Plant Morphology : Root, Stem, Leaves, Flower, Seed with Example

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Plant Morphology

Morphology (Plant Morphology) is the name given to the science that deals with the study of the form and structure of things. No matter which plant you take, the morphology of a flowering plant includes the roots, stem, leaves, flowers, and fruits.

Morphology – Study of External Structure.

Phytomorphology is the study of the physical form and external structure of plants. This is usually considered distinct from plant anatomy, which is the study of the internal structure of plants, especially at the microscopic level. Plant morphology is useful in the visual identification of plants. Recent studies in molecular biology started to investigate the molecular processes involved in determining the conservation and diversification of plant morphologies. In these studies transcriptome conservation patterns were found to mark crucial ontogenetic transitions during the plant life cycle which may result in evolutionary constraints limiting diversification.

ROOT

Direct elongation of radicle.

Taproot – Primary roots and their branched constitute tap root. E.g., the Mustard plant

Fibrous root – When the Primary root is short lined and replaced by a large number of roots that originate from the base of the stem. E.g., Wheat plant

Adventitious root – Roots arise from another part. E.g.- Grass, Monstera, Banyan.

Functions – Absorption of water and mineral, provide proper anchorage, store reserve food material.

Region of root –

Root cap – covered by thimble-like structure at apex, protects tender apex.
Meristematic – few mm above root cap, small, thin-walled cells with dense protoplasm, divide repeatedly.
Elongation – Cells undergo rapid elongation & enlargement, length growth.
Maturation – Mature cells of elongation. Root hairs (fine, delicate, thread-like structure) are (+).

Modification of root –

Storage – Taproot- (Carrot, turnip), Adventitious (sweet potato) swell and store food.
Prop root -Roots become hanging structures to support the tree. E.g., Banyan tree
Stilt root – Supporting roots coming out of lower nodes of the stem. E.g.-Maize, Sugarcane
Pneumatophore – Roots come out of the ground and grow vertically, help to get O2. E.g., Rhizophora. (In swampy areas)

STEM

Ascending part of an axis bearing branches, leaves, flowers, develops from the plumule of the Embryo of germinating seed, beard Nodes – leaves are born. A portion between two nodes – Internodes, conducts water, minerals, photosynthesis.

Modification of stem-

Storage – Underground stems of potato, ginger, Zaminkant, Colocasia, act as organs of perennation to overcome the unfavourable condition.

Some plants in arid regions modify stem into a flattened or fleshy cylindrical structure.

Mint and jasmine, lateral branches arise from the base of the main axis.

Tendrils- Develop from axillary buds, slender, spirally coiled, help plant to the coil. E.g., Gourds (cucumber, pumpkin) & Grapevines.

Thorns – Axillary bud into woody, straight, pointed thorns. E.g., Citrus, Bougainvillea, protect from browsing animals.

Runners – Grows parallel to the horizon, from nodes new branches & root arise. E.g., Grapes, Strawberry.

Suckers – Parallel to the surface of the water. E.g. – Pistia, Eichhornia. In branches, Pineapple, branches originate from basal & underground portions of the main stem, give rise to leafy shoots. E.g., Chrysanthemum.

LEAF

Lateral, generally flattened structure, develops at nodes.

Parts of leaf

Leaf base – Leaf is attached to stem, may bear two small lateral leaves like structure called Stipules. Pulvinus – in the leguminous plant, it is swollen.
Petiole – Allow leaf blade to flutter in the wind, cooling the leaf, fresh air.
Lamina – (leaf blade) – green expanded part with veins & veinlets. Veins provide rigidity to the leaf blade.
Midrib – Middle vein

Venation

Arrangement of vein & veinlets in lamina of leaf.

Reticulate – Veinlets form a network. E.g., Dicot
Parallel – Veins run parallel to each other within lamina. E.g.-Monocot

Types of leaves

(Bud – axile of petiole)

Simple – Incisions of lamina don’t touch midrib.
Compound – Incisions reach midrib breaking it inti leaflets.

Pinnately – No. of leaflets are present on common axis- rachis, represent midrib of the leaf. E.g., Neem

Palmately – Leaflets are attached at a common point (Tip of the petiole), E.g., Silk cotton.

Phyllotaxy

The pattern of arrangement of leaves on stem/branch.

Alternate – Single leaf arise at each node in an alternate manner. E.g., China rose, Sunflower, Mustard. Leaves are small & short-lived, E.g., Australian acacia. Calyx & corolla are not distinct – Perianth. E.g., Lily
Opposite – Pair of leaves arise at each node and lie opposite to each other. E.g., Calotropis, Guava.
Whorled – More than two leaves at a nod, form whorl. E.g., Alstonia

Modification of leaves–

Tendrils – For climbing. E.g., Peas
Spines – Defense, E.g.- Cacti
Bulb – Store food. E.g., Onion, Garlic
Insectivorous – Trap insect. E.g., Pitcher plant, Venus flytrap. In Australian acacia, leaves are small, short-lived.

