Plants are an essential part of the ecosystem. Every life on the earth is directly or indirectly dependent on plants. Among the different parts of a plant, the leaf is the most essential.
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed.
Ginkgo is known as a Living Fossil.Anatomy of Ginkgo clearly shows primary and secondary structures. sex in Ginkgo is determined by sex chromosomes (XY in male and XX in female). Reproductive bodies of Ginkgo are most primitive among living seed plants except some Cycadales. Ginkgos are dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Female plants do not produce cones. Two ovules are formed at the end of a stalk, and after pollination, one or both develop into seeds. The fertilization of ginkgo seeds occurs via motile sperm, as in cycads, ferns, mosses and algae.
Stems of many plants are modified to perform different functions such as storage, protection, photosynthesis, support, propagation and perennation. Modifications help in better adaptation and survival.
Stems develop from the plumule of the germinating seed. It bears leaves, fruits, flowers, etc. The characteristic feature of a stem is nodes and internodes. The main function of the stem is to support other parts of the plant and conduction of food, water and minerals.
In some plants, stems are modified, which can be aerial, subaerial or underground modifications. They are modified to perform other functions, which are not normally associated with the stem.
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed.
Ginkgo is known as a Living Fossil.Anatomy of Ginkgo clearly shows primary and secondary structures. sex in Ginkgo is determined by sex chromosomes (XY in male and XX in female). Reproductive bodies of Ginkgo are most primitive among living seed plants except some Cycadales. Ginkgos are dioecious, with separate sexes, some trees being female and others being male. Male plants produce small pollen cones with sporophylls, each bearing two microsporangia spirally arranged around a central axis. Female plants do not produce cones. Two ovules are formed at the end of a stalk, and after pollination, one or both develop into seeds. The fertilization of ginkgo seeds occurs via motile sperm, as in cycads, ferns, mosses and algae.
Stems of many plants are modified to perform different functions such as storage, protection, photosynthesis, support, propagation and perennation. Modifications help in better adaptation and survival.
Stems develop from the plumule of the germinating seed. It bears leaves, fruits, flowers, etc. The characteristic feature of a stem is nodes and internodes. The main function of the stem is to support other parts of the plant and conduction of food, water and minerals.
In some plants, stems are modified, which can be aerial, subaerial or underground modifications. They are modified to perform other functions, which are not normally associated with the stem.
Vascular Cambium & Seasonal activity & its Role in Stem & RootFatima Ramay
Vascular Cambium & Seasonal activity & its Role in Stem & Root:
The vascular cambium (pl. cambia or cambiums) is a lateral meristem in the vascular tissue of plants.
The vascular cambium is a cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth.
In Dicots:
The vascular cambium is in dicot stems and roots, located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards).
In Monocots:
Monocot stems, such as corn, palms and bamboos, do not have a vascular cambium and do not exhibit secondary growth by the production of concentric annual rings. They cannot increase in girth by adding lateral layers of cells as in conifers and woody dicots.
Cambium of some plants remains active for the entire period of their life, i.e., cambial cells divide and resulting cells mature to form xylem and phloem elements.
This type of seasonal activity usually found in the plants present in the tropical regions, and not all plants show cambial activity.
Percentage of ringless trees in the rain forests of;India : 75%Amazon : 43%Malaysia : 15%
In regions with definite seasonal climate; seasonal activity of cambium ceased with onset of unfavorable conditions; In Autumn, it enters the dormant state and lasts for the end of summer; In Spring, cambium again becomes active.
Duration of cambial activity is also affected by day-length, e.g., In Robinia pseudoacacia, cambium is dormant under short-day condition.
The cambium cells formed in circular in cross section from the beginning onwards.
The cambial ring is partially primary (fascicular cambium) and partially secondary (interfascicular cambium).
Periderm originates from the cortical cells (extra stelar in origin).
In Dicot stem, for mechanical support xylem is with comparatively smaller vessels, greater fibers and less parenchyma.
More amount of cork is produces for protection.
Lenticels on periderm are very prominent.
