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1.4.11.10: Stems - Biology

1.4.11.10: Stems - Biology


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Learning Objectives

  • Describe the main function and basic structure of stems

Stems are a part of the shoot system of a plant. They may range in length from a few millimeters to hundreds of meters, and also vary in diameter, depending on the plant type. Stems are usually above ground, although the stems of some plants, such as the potato, also grow underground. Stems may be herbaceous (soft) or woody in nature. Their main function is to provide support to the plant, holding leaves, flowers and buds; in some cases, stems also store food for the plant. A stem may be unbranched, like that of a palm tree, or it may be highly branched, like that of a magnolia tree. The stem of the plant connects the roots to the leaves, helping to transport absorbed water and minerals to different parts of the plant. It also helps to transport the products of photosynthesis, namely sugars, from the leaves to the rest of the plant.

Plant stems, whether above or below ground, are characterized by the presence of nodes and internodes (Figure 1). Nodes are points of attachment for leaves, aerial roots, and flowers. The stem region between two nodes is called an internode. The stalk that extends from the stem to the base of the leaf is the petiole. An axillary bud is usually found in the axil—the area between the base of a leaf and the stem—where it can give rise to a branch or a flower. The apex (tip) of the shoot contains the apical meristem within the apical bud.

Stem Anatomy

The stem and other plant organs arise from the ground tissue, and are primarily made up of simple tissues formed from three types of cells: parenchyma, collenchyma, and sclerenchyma cells.

Parenchyma cells are the most common plant cells (Figure 2). They are found in the stem, the root, the inside of the leaf, and the pulp of the fruit. Parenchyma cells are responsible for metabolic functions, such as photosynthesis, and they help repair and heal wounds. Some parenchyma cells also store starch. In Figure 2, we see the central pith (greenish-blue, in the center) and peripheral cortex (narrow zone 3–5 cells thick just inside the epidermis); both are composed of parenchyma cells. Vascular tissue composed of xylem (red) and phloem tissue (green, between the xylem and cortex) surrounds the pith.

Collenchyma cells are elongated cells with unevenly thickened walls (Figure 3). They provide structural support, mainly to the stem and leaves. These cells are alive at maturity and are usually found below the epidermis. The “strings” of a celery stalk are an example of collenchyma cells.

Sclerenchyma cells also provide support to the plant, but unlike collenchyma cells, many of them are dead at maturity. There are two types of sclerenchyma cells: fibers and sclereids. Both types have secondary cell walls that are thickened with deposits of lignin, an organic compound that is a key component of wood. Fibers are long, slender cells; sclereids are smaller-sized. Sclereids give pears their gritty texture. Humans use sclerenchyma fibers to make linen and rope (Figure 4).

Practice Question

Which layers of the stem are made of parenchyma cells?

  1. cortex and pith
  2. phloem
  3. sclerenchyma
  4. xylem

[reveal-answer q=”700313″]Show Answer[/reveal-answer]
[hidden-answer a=”700313″]Answer a and b. The cortex, pith, and epidermis are made of parenchyma cells.[/hidden-answer]

Stem Modifications

Some plant species have modified stems that are especially suited to a particular habitat and environment (Figure 5). A rhizome is a modified stem that grows horizontally underground and has nodes and internodes. Vertical shoots may arise from the buds on the rhizome of some plants, such as ginger and ferns. Corms are similar to rhizomes, except they are more rounded and fleshy (such as in gladiolus). Corms contain stored food that enables some plants to survive the winter. Stolons are stems that run almost parallel to the ground, or just below the surface, and can give rise to new plants at the nodes. Runners are a type of stolon that runs above the ground and produces new clone plants at nodes at varying intervals: strawberries are an example. Tubers are modified stems that may store starch, as seen in the potato (Solanum sp.). Tubers arise as swollen ends of stolons, and contain many adventitious or unusual buds (familiar to us as the “eyes” on potatoes). A bulb, which functions as an underground storage unit, is a modification of a stem that has the appearance of enlarged fleshy leaves emerging from the stem or surrounding the base of the stem, as seen in the iris.

Watch botanist Wendy Hodgson, of Desert Botanical Garden in Phoenix, Arizona, explain how agave plants were cultivated for food hundreds of years ago in the Arizona desert in this video: Finding the Roots of an Ancient Crop.

A link to an interactive elements can be found at the bottom of this page.