INFLORESCENCE

Arrangement of flowers on the floral axis.

When the shoot tip transforms into a flower – it is solitary (alone)

Racemose – Main axis continues to grow, and flowers are in acropetal succession.
Cymose – Main axis terminates in flower, basipetal order, limited growth.

FLOWER

Reproductive unit of angiosperms, four whorls are arranged on the swollen end of stalk/pedicel- thalamus/receptacle.

Types of flowers

1. Sex-Bisexual – Has both androecium & Gynoecium

Unisexual – Either only stamen or only carpels

2. Symmetry-

Actinomorphic – Can be divided in half in any plane (radial)

E.g.- Mustard, Datura, Chili

Zygomorphic – Two similar half by only one plane(bilateral). E.g., Pea, Bean

Asymmetric – Can’t be divided in half in any plane. E.g., Canna

3. Floral appendages –

Trimerous – Floral appendages are multiple of 3.

Tetramerous – Multiple of 4

Pentamerous – Multiple of 5

4. Bracts – (Reduced leaf found at the base of pedicel)

Bracteate – With bract

A-bracteate – Without bract

5. Position of Calyx, corolla & androecium with respect to the ovary on the thalamus

Hypogynous – Gynoecium occupies the highest position while others are situated below it. (Ovary superior). E.g.- Mustard, China rose, Brinjal

Perigynous – Gynoecium in the centre and other on the rim of the thalamus, same level (half inferior ovary). E.g., Plum, rose, peach.

Epigynous – Thalamus grows upward, enclosing ovary and fuses with it, other parts above the ovary (ovary inferior). E.g., Guava, Cucumber, Sunflower

Parts of Flower

(Calyx, corolla, Gynoecium, androecium)

Calyx + corolla – accessory organ.

Androecium + Gynoecium- Reproductive organ

Perianth – In lily, Calyx and corolla are not distinct.

Calyx – Outermost whorl, members – sepals (green, leaf-like, protect bud), can be gamosepalous (united sepals), Polysepalous (free sepals).
Corolla – Petals (bright colour to attract insects for pollination).

Gamopetalous (united petal), polypetalous (free petals) may be tubular, bell-shaped, wheel-shaped.

AESTIVATION- Arrangement of sepals/Petals in the floral bud with respect to others whorl.

Valvate – Sepals & petals just touch each other at the margin, without overlapping. E.g., Calotropis

Twisted – Overlap the next one and so. E.g., China rose, Lady’s finger.

Imbricate – Overlap but not in particular derivation (1 out, 1 in, three out-in).

Vexillary – Largest overlap two lateral petals which overlap two smallest one. E.g., Pea & Bean

Androecium – Composed of stamen (male reproductive organ)

Each has stalk/filament & another.

Each anther is bilobed (each has 2 chambers, pollen sacs).

Pollen grains are produced in pollen sacs.

Sterile stamen – Staminode.

Epipetalous – Stamen attached to petals, e.g.- Brinjal

Epiphyllous – Attached to the perianth. E.g., Lily-

Polyandrous – Remain free

United – together

Monadelphous – United into one bunch/bundle. E.g., China rose

Diadelphous – Two bundles. E.g., Pea

Polyadelphous – More than two. E.g., Citrus

There may be variation in the length of the filament within the flower. E.G.- Salvia and Mustard.

Gynoecium – Female reproductive part, made of one or more carpels.

Ovary- Enlarged basal part. Stigma – usually at the tip. Style – Connects ovary to stigma, receptive surface for pollen grains. Each ovary has One or more ovules attached to a cushion-like placenta.

Apocarpous- Where one or more carpel is (+), maybe free. E.g., Lotus, Rose.

Syncarpous – Carpel fuse. E.g., Mustard, tomato.

PLACENTATION – Arrangement of ovule within the ovary.

Marginal – Placenta forms ridge along ventral suture of ovary and ovule are born forming two rows. E.g., Pea

Axile – Placenta is axile; ovules are attached to the multilocular ovary.

E.g., China Rose, Tomato, Lemon

Parietal – Ovule on the inner wall of the ovary, which is one chamber but becomes two chambers because of a false septum. E.g., Mustard, argemone.

Free central – Ovule on Central axis, septa absent. E.g.- Dianthus, Primrose.

Basal – Placenta at base of ovary & single ovule is attached. E.g., Marigold, Sunflower

FRUIT

Mature or ripened ovary, develops after fertilization.

Parthenocarpic – formed without fertilization

Parts of Fruit

Pericarp – Wall of fruit, maybe dry/fleshy, when thick divided – Epicarp (outer), mesocarp (Middle), Endocarp (Inner).

In Mango & coconut, fruit – Drupes (develop from monocarpellary superior ovaries & one-seeded).

Mango – Thin epicarp, fleshy edible mesocarp, stony hard endocarp.
Coconut – Mesocarp- fibrous.

SEED

Ovule after fertilization, has seed coat & Embryo.