The cambial ring formed is wavy in the beginning and later becomes circular.
The cambium ring is completely secondary in origin.
Periderm originates from the pericycle (intra stelar in origin).
In Dicot root, xylem is with big thin walled vessels with few fibers and more parenchyma.
Less amount of cork is produced as root is underground.
Lenticels on periderm are not very prominent.
Pteridophytes are vascular plants and have leaves (known as fronds), roots and sometimes true stems, and tree ferns have full trunks. Examples include ferns, horsetails and club-mosses. Fronds in the largest species of ferns can reach some six metres in length!
Many ferns from tropical rain forests are epiphytes, which means they only grow on other plant species; their water comes from the damp air or from rainfall running down branches and tree trunks. There are also some purely aquatic ferns such as water fern or water velvet (Salvinia molesta) and mosquito ferns (Azolla species).
Pteridophytes do not have seeds or flowers either, instead they also reproduce via spores.
There are around 13,000 species of Pteridophytes.
Vascular Cambium & Seasonal activity & its Role in Stem & RootFatima Ramay
Vascular Cambium & Seasonal activity & its Role in Stem & Root:
The vascular cambium (pl. cambia or cambiums) is a lateral meristem in the vascular tissue of plants.
The vascular cambium is a cylindrical layer of cambium that runs through the stem of a plant that undergoes secondary growth.
In Dicots:
The vascular cambium is in dicot stems and roots, located between the xylem and the phloem in the stem and root of a vascular plant, and is the source of both the secondary xylem growth (inwards, towards the pith) and the secondary phloem growth (outwards).
In Monocots:
Monocot stems, such as corn, palms and bamboos, do not have a vascular cambium and do not exhibit secondary growth by the production of concentric annual rings. They cannot increase in girth by adding lateral layers of cells as in conifers and woody dicots.
Cambium of some plants remains active for the entire period of their life, i.e., cambial cells divide and resulting cells mature to form xylem and phloem elements.
This type of seasonal activity usually found in the plants present in the tropical regions, and not all plants show cambial activity.
Percentage of ringless trees in the rain forests of;India : 75%Amazon : 43%Malaysia : 15%
In regions with definite seasonal climate; seasonal activity of cambium ceased with onset of unfavorable conditions; In Autumn, it enters the dormant state and lasts for the end of summer; In Spring, cambium again becomes active.
Duration of cambial activity is also affected by day-length, e.g., In Robinia pseudoacacia, cambium is dormant under short-day condition.
The cambium cells formed in circular in cross section from the beginning onwards.
The cambial ring is partially primary (fascicular cambium) and partially secondary (interfascicular cambium).
Periderm originates from the cortical cells (extra stelar in origin).
In Dicot stem, for mechanical support xylem is with comparatively smaller vessels, greater fibers and less parenchyma.
More amount of cork is produces for protection.
Lenticels on periderm are very prominent.
The cambial ring formed is wavy in the beginning and later becomes circular.
The cambium ring is completely secondary in origin.
Periderm originates from the pericycle (intra stelar in origin).
In Dicot root, xylem is with big thin walled vessels with few fibers and more parenchyma.
Less amount of cork is produced as root is underground.
Lenticels on periderm are not very prominent.
Pteridophytes are vascular plants and have leaves (known as fronds), roots and sometimes true stems, and tree ferns have full trunks. Examples include ferns, horsetails and club-mosses. Fronds in the largest species of ferns can reach some six metres in length!
Many ferns from tropical rain forests are epiphytes, which means they only grow on other plant species; their water comes from the damp air or from rainfall running down branches and tree trunks. There are also some purely aquatic ferns such as water fern or water velvet (Salvinia molesta) and mosquito ferns (Azolla species).
Pteridophytes do not have seeds or flowers either, instead they also reproduce via spores.
There are around 13,000 species of Pteridophytes.
This is a three chapter review for the Agriculture Major Admission Test conducted by the College of Agriculture of Cavite State University, the topicsare: Plant Bilogy, Crop and Agriculture and basic Physiological processes of plants. Credits to all my sourceswhich include lecture notes from our faculty, online sources and books published in the Republic of the Philippines.
