Plant Morphology and Angiosperms

• Plant morphology deals with studying the forms and features of plant organs like roots, stems, leaves, and flowers, including their development.
• Angiosperms are flowering and fruit-bearing plants, appearing around 130 million years ago and comprising approximately 300,000 species, representing 50% of all plants.
• The smallest angiosperm is the rootless aquatic Wolffia, while the tallest is Eucalyptus, exceeding 100 meters.

Types of Flowering Plants

• Theophrastus classified plants based on shape and size, into herbs, shrubs, and trees.
• Herbs have soft stems and are small in size, for example, mustard and radish.
• Shrubs have woody stems, are of intermediate size, bushy, and perennial, for example, China rose and Croton.
• Trees are perennial, large in size, and have hard, woody branches.

Subtypes

• Culm is unbranched, jointed with distinct nodes and hollow internodes, e.g., Bambusa.
• Caudex has an unbranched trunk with a crown of terminal leaves, e.g., Areca catechu, Cocos nucifera, and palms.
• Excurrent is monopodial with one main stem or trunk, branches are acropetal and cone-like, e.g., Casuarina, Eucalyptus.
• Deliquescent has lateral branches and large suppression of the terminal bud, e.g., mango, Dalbergia, Ficus (banyan).

Lifespan Basis

• Annuals complete their life cycle within one season, producing seeds to survive unfavorable periods, e.g., mustard, wheat, sunflower, maize, and pea.
• Biennials complete their life cycle in two seasons, including vegetative and reproductive phases, e.g., turnip and carrot.
• Perennials survive for more than two years, flowering and fruiting during specific seasons, e.g., mango and Agave.

Flowering/Fruiting

• Monocarpic plants flower and fruit only once in their life, e.g., annuals, biennials, bamboo, and Agave.
• Polycarpic plants bear flowers and fruits repeatedly after maturity, e.g., mango, Acacia, Eucalyptus, etc.
• The angiospermic plant body includes the root, stem, leaves, flower, inflorescence, fruits, and seeds.

Root

• Roots are generally non-green, underground, positively geotropic (main root), positively hydrotropic, and often negatively phototropic, representing the descending and cylindrical axis of the plant body.
• The primary root develops from the radicle of the embryo, bearing lateral secondary roots that branch into tertiary roots, common in many dicot plants.
• A typical root consists of a root cap, a zone of meristematic activity, a region of cell elongation, and a zone of maturation with root hairs for water and mineral absorption.

Types of Root System

• Two primary root systems exist: tap root and adventitious root systems.
• Tap root systems consist of the primary root and its branches, common in dicot plants, e.g., mustard.
• Tap roots can be modified into fleshy structures, nodulated roots, or pneumatophores.

Tap Root Modifications

• Fleshy tap roots become swollen for food storage, mainly starch.
• Tuberous roots do not have a definite shape, swelling at any portion, e.g., Mirabilis, Trichosanthes.
• Napiform roots are thick at the base and taper towards the apex, e.g., turnip, sugar beet.
• Fusiform roots are thickest in the middle and taper at both ends, e.g., radish.
• Conical roots are swollen at the base and narrow at the apex, e.g., carrot.
• Pneumatophores are present in coastal plants, aiding respiration by absorbing oxygen, e.g., Rhizophora, Heritiera.
• Nodulated roots in leguminous plants form nodules with nitrogen-fixing bacteria for nitrogen fixation, e.g., Glycine max, gram, pea.

Adventitious Root

• Adventitious roots are roots produced from any part of the plant except the radicle, such as the hypocotyl, stem base, or nodes.
• Root hairs are found in the maturation region, absorbing water and minerals.

Adventitious Root Modifications

• Adventitious roots modify for food storage, mechanical support, and vital functions.

Fleshy Adventitious Roots

• Tuberous roots swell without defined shape, e.g., sweet potato.
• Fasciculated roots arise in bunches, e.g., Asparagus, Dahlia.
• Moniliform or beaded roots swell at intervals, e.g., Vitis.
• Nodulose roots have swollen apical portions, e.g., Curcuma.
• Annular roots form ring-like structures, e.g., Psychotria.

Mechanical Support

• Prop or pillar roots hang from branches, penetrating the soil, e.g., banyan, screwpine.
• Stilt or brace roots develop from lower stem nodes, providing additional support, e.g., maize, sugarcane.
• Climbing roots arise from nodes aiding in climbing, e.g., Pothos, Piper betle.

Vital Functions

• Buttress roots arise from the stem's base, e.g., Ficus.
• Contractile roots are underground and fleshy, aiding plant fixation, e.g., onion, corm of Crocus.
• Sucking or haustorial roots enter the host plant to absorb nutrition in parasitic plants, e.g., Cuscuta.
• Hygroscopic roots, found in epiphytes, hang freely absorbing moisture with velamen tissue, e.g., Orchid.
• Floating roots arise from nodes, aiding flotation, e.g., Jussiaea.
• Photosynthetic or assimilatory roots contain chlorophyll, e.g., Trapa, Tinospora.
• Reproductive roots develop vegetative buds, e.g., Trichosanthes dioica.
• Mycorrhizal roots have fungal hyphae, e.g., Pinus.
• Thorn roots serve as protective organs, e.g., Pothos.
• Clinging roots arise from nodes and penetrate host plants, e.g., Orchid, Ivy.
• Foliar roots arise from leaves, e.g., Bryophyllum.
• Mycorrhizae are symbiotic associations between plant roots and fungi, aiding nutrient absorption, particularly phosphorus and nitrogen.

