MORPHOLOGY OF FLOWERING PLANTS :
THEORETICAL PARTS
1. INTRODUCTION TO MORPHOLOGY :-
- Plant morphology deals with the study of the physical form and external structure of plants
- . The underground part of the flowering plant is the root system while the portion above the ground forms the shoot system.
2. THE ROOT :-
- 2.1 Tap Root
- In the 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. Example- Mustard.
2.2 Fibrous root system :-
- These roots originate from the base of the stem and constitute the fibrous root system.
- Mostly seen in monocots. Example- Wheat
MORPHOLOGY OF FLOWERING PLANTS
2.3 Adventitious roots
- In some plants, roots arise from parts of the plant other than the radicle and are called adventitious roots.
- Example: Grass, Monstera and banyan tree.
2.4 Functions of Root
- Absorption of water and minerals from the soil
- Providing a proper anchorage to the plant parts
- Storing reserve food material
- Synthesis of plant growth regulators
MORPHOLOGY OF FLOWERING PLANTS
2.5 Regions of the Root
- 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.
- Region of meristematic activity:
- Cells of this region are very small, thin-walled and with dense protoplasm.
- They divide repeatedly.
- Region of elongation: Cells undergo rapid elongation and enlargement and are responsible for the growth of the root in length.
- Region of maturation:
- The cells of the elongation zone gradually differentiate and mature.
- From this region some of the epidermal cells form very fine and delicate, threadlike structures called root hairs.
- These root hairs absorb water and minerals from the soil.
3. MODIFICATIONS OF ROOT
3.1 Modified Tap Root For Storage Fusiform
- These roots are thicker in the middle and tapering on both ends
- Spindle-shaped appearance
- In this type of roots both hypocotyl and root help in storage of food
- Fine secondary roots arise from the apical part
- E.g. radish
3.2 Modified Tap Root For Storage: Conical Fusiform :
- These roots are thicker at their upper side and tapering at basal end
- Conical in shape
- Thread-like secondary roots present throughout
- Fleshy basal part is derived from the hypocotyl
- E.g. carrot
3.3 Modified Tap Root For Storage: Napiform :
- These roots become swollen and spherical at upper end and tapering like a thread at their lower end.
- E.g. beetroot, turnip
3.4 Modified Tap Root For Storage: Tuberous Root :
- Such roots do not have regular shape and get swollen and fleshy at any portion of roots
- E.g. Mirabilis jalapa
MORPHOLOGY OF FLOWERING PLANTS
3.5 Modified Tap Root For Storage: Nodulated Root :
- Secondary, tertiary or primary roots bear small nodule-like swellings Class 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- Swellings called as tubercles
- Contain nitrogen fixing bacteria
- Also called tuberculated roots
- Relationship: mutualistic symbiosis
- E.g. leguminous plants
3.6 Modified Tap Root For RESPIRATION: Respiratory Root :
- Found in plants growing in the mangroves or swamps; deficient in oxygen
- Possess horizontal cable roots which give rise to vertically upward aerial roots at short intervals
- Possess minute pores called pneumathodes or lenticels
- Also called pneumatophores.
- E.g. Rhizophora
3.7 Modified Adventitious Roots: Fasciculated Roots:
- Many adventitious roots are produced from one place forming a tuft or a cluster
- Also called fascicled roots
- E.g. Dahlia, Asparagus
3.8 Modified Adventitious Roots: Moniliform Roots:
- Adventitious roots swollen at regular intervals imparting bead-like appearance
- Also called beaded roots
- E.g. bitter gourd.
- Roots appear to be formed of a number of swollen discs placed one above the other giving a series of ring-like outgrowths or swellings.
- E.g. Psychotria,
- Roots are so thickened that they give the appearance of the palm of a hand
- E.g. Orchis,
- When the swelling in the roots is confined only near the tips
- E.g. turmeric.
MORPHOLOGY OF FLOWERING PLANTS
- When root arises obliquely from lower nodes and enter inside the soil and form a rope like structure
- Also called brace roots
- E.g. sugarcane, maize, sorghum.
