MORPHOLOGY

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MORPHOLOGY :

MORPHOLOGY

Morphology :

Morphology Study deals with the forms and features of different plant organs such as roots, stems, leaves, flowers, seeds and fruits. The study of the external structures of organs is otherwise known as external morphology and that of internal structures as internal morphology.

Study of morpholgy:

Study of morpholgy Root, seed, stem, leaf, bark, wood, flower and fruit. Modification of root and stem and histology of dicot and monocot root, stem and leaf. All the morphological parts have their specific macroscopical and anatomical features which provides immense information regarding authenticity or otherwise adulteration.

MORPHOLOGY OF ROOT:

MORPHOLOGY OF ROOT

Definition :

Definition Root is the descending portion of the axis of the plant. It is not normally green in color. It is characterized by the absence of nodes and internodes.

Types of root system:

Types of root system

Tap Root System:

Tap Root System In dicots the radicle elongates into the primary root which grows downwards into the soil and bears smaller roots as its branches. The primary root grows and becomes the main root or the tap root. The tap root, along with its branches, constitutes the tap root system of a plant. As the primary root elongates, it goes on producing lateral branches called secondary roots. These in turn produce tertiary roots, which grow in various directions fixing the plant firmly into the soil.

Adventitious Root System:

Adventitious Root System Roots developing from any part of the plant body other than the radicle are called adventitious roots. They may arise from the leaves as in Bryophyllum or from the branches as seen in Banyan. In monocotyledons, the primary root from the radicle later disorganizes and a cluster of adventitious roots arise from the basal portion of the stem. They are of uniform thickness and length. In grasses and some herbaceous monocots, they look like tufts of fibres and are called fibrous roots. Fibrous roots are also adventitious.

Types of root system:

Types of root system Tap root system Adventitious root system

Regions of root:

Regions of root

Regions of root:

Regions of root

Functions of Roots:

Functions of Roots

Root Modifications:

Root Modifications Taproot and adventitious roots may undergo certain modifications to perform the function of storage and vegetative propagation.

Slide 16:

Fusiform root - In radish the modified tap root is thickened in the middle and tapers towards both ends. e.g., Raphanussativus (Radish) Napiform root - In beetroot the modified tap root is greatly swollen at the base, but abruptly narrows into a tail-like portion. e.g., Beta vulgaris (Beetroot) Conical root - In carrot the modified tap root is conical. It is broad at the base and gradually tapers towards its apex. e.g., Daucascarota (carrot)

Tap root modification for storage of food:

Tap root modification for storage of food

Tap root modification:

Tap root modification

Branch root modification:

Branch root modification For respiration Plants growing in marshy places & salt lakes Develop special kind of roots for breathing called ‘ pneumatophores’ or ‘respiratory’ or breathing roots. The breathing roots are vertically upwards and come out of the water like conical spikes around the tress. The breathing roots are provided with numerous pores toward the upper end, called ‘lenticels’. E.g. mangrove plant.

Branch root modification:

Branch root modification

Adventitious root modification-for storage of food:

Adventitious root modification-for storage of food

Adventitious root modification-for storage of food:

Adventitious root modification-for storage of food

Adventitious root modification-for mechanical support:

Adventitious root modification-for mechanical support

Adventitious root modification-for mechanical support:

Adventitious root modification-for mechanical support

Adventitious root modification-for vital functions:

Adventitious root modification-for vital functions

MORPHOLOGY OF STEM:

MORPHOLOGY OF STEM

DEFINITION:

DEFINITION Shoot is the ascending portion of the axis and develops from the plumule of the embryo. It consists of the main axis or stem, branches and leaves. The stem is provided with nodes and internodes which may not be distinct in all cases. Leaves and branches develop from the nodes. The portion between two successive nodes is called an internode . The terminal or apical bud lies at the apex of the stem whereas the axillary bud is present in the axil of a leaf and the stem.

Forms of stems :

Forms of stems

Duration of stem:

Duration of stem

Functions of stem:

Functions of stem The stem gives support to the branches and leaves. It helps in the upward conduction of water and mineral salts and downward conduction of prepared food material. When the plant matures, the stem and the branches take part in the formation of reproductive structures (flowers). The underground modified stems serve to store food materials. The underground stems and a few aerial stems take part in vegetative reproduction. photosynthesis

Aerial stem:

Aerial stem

Aerial stem:

Aerial stem

Weak stem:

Weak stem Trailers These are plants with a weak stem trailing on the ground without rooting at the nodes. Prostrate procumbent For the both, stem lies prostrate on the ground (e.g., Portulaca). decumbent the stem after trailing on the ground for some distance tends to rise at the apex (e.g. Tridax).

Weak stem:

Weak stem Creepers In some plants, the stem is weak and creeps on the surface of the soil. The creeping stem produces roots at the nodal regions (e.g. Oxalis).