It discuss about the total morphology of a leaf. It explains leaf characters, size, types, shape, Base of Sessile Leaves, kinds, functions, leaf modifications types, Phyllotaxis types, leaf margin, apex, lamina and leaf structure in detail.
In botany · Fruits are the means by which flowering plants (also known as angiosperms) · In common language usage, "fruit" normally means the seed-associated
Rhynia is a single-species genus of Devonian vascular plants. Rhynia gwynne-vaughanii was the sporophyte generation of a vascular, axial, free-sporing diplohaplontic embryophytic land plant of the Early Devonian that had anatomical features more advanced than those of the bryophytes.
What is Meristematic Tissue? Carl Wilhelm von Nägeli coined the term “meristem.” Meristematic tissue contains undifferentiated cells, which are the building blocks of the specialized plant structures. Meristematic tissues contain living cells with varied shapes.
Morphology and modifications of roots.pptxmanoj Joshi
The plants that we see today is the result of billions of years of evolution. Today, plants cover almost 30 per cent of the total landmass and account for the 50 per cent of the plant’s productivity (generation of biomass). Plants fulfil many roles in the ecosystem. They are a source of food, nutrition, shelter, maintain the integrity of soil (by preventing erosion) and most importantly, they are the main source for balancing the oxygen level in the atmosphere.
Characteristic form or bodily appearance of an organism.
(The habit of the plant can be understood only if the plant is provided with roots or seen growing in
nature.)
In plants some structures are already present to defend the attack while in others, the structures to defend the host develops after the infection. In this way, structural defense can be characterized as
Classification denotes the arrangement of a single plant or group of plants an distinct category following a system of nomenclature, and in accordance with a particular and well established plan.
A collection of dried and pressed plant arranged according to a classification system and available for study or reference is known as herbarium ( plural herbaria).
Taxonomy (or systematics) is basically concerned with the classification of organisms. Living organisms are placed in groups on the basis of similarities and differences at the organismic, cellular, and molecular levels.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
2. • Plants are an essential part of the ecosystem. Every life
on the earth is directly or indirectly dependent on
plants. Among the different parts of a plant, the leaf is
the most essential.
• Primarily, leaves have two functions: photosynthesis
and transpiration. In some plants, it takes up the
responsibility of reproduction also.
3. Table of Contents
• Structure
• Types
• Modification
• Function
• Key Points
• Let’s learn more about the morphology of leaves, parts of a leaf, different
types of leaves and their modifications.
4. Structure of a Leaf
• Leaves are thin, flat organs responsible for photosynthesis in the plants. It develops laterally at the node. It is an important
part of the shoot system and it originates from shoot apical meristems.
• The structure of a leaf is described below in detail :
• Parts of a Leaf
• Generally, leaf base, petiole, and lamina, together form the main parts of a leaf.
• Leaf Base: This is the part where a leaf attaches to the stem. Leaf base has two small leaf-like structure called stipules. In
plants like paddy, wheat, and other monocotyledons, this leaf base is wide and masks the stem.
• Petiole: Petiole is the long, thin, stalk that links the leaf blade to the stem.
• Lamina: Also known as leaf blade. It is the green, flat surface of the leaves. It consists of a small branched vein and
veinlets. The vein that runs along the middle of the lamina is called midrib. Midrib divides the surface of the lamina into
two. These veins and veinlets give rigidity to the leaf blade and help in the transportation of water and other substances.
5. Venation
• Venation is defined as the arrangement of
veins and the veinlets in the leaves.
Different plants show different types of
venation. Generally, there are two types of
venation:
• Reticulate venation: In a reticulate
venation, the veinlets are randomly
arranged and form a complex network of
veinlets. Ex: Dicotyledonous plants like a
rose plant.
• Parallel venation: In a parallel venation,
the veinlets run parallel to each other. Ex:
In monocotyledons like paddy.
6. Types of Leaves
• There are two broad categories of leaves – simple and
compound, which are further classified into different groups
based on their shape, size, their arrangements on the
stem, leaves of flowering and non-flowering plants, and various
other physical attributes.