- When root arises from branches of plant and grows downward towards soil function as supporting stem for the plant
- In the beginning these roots are aerial, hygroscopic and appear red in moistened state
- Also called pillar roots
- E.g. Ficus
3.14 Modified Adventitious Roots: Climbing Roots :
- These roots arise from nodes and/or internodes and help the plant in climbing
- They are non-absorptive or secrete a cementing gummy material
- Also called clinging roots
- E.g. Ficus pumila, money plant, Black pepper, Hedera helix
3.15 Modified Adventitious Roots: Assimilatory Roots :
- These roots are green and carry out photosynthesis
- Also called photosynthetic roots
- E.g. Tinospora, Trapa, Podostemon
3.16 Modified Adventitious Roots: Parasitic Roots :
- In parasitic plants, roots enter in the stem of host plant to absorb nutrition from host Class 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- Also called haustorial roots, sucking roots or suckers
- E.g. Cuscuta on Duranta, Viscum,
MORPHOLOGY OF FLOWERING PLANTS
3.17 Modified Adventitious Roots: Epiphytic Roots :
- Developed by epiphytes; the plants inhabiting the surface of other plants for shelter and space only: space parasites
- Roots are thick, irregular and hang in the air and develop from the stem
- Devoid of root cap and root hairs
- Outer covering of dead spongy tissue for water absorption from the atmosphere: velamen
- Roots also photosynthesize.
- Also called hygroscopic rootsClass 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- E.g. Vanda
3.18 Modified Adventitious Roots: Floating Roots :
- Some roots arising from the nodes of the hydrophytic plants become inflated, emerge out of the water, store air, make the plant buoyant and help in floating
- Also help in exchange of gases
- E.g. Pistia, Jussiaea .
3.19 Modified Adventitious Roots: Reproductive Roots :
- Fleshy adventitious roots that grow into new plants when detached under favourable conditions.
- E.g. Dahlia, Ipomoea .
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4 STEM :
4.1 General Information
- It develops from the plumule of the embryo of a germinating seed.
- The stem bears nodes and internodes.
- The main function of the stem is spreading out branches bearing leaves, flowers and fruits.
4.2 Modified Sub-Aerial Stems: RUNNER
- When stem grows and spread on the surface of soil. Roots are developed at lower side and leaves from upper side from node.
- E.g. Cynodon dactylon (Doob grass), Oxalis
4.3 Modified Sub-Aerial Stems: STOLON
- Elongated, horizontal lateral branch developing from the lower part of the man axis for some distance like an arch and then touching the ground to give rise to new shoot.Class 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- E.g. Fragaria (Wild strawberry), Jasminum, Peppermin
4.4 Modified Sub-Aerial Stems: OFFSET
- Short, only one internode long and thicker small runners bearing a cluster of leaves in rossette manner
- Adventitious roots arising from all nodes
- E.g. Pistia, Eichhornia
MORPHOLOGY OF FLOWERING PLANTS :
4.5 Modified Underground Stems: Sucker
- Non-green underground stem developing from an erect shoot
- Grows horizontally in the soil and then comes out to form a new shoot
- Shorter and stouter than an underground runner
- E.g. garden mint,Chrysanthemum
4.6 Modified Underground Stems: Rhizome
 |
- Rhizome is a modified underground stem.
- Stem is divided into nodes and internodes. Adventitious root on lower node.
- Example Ginger, Turmeric, Canna
MORPHOLOGY OF FLOWERING PLANTS :
4.7 Modified Underground Stems: Corm
- Short, thick, highly condensed, swollen, usually unbranched, spherical or sub spherical underground stem
- Produced annually and grows vertically in the soil
- E.g. Amorphophallus, Crocus, Colocasia
4.8 Modified Underground Stems: Bulb
- It is an underground pyriform-spherical structure that possesses a reduced convex or slightly conical disc-shaped stem.
- It stores food in scales, leaf base and bud.
- Example: Onion
4.9 Modified Underground Stems: Tuber
- Swollen underground stem developing at the growing tip of a branch (sucker or stolon) •
- Oval or spherical lacking adventitious roots and possessing a number of spirally arranged depressions called eyes
- E.g. Amorphophallus, Crocus, Colocasia
- Stem tendrils which develop from axillary buds, are slender and spirally coiled and help plants to climb such as in gourds (cucumber, pumpkins, watermelon) and grapevines
4.11 Modified Weak Aerial Stem: Thorns
- Axillary buds of stems may also get modified into woody, straight and pointed thorns.
- Thorns are found in many plants such as Citrus, Bougainvillea.