Weak stem:

Weak stem Climbers In some plants the weak stem climbs on the neighbouring objects with some special devices. (e.g., Pea). Rootlet Climbers These climb with the help of aerial adventitious roots developed at the nodes, as in betel, pepper, Pothos and Ficusrepens. Hook Climbers In Bauhinia vahlii, the axillary buds get modified into curved watch-spring like hooks. With the help of these hooks, the plant is able to climb. In Artabotrys, hooks are found opposite the leaves. These hooks are modified peduncles or pedicels. Tendril Climbers Tendrils are slender, spirally coiled, spring like structures. They are highly sensitive to contact and coil around the neighbouring support. In Passiflora, the axillary bud instead of developing into a branch, gets transformed into a tendril. Leaf Climbers In Gloriosa, the tip of the leaf gets enlongated and serves as a tendril and the plant is hence called a leaf climber. Stem Climbers or Twiners These plants have long and slender stems with branches. They climb by twining bodily around trees and shrubs. (e.g., Ipomoea). Lianas These are woody perennial climbers, commonly seen in tropical forests. e.g., Entadaphaseoloides.

Branching of the stem:

Branching of the stem

Branching :

Branching Lateral Branching When the branches arise from the sides of the stem the branching is called Lateral. It is divisible into two types: Racemose or Monopodial or Indefinite Type Cymose or Definite Type

Lateral branching:

Lateral branching

Racemose or Monopodial or Indefinite Type:

Racemose or Monopodial or Indefinite Type e.g. Casurina, Polyalthia etc. Here the stem indefinitely grows by the terminal bud. The lateral branches of the main stem are arranged in an acropetal succession (produced successively towards the apex with older branches towards the base and younger ones towards the apex). As a result of this branching the plant appears conical or pyramidal in shape.

Cymose or Definite Type:

Cymose or Definite Type Here the growth of the main stem is definite. The main stem produces lateral branches which grow more vigorously than the main axis. As a result of this branching, the plant spreads out above and becomes more or less dome shaped. The cymose branching is of the following kinds. Uniparous Cyme A cymose type of branching with only one lateral branch produced at a time. It is also known as monochasial or sympodial . It shows two distinct types namely helicoid and scorpioid . In Saraca the branching is described helicoid . Here, the lateral branches develop on the same side forming a helix. In Vitisvinifera the branching is described as scorpioid . Here the lateral branches develop on alternate sides forming a zigzag. Biparous Cyme When two lateral branches, develop at a time the branching is said to be biparous or dichasial . Eg . Datura carissa . Multiparous Cyme When more than two branches develop at a time the branching is said to be multiparous or polychasial . Eg.Euphorbia , Croton bonplandianum .

Branching of stem:

Branching of stem cymose

Dichotomous Branching:

Dichotomous Branching In a few angiosperms, two branches are produced in forked manner, the branching are called dichotomous. E.g. riccia, screwpine.

Modification of stems:

Modification of stems

Slide 45:

In some plants the aerial stem is modified to perform a variety of special functions. The aerial stem modifications are as follows: Stem Tendril Tendrils develop as modifications of the stem in certain plants. The terminal bud gives rise to a tendril in Cissusquandrangularis and the axillary bud becomes modified into a tendirl in Passiflora . fig. 27.26 Auxillary Stem Tendrils of Passiflora Stem Thorn The thorn is a hard, straight, and pointed structure. In Bougainvillea and Duranta , the axillary bud is modified into a thorn. In Carissa the terminal bud is modified into a pair of thorns. The thorn sometimes bears leaves, flowers and fruits as seen in Duranta and Pomegranate. The thorns not only check the rate of transpiration but also protect the plants from herbivore grazing. Eg . Carissa, Duranta , Citrus fig. 27.27 Stem Thorns Thorns are small, modified stems, spines are modified superficial leaves and prickles are sharp, pointed structures without vascular tissue, arising on stem, petioles and inflorescence. Phylloclade A phylloclade is a flattened stem of several internodes functioning as a leaf. In Opuntia the stem is modified into a green flattened structure called Phylloclade. On the surface of the phylloclade, clusters of spines are formed. These spines are the modified leaves of the axillary bud. These spines not only check the rate of transpiration but also protect the plant from herbivores. The phylloclade has distinct nodes and internodes. E.g., Opuntia In Muehlenbeckia the stem is a thin, green, flat structure made up of nodes and internodes. Initially small normal leaves are formed but later only scale leaves. fig. 27.28 Phylloclade Cladodes and Cladophylls A phylloclade of one or two internode is called as a cladode. There are no suitable examples of cladodes because, Ruscus and Asparagus, which are often considered as cladodes, are in reality, cladophylls . A cladophyll is a flattened leaf like stem arising in the axils of a minute, bract-like, true leaf. fig. 27.29 - Cladodes Bulbil Bulbil is a speical multicellular body essentially meant for reproduction. In Agave the floral buds are modified into bulbils. These bulbils get detached, come in contact with the soil and develop into new plants. In Dioscorea the axillary bud develops into a bulbil . This bulbil detaches from the mother plant and grows up into a new independent one. fig. 27.30 Bulbil

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