• The two different types of leaves found in a plant are:
• Simple Leaf
• When a single lamina is connected to the main stem by a petiole,
the leaf is said to be simple. A simple leaf may be incised to any
depth but not down to the midrib or petiole. Eg., Guava leaves
• Compound Leaf
• A compound leaf is a leaf made up of two or more leaflets. In a
compound leaf, the midrib of the leaf is branched into different
leaflets and is connected by a single petiole. For eg., Pea, palm
leaves.
8. Palmately
Compound Leaf
In a palmately compound leaf, the leaflets are attached at the
tip of the petiole. Eg., Silk cotton. These can be differentiated
into:
1.Unifoliate: These type of leaves have only one leaflet. Eg.,
Citrus
2.Bifoliate: These leaves have two leaflets. Eg., Balanites
3.Trifoliate: These leaves have three leaflets emerging from
the same point. Eg., Oxalis
4.Quadrifoliate: These leaves have four leaflets arising from
the same point. Eg., Marsilea
5.Multifoliate: This type of leaf has many leaflets arising at a
common pint. Eg., Bombax
14. Pinnately
Compound Leaf
• In a pinnately compound leaf, the midrib of the leaf is divided into numerous leaflets and all connected by a common
axis. Eg., Neem. These can be further differentiated into:
1. Pinnate: A compound leaf that has an axis on each side of the midrib is known as a pinnate leaf.
2. Unipinnate: The leaf with leaflets on each side of the axis. Eg., cassia
3. Bipinnate: Here, a secondary axis bearing the leaflet is produced by the central axis. Eg., Acacia
4. Tripinnate: Here, a tertiary axis bearing leaflets emerges from the secondary axis. Eg., Moringa
5. Decompound: Leaf with more than three pinnate. Eg., old leaves of coriander
6. Parapinnate: A leaf without a terminal leaflet. Eg., Cassia
7. Imparipinnate: Leaf with an odd terminal leaflet. Eg., Pea
22. Phyllotaxy
• The patterns of arrangement of leaves on the stem are called Phyllotaxy. Plants show three types of
phyllotaxy- alternate, opposite and whorled types of phyllotaxy.
• When only a single leaf develops at each node alternatively, it is an alternate type of phyllotaxy. E.g.
China rose.
• When a pair of leaves develops at each node opposite to each other, it is called opposite phyllotaxy.
E.g. Guava plants.
• When more than two leaves develop at the nodes to form a whorl of leaves, it is called whorled
phyllotaxy. E.g. Alstonia.
23. Modification Of Leaves
• We know leaves are specialised to perform photosynthesis. In addition, they also have other significant roles to play, such as support, storage
of food, defence, etc. For each of these functions, they have been modified into different forms.
• For example, tendrils of peas, spines of cacti, onion bulb, leaves of insectivorous plants, etc. are different modified leaves. Let us have a
detailed look at some of the modification of leaves:
• Storage Leaves
• The xerophytic plants and plants belonging to the Crassulaceae family have thick and succulent leaves that store water in their tissues. The
parenchymatous cells of these leaves have large vacuoles filled with hydrophilic colloid. This modification helps the plant to resist desiccation.
• Leaf Tendrils
• Leaf tendrils exist in plants with weak stems. The leaves get modified into thread-like structures called tendrils. These tendrils climb a nearby
stick or wall and provide support to the plant. For eg., In Lathyrus aphaca, the whole leaf is modified into tendrils. The upper leaflets of Pisum
sativum get modified into tendrils.
• Leaf Spines
• A few plants have their leaves modified into needle-like structures known as spines. The spines act as defensive structures. They also reduce
water loss due to transpiration. For eg., in Opuntia, the leaves are modified into spines.
27. • Scale Leaves
• These are thin, membranous structures, without stalks, brownish or colourless in
appearance. They protect the auxiliary bud present in their axil. Scale leaves in onion are
fleshy and thick and store food and water. Casuarina and Asparagus also contain sale
leaves
• Leaflet Hooks
• In some plants, the terminal leaflets of leaf get modified into hook-like structures that help
them in climbing. Eg., Bignonia unguiscati.