- They protect plants from browsing animal
4.12 Modified Erect Aerial Stems: Phylloclade
- Stem is modified into a flat, fleshy and green leaf like structure and carries out photosynthesis like leaf. •
- The leaves are modified into spines
- E.g. Opuntia, Euphorbia, Casuarina
4.13 Modified Erect Aerial Stems: Cladodes
- Typical phylloclade only one internode long
- Stem branches of limited growth and green
- True leaves reduced to scales or spines
- E.g. Ruscus, Asparagus
5. THE LEAF :
Leaf is a green, dissimilar exogenous lateral flattened outgrowth which is borne on the node of a stem or its branches is specialized to perform photosynthesis.
5.1 Types of Venations
- Reticulate- present in dicotyledons, there is a network of vein present, which are irregularly distributed.
- Parallel- present in monocotyledons, veins are parallel to each other.
5.2 Types of Leaves
- Simple- lamina is complete and incision doesn’t reach midrib
- Compound- incision touches midrib, that divides a leaf into a number of leaflets. Pinnately compound- the leaflets are present on common axis, i.e. midrib called the rachis
- Example: Neem.
- Palmately compound- leaflets are attached at the petiole tip, e.g. silk cotton
5.3 Phyllotaxy
- Pattern of arrangement of leaves around the stem
- Alternate type- single leaf present at each node, e.g. Hibiscus, Brassica.
- Opposite type- each node bears a pair of leaves, e.g. Psidium guajava, Calotropis.
- Whorled type- more than two leaves arise at the node to form a whorl, e.g. Alstonia.
5.4 Modifications of leaves
- Tendrils: a leaf modified to form long thread-like structure, it gives support to climbers, e.g. peas.
- Spine: In xerophytic plants to reduce water loss, e.g. cactus, aloe.
- For storage: e.g. garlic, onion.
- Phyllodes: petiole gets modified to form a leaf-like structure and function,
- e.g. Acacia.
- Pitcher in pitcher plant is a modified leaf which traps insect inside.
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iology morphology of flowering plants
6. THE FLOWER -
6.1 Introduction
- A flower has four whorls; calyx, corolla, androecium and gynoecium. These are attached to the swollen terminal of the pedicel called the thalamus.
6.2 Flower symmetry
- Actinomorphic- radially symmetrical flowers.
- e.g. chilli, datura, mustard.
- Zygomorphic- when a flower can be divided into two equal parts in only one vertical plane,
- e.g. canna
MORPHOLOGY OF FLOWERING PLANTS :
6.3 Flowers
- Flowers can be trimerous, tetramerous or pentamerous depending on the multiple of floral appendages present 3,4 or 5.
6.4 Types of Flowers
- Types of flowers depending on the presence or absence of bracts (reduced leaf present at the base of pedicel);
- Bracteate or Ebracteate
6.5 Types of flowers based on the position of the ovary
1. Hypogynous- gynoecium occupies the highest place, above all the other parts.
The ovary is known as superior, e.g. brinjal, china rose, mustard
2. Perigynous- gynoecium is present at the same level as the rest of the parts of a
flower. The ovary is known as half inferior e.g. peach, plum, rose
3. Epigynous- The thalamus encloses the ovary completely and other parts are
present above it. The ovary is known as inferior, e.g. ray florets of a sunflower,
guava, cucumber
MORPHOLOGY OF FLOWERING PLANTS :
6.6 Parts of a Flower
- Calyx: A flower’s outermost whorl is made up of leaf-like structures called sepals Gamosepalous- sepals united, Polysepalous- sepals free.
- Corolla: made up of bright coloured petals. Present after sepalsGamopetalous- petals united, Polypetalous- petal.
MORPHOLOGY OF FLOWERING PLANTS :
Aestivation Class 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- Valvate- sepals or petals just touch each other and don’t overlap in a whorl, e.g. Calotropis,
- Twisted- sepal or petal overlaps the next sepal or petal and the same continues in a whorl, e.g. cotton, china rose, lady’s finger.
- Imbricate- margins of sepal and petals overlap each other randomly and not in one direction, e.g. Gulmohar, Cassia.
- Vexillary- the largest petal overlaps two petals (wings) present laterally on both the sides and that overlaps the two anterior petals (keel) in the same way. It is also called papilionaceous, e.g. beans, peas
Androecium
- Androecium is composed of stamens.