Root Functions

• Roots anchor the plant in the ground
• Roots absorb water and minerals from the soil
• Roots store sugars produced during photosynthesis
• Roots transport water, minerals, sugars, and hormones to and from the shoot.
• Roots interact with soil fungi and microorganisms to acquire nutrients.

Specialized Root Functions

• Cortical cells in rice roots break down to form air spaces for gas exchange in flooded soils.
• Velamen, a thick, multilayered epidermis, covers epiphytic orchid roots, preventing water loss and aiding in water absorption.
• Root nodules in legumes and wattles contain nitrogen-fixing bacteria, converting atmospheric nitrogen into organic compounds available to the host plant.

Stem

• The stem is the ascending part of the plant axis bearing branches, leaves, flowers, and fruits.
• Develops from the plumule of the embryo, including nodes where leaves/buds arise and internodes. The stem bears nodes and internodes.

Special Stem Features

• Xerophytic plants: stems become green, flattened (phylloclade), or fleshy (cladophyll) for photosynthesis.
• Some plants have short, green cylindrical (e.g., Asparagus) or flattened (e.g., Ruscus) branches, develop from nodes of stem or branch in the axil of a leaf, limited in growth, specialized for photosynthesis (cladode).
• Some stems are thin, weak and lie prostrate on the soil.
• Tendrils are thread-like, green, leafless, spirally coiled structure that help weak stems climb.

Stem Modifications

• Classified based on structural and functional adaptations into underground/subterranean, aerial/epiterranean and sub-aerial/prostrate stems.

Underground Stems

• Modified for food storage and vegetative propagation.
• Bulb: reduced, disc-shaped stem with adventitious roots and scaly leaves.
• Rhizome: horizontal stem with nodes, internodes, buds, and scaly leaves for vegetative propagation.
• Corm: condensed, vertical structure with scale leaves.
• Tuber: swollen, bearing 'eyes'.

Aerial/Epiterranean Stems

• Stem tendril: apical bud modified into a tendril for climbing.
• Phylloclade: stem modified into a flat, fleshy, leaf-like structure.
• Stem thorn: axil of leaf or branch modified into a pointed thorn.
• Cladode: phylloclade consisting of one internode.
• Bulbil: multicellular structure for vegetative reproduction.

Sub-Aerial/Prostrate Stems

• Offset: short horizontal branch with leaves and roots.
• Stolon: grows upwards then arches down to form new plants.
• Runner: weak stem growing horizontally, developing roots at nodes.
• Sucker: grows horizontally underground and then upwards.

Stem function

• Support for leaves, branches, flowers, and fruits.
• Conducts water and minerals from roots to leaves, and synthesizes food from leaves to other plant parts.
• Secondary functions include storage, vegetative propagation and support.

Leaf structure

• A lateral, flattened structure borne on the stem, develops at the node and bears a bud in its axil.
• A typical leaf consists of a leaf base, petiole and lamina or leaf blade; some plants have lateral appendages (stipules).

Main parts

• Leaf base: by which leaf is attached to the stem
• Petiole: stalk of the leaf that connects the lamina with the stem
• Lamina or leaf blade: green expanded part of the leaf with veins and veinlets. In some leguminous plants, the leaf base may swell (pulvinus).

Venation

• Distribution of veins and veinlets in the lamina of leaf.

Types of Venation

• Reticulate venation: Veinlets form network, dicots
• Unicostate: Leaf has only one principal vein which extends from its base to apex, lateral branching forms network
• Multicostate: Several veins extend from base to apex and lateral veins form a network
• Parallel venation: veins arranged parallel to each other, monocots
• Unicostate: Leaf has only one main vein and lateral veins that run parallel
• Multicostate: Lamina possess several veins which run parallel

Leaf Types

• Based on lamina incision leaves are of two types: simple leaves with a single lamina, and compound leaves with incisions reaching the midrib or petiole.
• Based on origin and function leaves are classified as cotyledonary, prophylls bract, floral leaves foliage leaves and scaly leaves.

Phyllotaxy

• Patterns of leaf arrangement on the stem or branch, including alternate (single leaf at each node), opposite (two leaves at each node), and whorled (more than two leaves at a node) arrangements.
• Alternate phyllotaxy has a single leaf at each node, e.g., mango, China rose, mustard, tobacco.
• Opposite phyllotaxy has two leaves at each node, e.g., Calotropis, guava. It can be superimposed or decussate i.e. leaves of node are at right angles to the leaves of next node
• Whorled phyllotaxy has more than two leaves at a node, forming a whorl, e.g., Alstonia, Nerium, Vangueria.

