound leaf a number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf as in neem. Palmately compound- In palmately compound leaves, the leaflets are attached at a common point, i.e., at the tip of petiole, as in silk cotton.

Phyllotaxy: Pattern of arrangement of leaves on the stem /branch. 1. Alternate- In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner. Eg. China rose 2 Opposite-.

7 Phyllotaxy: Pattern of arrangement of leaves on the stem /branch. 1. Alternate- In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner. Eg. China rose 2 Opposite-. In opposite type, a pair of leaves arise at each node and lie opposite to each other. Eg. Guava 3. Whorled- If more than two leaves arise at a node and form a whorl, it is called whorled. Eg. Alstonia Modification of leaves: 1. Tendrils - pea (support) 2. Spines - cacti (protection, water ioss)

8 3. Storage - onion/ garlic 4. Petiole leaves acacia 5. Pitcher leaves insectivorous plant (venus fly trap) The inflorescence: Arrangement of flowers on the floral axis Types of inflorescence: Depending on whether the apex gets converted in to a flower/continues to grow there are two major types; 1. Racemose. Main axis continues to grow laterally (in an acropetal succession) 2. Cymose. Main axis terminates in a flower so limited growth (basipetal order)

The flower: Four whorls. Sepal, petal, gynoecium, and androecium Thalamus/receptacle Trimerous/tetramerous/pentamerous/polymerous Bracteates/ebracteate/bract.

9 The flower: Four whorls. Sepal, petal, gynoecium, and androecium Thalamus/receptacle Trimerous/tetramerous/pentamerous/polymerous Bracteates/ebracteate/bract. (Protective sheet around the flower) Bisexual/unisexual Actinomorphic (mustard ) zygomorphic ( pea ) asymmetric ( canna ) Based on the position of ovary: 1. Hypogynous ovary ( mustard ) superior 2. Perigynous ovary (rose ) half inferior 3. Epigynous ovary (guava, cucumber ) inferior

10 Parts of flower: 1. Calyx. Made of sepals. Can be gamosepalous/polysepalous 2. Corolla. Made of petals. Gamopetalous/ polypetalous Aestivation: Arrangement of sepals/ petals in floral bud Main types are Valvate- When sepals or petals in a whorl just touch one another at the margin, without overlapping (petunia alba, calotropis) Twisted - If one margin of the appendage overlaps that of the next one and so on (china rose ) Imbricate- If the margins of sepals or petals overlap one another but not in any particular direction (gulmohur) Vexillary- In pea and bean flowers, there are five petals, the largest (standard) overlaps the two lateral petals (wings) which in turn overlap the two smallest anterior petals (keel); this type of aestivation is known as vexillary or papilionaceous.

11 3. Androecium. Staminode- sterile stamen Epipetalous. Attached to the petal Epiphyllous- attached to the perianth Polyadelphous- Free stamens Monoadelphous- united as one bunch ( china rose ) Diadelphous united two bundles ( pea ) Polyadelphous many bundles ( citrus ) 4. Gynoecium- one/ more carpels Ovules attached on the wall of ovary called placenta. Apocarpous - Free carpels ( lotus, rose ) Syncarpous - Carpels are fused (mustard, tomato )

12 After fertilization ovules devopls into seed. Ovary develops into fruit Placentation: Arrangement of ovules within the ovary. Different types are Marginal- In marginal placentation 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. Axile- When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentaion is said to be axile, as in china rose, tomato and lemon Parietal- In parietal placentation, the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes twochambered due to the formation of the false septum, e.g., mustard and Argemone. Free central- When the ovules are borne on central axis and septa are absent, as in Dianthus and Primrose the placentation is called free central. Basal- In basal placentation, the placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.

The Fruit Parthenocarpic fruit: Formation of fruits

Pericarp has outer epicarp, middle mesocarp and inner

13 The Fruit Parthenocarpic fruit: Formation of fruits without fertilization of ovary. Ex. Seedless grapes, seedless orange. Two parts of a fruit are pericarp and seeds. Pericarp has outer epicarp, middle mesocarp and inner endocarp Both mango and coconut are known as drupe fruits (fruits formed from single ovary /carpel)

14 Perianth: Fused petals and sepals. The Seed Fertilized ovules. Made up of seed coat and an embryo Embryo with radical and plumule with one cotyledon or two cotyledon Structure of a dicot seed: Seed coat, Testa and tegmen Hilum - small pore (place where it is attached to fruit) Micropyle. (water enters) Endosperm, cotyledons, embryonal axis (plumule and radicle) Mature seeds in dicot do not have endosperm called non-endospermic seeds. ( stored food is utilized by embryo) Structure of monocotyledonous seed:

Mostely endosperm except orchids Endosperm is bulky and store food Aleurone layer (produce enzymes to hydrolise proteins for embryo ) Cotyledon is scutellum Protective coats- coleoptiles (piumule ),

15 Mostely endosperm except orchids Endosperm is bulky and store food Aleurone layer (produce enzymes to hydrolise proteins for embryo ) Cotyledon is scutellum Protective coats- coleoptiles (piumule ), coleorhizae ( radical ) Semi technical description of a typical flowering plant: Scientific language Floral diagram and floral formula Floral formula by symbols: Br K - Bracteate - Calyx G - Inferior ovary