• Leaf Roots
• In a few plants, one of the leaves present at the nodes gets modified into adventitious roots
which helps them to float over the water surface. Eg., Salvinia
• Phyllode
• In some plants, the petiole becomes flattened, taking the shape of a leaf and turns green in
colour. This is known as phyllode. For eg., Australian Acacia.
32. Insectivorous Leaves
• Few plants require nitrogen for their development. In such plants, the leaves are modified to catch and digest insects. Few of
the modifications are mentioned below:
• Leaf Pitcher- In a few plants like Nepenthes, the leaf-lamina is modified into a pitcher-like structure. The insect is digested into
the inner walls of the pitcher which secretes a digestive fluid into the pitcher cavity.
• Leaf Bladder- In such plants, the segments of the leaves are modified into bladders. These plants are found in water. The
inner wall is provided with digestive glands which helps in digesting the trapped insect. For eg., Utricularia
• In Drosera– The lamina possesses numerous hair with a sticky globule at its tip containing digestive enzymes. The moment an
insect sits on the lamina, the hair covers the insect completely.
36. Functions of Leaves
• The leaves perform the following functions:
• Photosynthesis is the primary function of leaves. They convert carbon dioxide, water, and UV light into glucose through the process
of photosynthesis.
• Transpiration is the removal of excess water from the plants into the atmosphere. This occurs by the opening of stomata present in
the leaves.
• Guttation Removal of excess water from the xylem at the edges of the leaves when the stomata are closed is known as guttation.
• Storage Leaves are a site of photosynthesis. Therefore, they store water and nutrients. The succulent and thick leaves particularly
adapt to water storage.
• Defense Some leaves are modified into spines to protect them from being damaged or eaten by animals. For eg., Opuntia.
37. Key Points
• Leaves are found at the nodes of the stem and contain the photosynthetic pigment chlorophyll.
• There are three main parts of a leaf – Leaf base, leaf lamina, and petiole.
• There are two different types of leaves – simples leaves and compound leaves. The other types of leaves include
acicular, linear, lanceolate, orbicular, elliptical, oblique, centric cordate, etc.
• They perform the function of photosynthesis and help in the removal of excess water from the aerial parts of the plant.
• They are modified in the form of spines, tendrils, hooks and scales and help them to adapt to various environments.
38. Frequently Asked Questions
What do you mean by the morphology of leaves?
Morphology is the study of science that deals with the form and structure of an organism. Morphology of leaves deals with the study of the structural
features and parts of a leaf.
What are the different types of leaves?
There are two different types of leaves – simple and compound leaves. Simple leaves are lobed or divided but do not form distinct leaflets. Whereas, in a
compound leaf the leaves are divided into distinct leaflets and each leaflet has a small petiole.
What is the most important function of the leaves?
Photosynthesis is the major function performed by leaves. They convert carbon dioxide, water and sunlight into glucose and energy.
How are the veins of the leaves important?
The veins of the leaves are provided with vascular tissues called xylem and phloem. Xylem transports water from the roots to the leaves whereas phloem
transports food through the leaf to rest of the plant.
Why are leaves a major part of the plant?
Leaves are the main source of photosynthesis, the process by which the plants feed themselves. They also help to transport water and food to different
parts of the plant. Thus they play a major role in the survival of a plant. Besides, they also help in the exchange of gases by the opening and closing of
stomata and removes excess water from the plant by the process of transpiration.
What are the different shapes of the leaves?
There are various types of leaves, each with its own shapes. These shapes range from oval, elliptical and linear, to truncate and lanceolate.
What is wilting?
Wilting is the drying out, withering and drooping of leaves of a plant due to insufficient water supply, excessive transpiration or some vascular disease.
What is the different modification of leaves?
Leaves can be modified in the form of spines that reduce water loss and also act as a defence. Some are modified into tendrils to provide support to the
plant. Some leaves are thick that help in water storage. Some are modified to catch and digest insects.