Leaf Modifications

• Leaves adapt for functions beyond photosynthesis.
• Modifications include tendrils for support, spines for protection, and succulent leaves for water storage.
• Tendrils assist in climbing/support for weak stems.
• Spines prevent excessive transpiration.
• Succulent retain water

Some Modifications of Leaves

• Tendril (Green)
• Whole leaf tendril whose function is taken over by foliaceous stipules.
• Leaflet tendril (Only upper leaflets modified forming tendril).
• Stipular tendril (modification of stipules form tendril).
• Petiolar
• Leaf apex
• Spine prevent excessive transpiration.
• Succulent Leaves become fleshy and thickened

Foliar

• Leaves perform functions such as supporting and protection.
• Carry out photosynthesis and possess stomata
• Vascular bundles
• Storage, support and vegetative reproduction.

Inflorescence

• Arrangement of flowers on the floral axis
• The axis of the inflorescence is called the peduncle

Racemose Inflorescence

• Axis continues to grow with flowers laterally arranged with acropetal succession
• Classified into raceme, panicle, corymb, spike, spikelet, catkin, spadix, umbel, capitulum and capitate.
• Examples include mustard and radish.

Cymose

• Main axis ends in a flower, produces one lateral branch at a time ending in a flower.
• Included types are uniparous or monochasial cyme and biparous or dichasial cyme.

Racemose vs Cymose

Mixed Inflorescence

• Consists of cymose and racemose characters.
• Includes structures of racemes and cymes.
• Characterized by several character traits .
• includes Umbel/Thyrsus types

Special Inflorescence

• Cyathium: characteristic of Euphorbia, surrounded by male flowers and bracts.
• Hypanthodium: characteristic of family Moraceae and has a fleshy receptacle.
• Verticillaster: characteristic of tulsi (Ocimum)/ two cymose group.

Flower

• Flower is a modified condensed shoot of limited growth to carry out the function of reproduction in angiosperms.
• Calyx, corolla, androecium, and gynoecium are the four whorls of the flower
• These floral parts are stamen petal locule stigma style and ovule

Floral Symmetry

• Arrangement of floral appendages
• Asymmetric(eg. Canna): cannot be devided into two equal halves
• Actinomorphic(eg. mustard,chili): devided into two equal haves by vertical sections
• Zygomorphic (eg.pda bean,cassia): devided into two equal haves by two vertical section

Position of floral parts

• Hypogynous (eg.mustard)(superior): Ovary is situated at the top (stamens, petals and sepals below
• Perigynous (eg.rose, plum, peach): Ovary situated in the centre (other placed same lvl)
• Epigynous (eg.cucumber, guava): surrounded by the thalamus.

Number of floral parts

• Dimerous: parts in multiples of 2
• Trimerous: parts in multiple of 3
• Tetramerous: parts in multiple of 4
• Pentamerous : parts in multiple of 5.
• The structure of a flower consists of:
• non- essential and essential parts
• The partsof flower are as follow:
• Calyx, corolla Androecium,Gynoecium

Calyx or Sepal

• Outermost whorl
• Can either be polysepalous (free) or gamsepalaous(fused) as in Camopunulate
• Can undergo several modification
• sepal can become like spine or canbe tubular

Corolla/Petals

• Composed of petals and maybe be Gamopetalous or polypetalous
• Petals are brightly colored to attract insect
• Can be of different shapes like tubular

AESTIVATION

• Arragement of floral parts
• Valvate
• Twisted
• Imbricate

Androecium

• Third male whorl and collection of stamens
• Consists of stamen which has filaments/anther
• The anther can be either Dithecous/Monothevous

Gyandroeclum

• The innermost female whorl is composed of a carpal (Monocorpellary),or many carpels (polycarpellary)
• Comprises of Ovary/Style/Sigma
• Cohension.

Placentation

• Arrangment of ovules with the tissues: different types include;
• Marginal
• Axile
• parietal
• Free central
• Basal

Types of Fruits

Seed

• Seed us the fertilised ovules and consist of an embro
• The embryo has Radic/Embryonal axis

Floral Formula

• Used in describing various parts (roots,stems, leaves )
• Contains B,K,C,A
• +QBr , Ebr,and are all symbols used for the formula
• Q ,Br ,are also symbols

Vegetative Characters

• Family of Fabaceae :are trees/shrus,roots may have noodles
• Family of Solanaceae: are Herbs/Shrubs/Small trees,and stems maybe be herbatious
• Family of Liliaceae: Are perennial habs

Flower Factors

• Fabaceae: Flowers are bisexual,sepals fiive and more overries
• Solanaceae:Flower is bysexual,sepals fiive/ ovarries superior with manuy ovules
• Lilliceae:Flowers are 3 3 with tepallistis

An overview of plant morphology, including the study of plant organs like roots, stems, leaves, and flowers. Angiosperms, flowering and fruit-bearing plants, appeared about 130 million years ago. Classification by Theophrastus based on shape and size into subtypes like herbs, shrubs, and trees is also discussed.