16 C P A G G - Corolla - Perianth - Androecium - Gynoecium -Superior Ovary Description of some important families Fabaceae: This family was earlier called Papilionoideae, a subfamily of family Leguminosae. It is distributed all over the world. Vegetative Characters Trees, shrubs, herbs; root with root nodules Stem: erect or climber Leaves: alternate, pinnately compound or simple; leaf base, pulvinate; stipulate; venation reticulate. Floral characters Inflorescence: racemose Flower: bisexual, zygomorphic Calyx: sepals five, gamosepalous; valvate/imbricate aestivation Corolla: petals five, polypetalous, papilionaceous, consisting of a posterior standard, two lateral wings, two anterior ones forming a keel (enclosing stamens and pistil), vexillary aestivation Androecium: ten, diadelphous, anther dithecous Gynoecium: ovary superior, mono carpellary, unilocular with many ovules, style single Fruit: legume; seed: one to many, non-endospermic Floral Formula:

Economic importance Many plants belonging to the family are sources of pulses (gram, arhar, sem, moong, soyabean; edible oil (soyabean, groundnut); dye (Indigofera); fibres (sunhemp); fodder

17 Economic importance Many plants belonging to the family are sources of pulses (gram, arhar, sem, moong, soyabean; edible oil (soyabean, groundnut); dye (Indigofera); fibres (sunhemp); fodder (Sesbania, Trifolium), ornamentals (lupin, sweet pea); medicine (muliathi). Solanaceae It is a large family, commonly called as the potato family. It is widely distributed in tropics, subtropics and even temperate zones. Vegetative Characters Plants mostly herbs, shrubs and rarely small trees Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid or hollow, hairy or glabrous, underground stem in potato (Solanum tuberosum) Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate Floral Characters Inflorescence: Solitary, axillary or cymose as in Solanum Flower: bisexual, actinomorphic Calyx: sepals five, united, persistent, valvate aestivation

Corolla: petals five, united; valvate aestivation Androecium: stamens five, epipetalous Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen with many ovules Fruits: berry

18 Corolla: petals five, united; valvate aestivation Androecium: stamens five, epipetalous Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular, placenta swollen with many ovules Fruits: berry or capsule Seeds: many, endospermous Floral Formula: Economic Importance: Many plants belonging to this family are source of food (tomato, brinjal, potato), spice (chilli); medicine (belladonna, ashwagandha); fumigatory (tobacco); ornamentals (petunia).

19 Liliaceae Commonly called the Lily family is a characteristic representative of monocotyledonous plants. It is distributed worldwide. Vegetative characters: Perennial herbs with underground bulbs/corms/ rhizomes Leaves mostly basal, alternate, linear, exstipulate with parallel venation Floral characters Inflorescence: solitary / cymose; often umbellate clusters Flower: bisexual; actinomorphic Perianth tepal six (3+3), often united into tube; valvate aestivation Androecium: stamen six, 3+3, epitepalous Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with many ovules; axile placentation Fruit: capsule, rarely berry Seed: endospermous Floral Formula: Economic Importance Many plants belonging to this family are good ornamentals (tulip, Gloriosa), source of medicine (Aloe), vegetables (Asparagus), and colchicine (Colchicum autumnale).

20 SOME IMPORTANT QUESTIONS 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 Answer: Sometimes, roots are modified to serve some functions other than its main function of providing anchorage and absorption of water and minerals. a. Banyan Tree: In banyan trees, hanging roots come out from branches. The hanging roots then go into the soil to provide additional support to the huge banyan tree. Such roots are called prop roots. b. Turnip: The tap root in turnip is modified for food storage. c. Mangrove trees: Mangrove trees are found in marshy area. In such plants, many roots come out vertically above the ground. These are hollow roots and are called pneumatophores. They facilitate exchange of gases in the roots. Question 2. Justify the following statements on the basis of external features:

21 (i) Underground parts of a plant are not always roots. Answer: In some plants, stems are also underground for some additional purpose; like food storage and vegetative propagation. Presence of scaly leaves on potato and ginger shows that they are not roots rather stems. (ii) Flower is a modified shoot. Answer: Flower comes out of stem hence it is a shoot. It serves the special purpose of sexual reproduction. Hence, flower is called a modified shoot. Question 3. How is a pinnately compound leaf different from a palmately compound leaf? Answer: Leaflets are present on a common axis (rachis); in case of pinnately compound leaves. In palmately compound leaves, the leaflets originate from the apex of the midrib. Question 4. Explain with suitable examples the different types of phyllotaxy. Answer: Phyllotaxy: The arrangement of leaves on the stem or branch is called phyllotaxy. There are three types of phyllotaxy, which are as follows: a. Alternate: In this type of leaf arrangement, a single leaf arises at each node in alternate manner, e.g. China rose, mustard, sunflower, etc. b. Opposite: In this type of leaf arrangement, a pair of leaves arise at each node. The leaves lie opposite to each other in this case, e.g. Calotropis, guava, etc. c. Whorled: In this type of leaf arrangement, more than two leaves arise at a node, e.g. Alstonia. Question: 5. Define the following terms: (a) aestivation (b) placentation (c) actinomorphic (d) zygomorphic (e) superior ovary (f) perigynous flower (g) epipetalous stamen Answer: a. Aestivation: The mode of arrangement of sepals or petals; with respect to the other members of the same whorl is called aestivation. b. Placentation: The arrangement of ovules in the ovary is called placentation.

c. Actinomorphic: When a flower shows radial symmetry, it is called an actinomorphic flower, e.g. mustard, datura, chilli, etc. d. Zygomorphic: When a flower shows bilateral symmetry, it is called a zygomorphic flower, e.