- A sterile stamen is called staminode.
- When stamens are attached to the petals, they are epipetalous as in brinjal.
- Stamens when attached to the perianth as in the flowers of lily it is epiphyllous.
- Two bundles (diadelphous) as in pea.
- More than two bundles (polyadelphous) as in citrus.
- There may be a variation in the length of filaments within a flower, as in Salvia and mustard.
Gynoecium :
Class 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, morphology of flowering plants
- When carpels are free (as in lotus and rose). They are called apocarpous.
- Syncarpous when carpels are fused, as in mustard and tomato .
- Placentation: The specific arrangement of ovules in the ovary is called placentation. Types of placentation:
- Marginal- e.g. pea
- Axle- e.g. lemon, china rose
- Parietal- e.g. Argemone, mustard
- Free central- e.g. Primrose, Dianthus
- Basal- e.g. marigold, sunflower
7.INFLORESCENCE
- The arrangement of the flowers around the floral axis.
- The two main types of the inflorescence are:
- Racemose: the main axis grows indefinitely, flowers are present laterally in acropetal succession. Types- raceme, spike, umbel, capitulum, corymb, catkin, spadix, etc.
- Cymose: the main axis terminates in flower and has limited growth, flowers are borne in a basipetal order i.e. older flowers are at the top and new flowers are at the bottom
8. THE FRUITClass 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- It is a matured and ripened ovary after fertilisation.
- Parthenocarpic fruit: fruit formed without fertilisation, it makes seedless fruit, e.g. pineapple.
- Seed and pericarp make a fruit. The fleshy pericarp is made up of three layers; epicarp, mesocarp and endocarp
9. THE SEED
- After the fertilisation, the ovule develops into seed.
- A seed has a seed coat and an embryo. An embryo is made up of radicle, embryonal axis and one or two cotyledons in monocotyledons (maize, wheat) and dicotyledons (pea, gram) respectively.
Structure of a Dicotyledonous Seed
- The outermost covering of a seed is the seed coat.
- The seed coat has two layers, the outer testa and the inner tegmen.
- The hilum is a scar on the seed coat through which the developing seeds were attached to the fruit.
- Above the hilum is a small pore called the micropyle.
- Micropyle helps in absorbing the water at the time of germination of the seed.
- Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons.
- In some seeds such as castor the endosperm formed as a result of double fertilisation, is a food storing tissue.
- In plants such as bean, gram and pea, the endosperm is not present in mature seeds and such seeds are called non-endospermous.
MORPHOLOGY OF FLOWERING PLANTS :
10. STRUCTURE OF MONOCOTYLEDONOUS SEED
- Generally, monocotyledonous seeds are endospermic but some as in orchids are non-endospermic.
- The outer covering of endosperm separates the embryo by a proteinous layer called aleurone layer.
- The embryo is small and situated in a groove at one end of the endosperm.
- It consists of one large and shield shaped cotyledon known as scutellum and a short axis with a plumule and a radicle.
- The plumule and radicle are enclosed in sheaths which are called coleoptile and coleorhiza respectively.
11. FAMILY
11.1 Fabaceae
- This family was earlier called Papilonoideae, a subfamily of family Leguminosae.
- 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.
- Inflorescence: racemose
- Flower: bisexual, zygomorphic
- Calyx: sepals five, gamosepalous; 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 :
11.2 SolanaceaeClass 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
- It is a large family, commonly called as the ‘potato family’.
- Plants mostly, herbs, shrubs and small trees
- Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solidor hollow, hairy or glabrous, underground stem in potato (Solanum tuberosum)
- Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate
- 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 or capsule Seeds: many, endospermous
- Floral Formula:
11.3 Family Liliaceae
- Commonly known as Lily family.
- Perennial herbs with underground bulbs/corms/ rhizomes
- Leaves mostly basal, alternate, linear, exstipulate with parallel venation
- 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)
- Gynoecium: tricarpellary, syncarpous, ovary superior, trilocular with many ovules; axile placentation
- Fruit: capsule, rarely berry Seed: endospermous.
- Floral Formula: Class 11, Class 11biology notes, Class 11 Biology, Class 11 Biology chapter 1 , Class 11 Biology chapter 2, Class 11 Biology morphology of flowering plants