Embryo – Radicle, embryonal axis, one or more cotyledon. E.g., one – Wheat, maize, two – Gram pea.

Dicot seed – E.g., Gram, Pea

Seed Coat – Outermost covering, has two layers (outer Testa & inner tegmen)
Hilum – Scar on seed coat through which developing seeds were attached to the fruit, has small pore – micropyle.
Cotyledons – Often fresh, full of reserve food material

Endospermic seed – Endosperm formed as double fertilization, food stores.

Non – endospermic seed – Endosperm absence. E.g., Bean, Gram, Pea.

Monocot seed-E.g.- e.g., Wheat, Maize.

Mainly endospermic, orchids – non-endospermic.
In cereals(maize), the seed coat is membranous & fused with fruit wall, endosperm – bulky, stores food.
Aleurone layer – Proteinous outer covering of endosperm, separate Embryo. The Embryo is small & situated in a groove at one end.
Scutellum – Consists of one layer and shield-shaped cotyledon.
Coleoptile – Encloses plumule
Coleorhiza – Encloses radicle.

Semi technical description-

Br- Bracteate, K – Calyx, C – Corolla, P – Perianth, G for Superior ovary,

Fusion is indicated by enclosing figures within brackets.

The position of the mother axis with respect to the flower is represented by a dot on top.

Click Here for Complete Biology Notes

Description of important families –

Fabaceae

Earlier Papilionoideae (a subfamily of Leguminosae)

Vegetative character – Trees, shrubs, root with root nodules -stem, leaf – alternate, pinnately compound, leaf base, reticulate.
Floral –

– Inflorescence – Racemose

– Flower – bisexual, Zygomorphic

-Calyx – 5 sepals, gamosepalous, valvate/imbricate aestivation

-Corolla – 5 Petals, polypetalous, two lateral wings, 2 anterior, 1 posterior, vaxillary.

-Androecium – 10, diadelphous, anther dithecous

– Gynoecium -Ovary superior, Monocarpellary, unilocular, single style

-Fruit – Legume, non – endospermic

– Economic importance – Sources of pulses (arher, moong), Oil (groundnut), Fiber (sun hemp), Dye (Indigofera), fodder (Sesbania, Trifolium), Ornamental (Lupin, sweet pea), Medicine (mulaithi)

Solanaceae

Potato family

Vegetative – Herbs, Shrubs, rarely small

Stem – Rarely woody, Arial, erect, branched

Leaves – alternate, simple, reticulate

Floral –

-Inflorescence – Solitary, Cymose.

– Flower – Bisexual, actinomorphic

-Calyx – % sepals United, Valvate

-Corolla – 5 Petals, united, valvate

– Androecium – % stamen, Epipetalous

– Gynoecium – Bicarpellary, Syncarpous, ovary superior, bilocular, axile

-Fruit – berry/ capsule

-Seed – many endosperms

-Economic importance – Source of food (tomato, brinjal), spice, medicine (Belladonna, Ashwagandha), ornamentals, fumigator(tobacco)

Liliaceae

Lily family, Monocot

Vegetative – Herbs with underground bulbs
Leaves – mostly basal, alternate, liner
Floral –

– Inflorescence – cymose

-Flower – Bisexual, actinomorphic.

-Androecium – 6 Stamen, 3+3, epipetalous

-Perianth – 6 tepals (3+3) often united, velvet

-Gynoecium – Tricarpellary, Syncarpous, ovary superior, trilocular, axile

-Fruit – Capsule

– Seed – Endodermous

– Economic importance – good ornamentals (Tulip, Gloriosa), medicines (aloe), vegetables (Asparagus), Colchicine).

Floral Symbols

Floral formulae are used to describe a flower using some signs and symbols to designate different parts of a flower. Some of the different symbols used are as follows:

Symbol	Description / Full form
Br	Bracteate condition
Ebr	Ebracteate condition
Brl	Bracteolate
Epik	Epicalyx
Ebrl	Ebracteolate
0 (zero)	Absence of a particular whorl
∞	Indefinite number of floral parts in a whorl
⊕	Actinomorphic condition
%	Zygomorphic condition
K	Calyx (Sepals)
C	Corolla (petals)
P	Perianth (tepals)
A	Androecium (stamens)
G	Gynoecium (carpels)
⚥	Bisexual flower
⚦	Unisexual, staminate flower
♀️	Unisexual, pistillate flower
K₅	Five sepals, aposepalous
K₍₅₎	Five sepals gamosepalous
C₅	Five petals, apopetalous
C₍₅₎	Five petals, gamopetalous
	Epiphyllous stamens
	Epipetalous stamens
A₃	Three stamens free
A₂₊₂	Stamens 4, 2 whorls
A₁₀₊₁	Stamens 10, diadelphous – 9 stamens unite to form one bundle and 1 other bundle
A⁰	Sterile stamen (staminode)
G₀	Sterile carpel (pistillode)
G-	Semi inferior ovary
	Inferior ovary
	Superior ovary

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