In this case, the ovary is said to be superior, e.g. mustard, China rose, brinjal, etc. f.

22 c. Actinomorphic: When a flower shows radial symmetry, it is called an actinomorphic flower, e.g. mustard, datura, chilli, etc. d. Zygomorphic: When a flower shows bilateral symmetry, it is called a zygomorphic flower, e.g. pea, gulmohar, bean, Cassia, etc. e. Superior Ovary or Hypogynous Flower: When the ovary occupies the highest position and other floral parts are below it, the flower is called hypogynous. In this case, the ovary is said to be superior, e.g. mustard, China rose, brinjal, etc. f. Perigynous Flower: When the ovary and other parts of the flower are situated at the same level, the flower is called perigynous. In this case, the ovary is said to be half-inferior, e.g. plum, rose, peach, etc. g. Epipetalous Stamens: When stamens are attached to the petals, this arrangement is called epipetalous, e.g. brinjal. Question 6. Differentiate between (a) Racemose and cymose inflorescence Answer: (b) Fibrous root and adventitious root Answer: (c) Apocarpous and syncarpous ovary

23 Answer: Carpels are free in apocarpous ovary, while they are fused in syncarpous ovary. Question 7. Describe modifications of stem with suitable examples. Answer: Modifications of Stem Modification for food storage: The underground stems of potato, ginger, turmeric, zamikand, Colocasia, etc. are modified for food storage. Such modifications are the tools of perenation to tide over unfavourable conditions. Modifications for climbing: In some plants, stem tendrils develop form axillary buds. These are slender and spirally coiled structures. A tendril helps the plant to climb to a support, e.g. cucumber, pumpkin, grapevine, etc. Modification for defence: In some plants, the axillary buds are modified into woody, straight and pointed thorns. Such thorns protect the plant from browsing animals, e.g. Citrus, Bougainvillea. Modification for photosynthesis: In some plants of arid regions, the stems are modified into flattened or fleshy cylindrical structures. The flattened structure can be seen in Opuntia and the cylindrical structure can be seen in Euphorbia. Such structures contain chlorophyll and photosynthesis happens in them. Modification for vegetative propagation: Stems are modified for vegetative propagation in many plants, e.g. grass, berry, dahlia, etc. Question 8. What is a flower? Describe the parts of a typical angiosperm flower. Answer: The flower is a reproductive part of an agiospermic plant. The flower serves the purpose of sexual reproduction. In a typical flower, there are four kinds of whorls. These whorls are successively arranged on the swollen end of the stalk or pedicel. The swollen end of the stalk is called thalamus or receptacle. Whorls of Flower: Calyx: The outermost whorl of a flower is called calyx. It is composed of sepals. Sepals are usually green and leaf-like structures. The sepals protect the flower during the bud stage. Calyx is called gamosepalous when sepals are united and is called polysepalous when sepals are free. Corolla: The second whorl of a flower is called corolla. It is composed of petals. Petals are usually brightly coloured. The bright colours attract the insects and birds for pollination. Corolla is called gamopetalous when petals are united and is called polypetalous when petals are free. Corolla can be tubular, bell-shaped, funnel-shaped or wheel-shaped.

24 Androecium: The third whorl of a flower is called androecium. It is composed of stamens. A stamen is composed of a stalk and an anther. An anther is usually a bilobed structure. There are two chambers (pollen sacs) in each lobe of an anther. Pollen sacs produce pollen grains. A sterile stamen is called staminode. Gynoecium: The central whorl of a flower is called gynoecium. It is composed of one or more carpels. A carpel is composed of three parts. The basal swollen portion is called ovary. The long tubular part over ovary is called style and the flat top at the style is called stigma. The style is the receptive surface for pollen grains. Each ovary bears one or more ovules which are attached to a flattened, cushion-like placenta. Question 9. How do the various leaf modifications help plants? Answer: Modification of Leaves Tendrils: In some plants, leaves are modified into tendrils to assist in climbing, e.g. pea. Spines: In some plants, leaves are modified into spines for defence, e.g. cactus. The leaf spine in cacti and in some other xerophytes also helps in reducing water loss by preventing transpiration. Bulb: In some plants, the leaves are modified into bulb for food storage, e.g. garlic and onion.

1. What is meant by modification of root? What type of modification of root is found in the:

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 (a) Banyan tree - prop roots (b) Turnip - storage roots (c) Mangrove