Some aerial modifications of stems are tendrils and thorns (Figure 6). Tendrils are slender, twining strands that enable a plant (like a vine or pumpkin) to seek support by climbing on other surfaces. Thorns are modified branches appearing as sharp outgrowths that protect the plant; common examples include roses, Osage orange and devil’s walking stick.


Coronavirus disease 2019 (COVID�) is an acute respiratory infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS𠄌oV𠄂). COVID� mainly causes damage to the lung, as well as other organs and systems such as the hearts, the immune system and so on. Although the pathogenesis of COVID� has been fully elucidated, there is no specific therapy for the disease at present, and most treatments are limited to supportive care. Stem cell therapy may be a potential treatment for refractory and unmanageable pulmonary illnesses, which has shown some promising results in preclinical studies. In this review, we systematically summarize the pathogenic progression and potential mechanisms underlying stem cell therapy in COVID�, and registered COVID� clinical trials. Of all the stem cell therapies touted for COVID� treatment, mesenchymal stem cells (MSCs) or MSC‐like derivatives have been the most promising in preclinical studies and clinical trials so far. MSCs have been suggested to ameliorate the cytokine release syndrome (CRS) and protect alveolar epithelial cells by secreting many kinds of factors, demonstrating safety and possible efficacy in COVID� patients with acute respiratory distress syndrome (ARDS). However, considering the consistency and uniformity of stem cell quality cannot be quantified nor guaranteed at this point, more work remains to be done in the future.

The potential mechanisms of MSCs therapy for COVID�. MSCs have great therapeutic potential in immunomodulation and tissue repair through secretion of soluble paracrine protein factors and exosomes. MSCs can regulate the functions of a variety of immune cells, secrete several cytokines, promote tissue repair and regeneration, and may play important therapeutic roles in patients with COVID�. MSCs: mesenchymal stem cells HGF, hepatocyte growth factor VEGF, vascular endothelial growth factor KGF, keratinocyte growth factor FGF, fibroblast growth factor TGF‐β, transforming growth factor‐β TNF‐α, tumor necrosis factor‐α MSC𠄎xo, exosomes.


Question 1.
The cytoplasmic connections from cell to cell are known as
(a) middle lamella
(b) plasmodesmata
(c) cell membrane system
(d) endoplasmic reticulum

Question 2.
Bacterial flagella is made up of
(a) tubulin
(b) flagellin
(c) chitin
(d) None of these

Answer: (b) flagellin
Explanation:
Bacterial flagella is made up of protein flagellin.

Question 3.
Plasmolysis occurs due to-
(a) Absorption
(b) Endosmosis
(c) Osmosis
(d) Exosmosis

Question 4.
The term Cell was given by-
(a) Leeuwenhoek
(b) Robert hooke
(c) Flemming
(d) Robert Brown

Question 5.
Which one of the following also acts as a catalyst in a bacterial cell?
(a) 23 sr RNA
(b) 5 sr RNA
(c) sn RNA
(d) hn RNA

Question 6.
Centrosome is found in-
(a) Cytoplasm
(b) Nucleus
(c) Chromosomes
(d) Nucleolus

Question 7.
Plasma membrane is
(a) impermeable
(b) semi-permeable
(c) completely permeable
(d) differentially permeable

Answer: (b) semi-permeable
Explanation:
Plasma membrane is a selective permeable membrane that allows only selective molecules to pass through it.
The permeability depends on the electric charge and polarity of the molecules.

Question 8.
Middle lamella is made up of ___________.
(a) calcium sulphide
(b) calcium pectate
(c) calcium carbonate
(d) calcium chloride

Answer: (b) calcium pectate
Explanation:
Middle lamella is made up of calcium pectate.

Question 9.
Match the columns.
1. Cytoskeleton – A. hair-like outgrowth
2. Flagella – B. proximal region of centriole
3. Hub – C. bristle-like structures
4. Fimbriae – D. filamentous protein structure
(a) 1-D, 2-A, 3-B, 4-C
(b) 1-D, 2-C, 3-B, 4-A
(c) 1-B, 2-D, 3-A, 4-C
(d) 1-D, 2-A, 3-C, 4-B

Answer: (a) 1-D, 2-A, 3-B, 4-C
Explanation:
A filamentous protein structure present in the cytoplasm is called cytoskeleton.
Flagella is a hair-like outgrowths of the cell membrane.
The central part of the proximal region of the centriole is called hub.
Fimbriae are small bristle like fibres sprouting out of the cell.

Question 10.
Which of the following does not have cell wall?
(a) Mycoplasma
(b) Bacteria
(c) PPLO
(d) Blue green algae

Answer: (a) Mycoplasma
Explanation:
Mycoplasma does not have cell wall.
PPLO (Pleuro Pneumonia Like Organisms)

Question 11.
Centrosome is found in-
(a) Cytoplasm
(b) Nucleus
(c) Chromosomes
(d) Nucleolus

Question 12.
The longest cell in human body is
(a) red blood cells
(b) white blood cells
(c) columnar epithelial cells
(d) nerve cells

Answer: (d) nerve cells
Explanation:
Nerve cells are the longest cells.

Question 13.
The main site for synthesis of lipids is
(a) vacuoles
(b) RER
(c) SER
(d) Golgi body

Answer: (c) SER
Explanation:
The main site for synthesis of lipid is smooth endoplasmic reticulum.

Question 14.
The function of ribosomes is
(a) metabolism
(b) lipid synthesis
(c) protein synthesis
(d) photosynthesis

Answer: (c) protein synthesis
Explanation:
Ribosomes are called protein factories because they synthesize proteins.

Question 15.
Which is called Suicidal Bag?
(a) Centrosome
(b) Lysosome
(c) Mesosome
(d) Chromosome

Question 16.
A nucleosome is a portion of the chromonema containing ______.
(a) both DNA and histones
(b) only histones
(c) both DNA and RNA
(d) only DNA

Answer: (a) both DNA and histones

Question 17.
The largest cell in the human body is-
(a) Nerve cell
(b) Muscle cell
(c) Liver cell
(d) Kidney cell

Question 18.
Keeping in view the fluid mosaic model for the structure of cell membrane, which one of the following statements is correct with respect to the movement of lipids and proteins from one lipid monolayer to the other (described as flip-flop movement)?
(a) Neither lipids, nor proteins can flip-flop
(b) Both lipids and proteins can flip-flop
(c) While lipids can rarely flip-flop, proteins can not
(d) While proteins can flip-flop, lipids can not

Answer: (c) While lipids can rarely flip-flop, proteins can not

Question 19.
Cell secretion is done by-
(a) Plastids
(b) ER
(c) Golgi apparatus
(d) Nucleolus

Question 20.
___________ increases the surface area for mitochondrial activity.
(a) Inner membrane
(b) Inter membrane space
(c) Matrix
(d) Cristae

Answer: (d) Cristae
Explanation:
The inner membrane forms a number of foldings called cristae towards the matrix. These cristae increases the surface area.

We hope the given NCERT MCQ Questions for Class 11 Biology Chapter 8 Cell: The Unit of Life with Answers Pdf free download will help you. If you have any queries regarding CBSE Class 11 Biology Cell: The Unit of Life MCQs Multiple Choice Questions with Answers, drop a comment below and we will get back to you soon.


Essentials of Stem Cell Biology

First developed as an accessible abridgement of the successful Handbook of Stem Cells, Essentials of Stem Cell Biology serves the needs of the evolving population of scientists, researchers, practitioners, and students embracing the latest advances in stem cells. Representing the combined effort of 7 editors and more than 200 scholars and scientists whose pioneering work has defined our understanding of stem cells, this book combines the prerequisites for a general understanding of adult and embryonic stem cells with a presentation by the world's experts of the latest research information about specific organ systems. From basic biology/mechanisms, early development, ectoderm, mesoderm, endoderm, and methods to the application of stem cells to specific human diseases, regulation and ethics, and patient perspectives, no topic in the field of stem cells is left uncovered.

First developed as an accessible abridgement of the successful Handbook of Stem Cells, Essentials of Stem Cell Biology serves the needs of the evolving population of scientists, researchers, practitioners, and students embracing the latest advances in stem cells. Representing the combined effort of 7 editors and more than 200 scholars and scientists whose pioneering work has defined our understanding of stem cells, this book combines the prerequisites for a general understanding of adult and embryonic stem cells with a presentation by the world's experts of the latest research information about specific organ systems. From basic biology/mechanisms, early development, ectoderm, mesoderm, endoderm, and methods to the application of stem cells to specific human diseases, regulation and ethics, and patient perspectives, no topic in the field of stem cells is left uncovered.


Chapter 11.1 - Gregor Mendel

TIP: In any cross that is dihybrid (AaBb x AaBb) you will always get a 9:3:3:1 ratio, if you memorize this, you can save the trouble of doing a giant square!

A Mathematical Alternative (LAWS OF PROBABILITY)

A punnet square is not needed to determine the ratios of genotypes and phenotypes. Simple statistics and math can save you the trouble of filling out a square.

In a monohybrid cross Pp x Pp, each parent produced P gametes and p gametes

If you wanted to determine how many of the offspring are pp: x =

H is dominate for long hair (h = short) and B is dominate for black eyes (b = red eyes). If the parents are.

HhBb x hhBb

How many off the offspring will be short haired and red eyed?

Task: Use mathematical analysis to determine the number of short haired, black eyed offspring from the cross above.

TWO-TRAIT TEST CROSS

Used to determine the genotype of an "unknown" by crossing it with an individual that is homozygous recessive for both traits.

In flies (Long wings is dominant to short wings, Gray body is dominant to black)

A L __ G ___ is test crossed.

The offspring are 1:1:1:1 --> What is the genotype of the unknown parent?
If the offspring are half long winged & gray, and half long winged and black --> What is the genotype of the unknown parent?


Stem Cell & Regenerative Medicine Center

The U.S. Food and Drug Administration on Tuesday approved StrataGraft, a topical treatment for severe burns made from skin tissue, providing a boost for Madison-based firm Stratatech. Stratatech was founded in 2000 by SCRMC member Lynn Allen-Hoffman, the first female University of Wisconsin-Madison faculty member to start a biotech company.

June 16, 2021
The Cap Times

UW Begins New Clinical Trial to Treat Fatal Blood Disease in Children, Young Adults

The Food and Drug Administration-approved trial will use a form of transplant that replaces a patient’s bone marrow with alpha-beta T-cell depleted peripheral blood stem cells from closely matched unrelated donors or family members.

Stem Cell Research: Celebrating 25 Years Of Amazing Discoveries

Over the past two decades, stem cell research at UW-Madison has grown from involving a handful of scientists to nearly 100 from more than 30 schools, colleges and departments.

SCRMC member Daniel Z. Radecki recognized for his commitment to improving the lives of all postdocs

Nine University of Wisconsin–Madison postdoctoral researchers have been recognized with the inaugural Postdoc Excellence Awards for their teaching, service and mentoring. Daniel Z. Radecki (Comparative Biosciences) received one of these awards.

“The defining feature of Dan’s work with the (UW–Madison Postdoctoral Association) and others is his commitment to bettering the lives of all postdocs. He envisions how each event and initiative can best impact the individual, through the lenses of diversity and inclusion, immigration status, postdocs’ personal lives (e.g. childcare considerations), department/discipline, and more.”

Micro-molded ‘ice cube tray’ scaffold is next step in returning sight to injured retinas

Researchers at UW–Madison have made new photoreceptors from human pluripotent stem cells. However, it remains challenging to precisely deliver those photoreceptors within the diseased or damaged eye so that they can form appropriate connections, says David Gamm, director of the McPherson Eye Research Institute and professor of ophthalmology and visual sciences at the UW School of Medicine and Public Health.

“While it was a breakthrough to be able to make the spare parts — these photoreceptors — it’s still necessary to get them to the right spot so they can effectively reconstruct the retina,” he says. “So, we started thinking, ‘How can we deliver these cells in a more intelligent way?’ That’s when we reached out to our world-class engineers at UW–Madison.”

Metabolic switch may regenerate heart muscle following heart attack

Research from the University of Wisconsin–Madison finds that a new therapeutic approach for heart failure could help restore cardiac function by regenerating heart muscle. In a study recently published in the journal Circulation, the UW team describes its success in improving, in a mouse model, the function of heart muscle by temporarily blocking a key metabolic enzyme after a heart attack. This simple intervention, the researchers say, could ultimately help people regain cardiac function. “Our goal was to gain new understanding of how the heart can heal itself following injury at the molecular and cellular level and see if there was a way to restore cardiac function to an earlier state,” says UW–Madison’s Ahmed Mahmoud, professor of cell and regenerative biology in the School of Medicine and Public Health.

Learn more about the research here.
April 15, 2021

Individualized brain cell grafts reverse Parkinson’s symptoms in monkeys

Grafting neurons grown from monkeys’ own cells into their brains relieved the debilitating movement and depression symptoms associated with Parkinson’s disease, researchers at the University of Wisconsin–Madison reported today. In a study published in the journal Nature Medicine the UW team describes its success with neurons made from cells from the monkeys’ own bodies after reprogramming to induced pluripotent stem cells. UW–Madison neuroscientist Su-Chun Zhang, whose Waisman Center lab grew the brain cells, said this approach avoided complications with the primates’ immune systems and takes an important step toward a treatment for millions of human Parkinson’s patients. Learn more about their work here.
March 1, 2021

UW vision researchers partner with U.S. Department of Defense to develop stem cell therapy for combat-related eye injuries

The project, led by David Gamm, MD, PhD, director of the McPherson Eye Research Institute and professor of ophthalmology and visual sciences at the UW School of Medicine and Public Health, will develop a transplantable patch to restore vision to members of the armed forces who have been injured by blasts or lasers.
December 11, 2020

New Visualization Method Gets to the Heart of Parkinson’s Disease

This week, the NIH Office of Research Infrastructure Programs highlights Dr. Marina Emborg, her WNPRC lab team and their UW–Madison colleagues’ advances in detecting heart disease in Parkinson’s and evaluating new therapies that specifically target nerve disease within the human heart.
December 2020

Celebrating 25 Years of Embryonic Stem Cell Research at UW–Madison

It’s been 25 years since University of Wisconsin–Madison scientist James Thomson became the first in the world to successfully isolate and culture primate embryonic stem cells. He accomplished this breakthrough first with nonhuman primates at the Wisconsin National Primate Research Center in 1995, using rhesus monkey cells, then in 1996 with marmoset cells. Thomson then published his world-changing breakthrough on human embryonic stem cell derivation in Science on Nov. 6, 1998.
November 6, 2020

Study points way to possible new treatment for ligament injuries

“EEMs and exosomes each have attractive characteristics as therapeutics,” Dr. Hematti, UW-Madison’s Department of Medicine, noted.” As a cell therapy, EEMs will not proliferate or differentiate to undesirable cell types, which remains a concern for many stem cell therapies. Moreover, EEMs could be generated from a patient’s own monocytes using off-the-shelf exosomes, resulting in a faster and more facile process compared to autologous MSCs. Alternatively, exosome therapy could be a cell free, shelf-stable therapeutic to deliver biologically active components.” “Altogether, we believe our studies’ results support the use of EEMs and/or exosomes to improve ligament healing by modulating inflammation and tissue remodeling,” Dr. Vanderby concluded.
November 3, 2020


Solving the Morphology of Flowering Plants Multiple Choice Questions of Class 11 Biology Chapter 5 MCQ can be of extreme help as you will be aware of all the concepts. These MCQ Questions on Morphology of Flowering Plants Class 11 with answers pave for a quick revision of the Chapter thereby helping you to enhance subject knowledge. Have a glance at the MCQ of Chapter 5 Biology Class 11 and cross-check your answers during preparation.

I. Select the correct answer from the following questions:

Question 1.
Which one of the following is not a characteristic of root?
(a) Absence of buds
(b) Presence of chlorophyll
(c) Presence of root cap
(d) Presence of Unicellular hair

Answer: (b) Presence of chlorophyll

Question 2.
Roots that grow from any part of the plant body other than the radicle are called
(a) Tap roots
(b) Adventitious roots
(c) Modified roots
(d) Aerial roots

Answer: (b) Adventitious roots.

Question 3.
The place on stem or branch form where one or more leaves arise is called
(a) Apex
(b) Bud
(c) Internode
(d) Node

Question 4.
Which one of the following underground, fleshy structure is a stem?
(a) Carrot
(b) Potato
(c) Turnip
(d) Sweet Potato

Question 5.
Phyllode is a modification of
(a) Root
(b) Flower
(c) Petiole
(d) Bud

Question 6.
Potato tubers are formed at the tips of
(a) Primary roots
(b) Adventitious roots
(c) Petiole
(d) Stolons

Question 7.
Mesocarp and endocarp is the edible part of the fruit of
(a) Apple
(b) Mango
(c) Banana
(d) Litchi

Question 8.
Drupe is recognised by
(a) Stomy mesocarp
(b) Fleshy seed coat
(c) Thin seed coat
(d) Stony endocarp

Question 9.
What do you eat in coconut?
(a) Mesocarp
(b) Fruit wall
(c) Entire seed
(d) Embryo

Question 10.
The positions of shoot apex in monocot embryo is
(a) Lateral
(b) Basal
(c) Sub-terminal
(d) Terminal

Question 11.
In which one of the following plants the oil is stored in endosperm
(a) Coconut
(b) Ground nut
(c) Seasame
(d) Soyabean

Question 12.
In maize, the flower are
(a) Bisexual
(b) Unisexual but on the same plant
(c) Absent
(d) Unisexual but on different plants

Answer: (b) Unisexual but on the same plant

Question 13.
Epipetalous is condition of
(a) Aestivation of petal
(b) Placentation
(c) Stamens
(d) Position of ovary

Question 14.
A characteristic of angiosperm is
(a) Flower
(b) Root
(c) Seed
(d) All of these

Question 15.
An aspect of flower shown in floral formula but not in floral diagram is
(a) Aestivation
(b) Floral symmestry
(c) Position of ovary
(d) Cohesion of floral parts

Answer: (c) Position of ovary

Question 16.
In grass and banyan tree these are roots arising from parts of the plant other than the radicle, these are called
(a) Adventitious roots
(b) Fibrous root system
(c) Tap root system
(d) Tertiary root system

Answer: (a) Adventitious roots

Question 17.
In some leguminous plants the leaf base may become swollen, which is called the
(a) Pulvinus
(b) Lamina
(c) Petiole
(d) Leaf base

Question 18.
The arrangement of flowers on the floral axis is termed as
(a) Inflorescence
(b) racemose
(c) cymose
(d) thalamus

Question 19.
When the floral appendages are in multiple of 3,4 or 5 respec¬tively, a flower may be
(a) Trimerous
(b) Teramerous
(c) Pentamerous
(d) All of these types

Answer: (d) All of these types

Question 20.
A sterile stamen is called
(a) Staminode
(b) Stigma
(c) Apocarpous
(d) Syncarpous

Question 1.
Solanaceae is a large family, commonly called as the ‘…………’

Answer: Papilonoideae, Leguminosae

Question 3.
The following floral formula represents the …………… (Family: Brassicaceae)

Answer: calyx, perianth, androecium

Question 5.
The outer covering of endosperm separates the embryo by a layer called …………..

Question 6.
The embryo consists of one large and shield shaped cotyledon known as …………. and a short axis with a …………… and a radicle

Question 7.
Above the hilum, is a small pore called the …………..

Question 8.
If a fruit is formed without fertilisation of the ovary, it ……………

Answer: Parthenocarpic fruit.

Question 9.
The calyx is the outer most whorl of the flower and members are called ……………

Question 10.
If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called ……………

Question 11.
Flowers with bracts, reduced, leaf found in flower are called …………. and those without bracts, ……………

Answer: bracteate, ebracteate.

Answer: actinomorphic (regular), zymomorphic (bilateral)

Question 13.
A flower having only stamens or carpel is ………….

Question 14.
………….. is the pattern of arrangement of leaves on the stem or branch.

Question 15.
When the incisions of the lamina reach up to the midrib breaking it into a number of leaflets, the leaf is called ………….

III. Mark the statements True (T) or False (F):

Question 1.
The study of external features of plants is known as external morpholgy and that of internal features as anatomy.

Question 2.
The knowledge of external morpholgy of flowering plants is not essential for the study of all branches of botany.

Question 3.
The root is covered at the apex by a thimble-like structure called the not cap

Question 4.
A few millimetre above the root cap is the region of meristematic activity.

Question 5.
Tap roots of carrot, turnip and adventitious roots of sweet potato, get swollen and store food.

Question 6.
The main function of the stem is spreading out branches bearing leaves, flowers and fruits. It conducts water, minerals and photosynthates.

Question 7.
Underground stems of potato, ginger, turmeric, zaminkand modify to store food in them.

Question 8.
A typical leaf consists of three main parts: Leaf base, petiole and lamina.

Question 9.
In some leguminous plants the leafbase may become swollen, which is called the pulvinus.

Question 10.
The lamina or the leaf blade is the green expanded part of the leaf with veins and veinlets.

Question 11.
Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals and food materials.

Question 12.
Leaves are often modified to perform functions other than photosynthesis. They are converted into tendrils for climbing as in peas, or into spines for defence as in cacti.

Question 13.
Calyx and corolla are accessory organs, while androecium and gynoecium are reproductive organs.

Question 14.
When a flower has both androecium and gynoecium, it is termed as bisexual.

Question 15.
A flower is asymmetric or irregular, if it cannot be divided into similar halves by any vertical plane passing through the centre as in canna.

IV. Match the items of Column I

Answer:
(a) → 4
(b) → 15
(c) →13
(d) → 14
(e) → 1
(f) → 3
(g) → 2
(h) → 5
(i) → 6
(j) → 7
(k) → 8
(l) → 9
(m) → 10
(n) → 11
(o) → 12

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Watch the video: Stems. Biology (June 2022).


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