How are sclerenchyma and collenchyma different with respect to structure and function?

Sclerenchyma:

Sclerenchyma is a type of plant tissue composed of cells with thickened, lignified walls. These cells are dead at maturity and provide structural support to the plant.
  • Characteristics:
    • Cells have thick, rigid, lignified secondary cell walls.
    • Cells are usually dead at maturity.
    • Provide mechanical strength and support.
    • Two main types: fibers (elongated cells) and sclereids (short, irregularly shaped cells).

Collenchyma:

Collenchyma is a type of plant tissue consisting of living cells with unevenly thickened primary cell walls. These cells provide support while allowing flexibility and growth.
  • Characteristics:
    • Cells have unevenly thickened, non-lignified cell walls.
    • Cells are alive and can elongate.
    • Provide mechanical support, particularly in young growing parts of plants.
    • Often found in the cortex of stems, leaves, and petioles.

Sclerenchyma provides rigid, structural support, while collenchyma offers flexible support, particularly in growing regions. Both are specialized plant tissues that provide support, but they differ significantly in their structure and function.

Structural Differences

Sclerenchyma

Sclerenchyma cells are characterized by their very thick secondary cell walls, which are heavily lignified with lignin, a complex organic polymer that adds rigidity and resistance to decay. These cells are typically dead at maturity, having lost their cytoplasm and protoplasm, making them hard and inflexible.

Sclerenchyma tissue can be divided into two main types: fibers and sclereids. 
  1. Fibers: Fibers are long, slender cells usually grouped in bundles, providing substantial tensile strength and aiding in the resistance to stretching forces. 
  2. Sclereids: Sclereids, on the other hand, are shorter and variably shaped cells that contribute to the hardness and structural integrity of various plant parts, such as the gritty texture of pears and the tough shells of nuts.

Sclerenchyma cells are densely packed with minimal or no intercellular spaces, forming a compact tissue that enhances the plant's mechanical support and protection.

Collenchyma

Collenchyma cells have unevenly thickened primary cell walls, particularly thickened at the corners where cells meet. These walls are rich in pectin and cellulose, contributing to their flexibility and plasticity.

Collenchyma cells remain alive at maturity, retaining their cytoplasm and other cellular contents, which allows them to continue metabolic activities and support growth.

Unlike sclerenchyma, collenchyma cells do not have distinct subtypes but can vary in the pattern and degree of wall thickening, which can be continuous, lamellar, or angular.

Collenchyma tissues often have intercellular spaces, facilitating gas exchange and maintaining tissue flexibility. This tissue is typically found in young stems, leaves, and petioles, where it provides support while allowing for growth and elongation without compromising the plant's structural integrity.

Functional Differences

Sclerenchyma and collenchyma tissues in plants serve different functions, reflecting their distinct structural characteristics and roles within the plant body.

Sclerenchyma

Sclerenchyma's primary function is to provide rigid and durable support to the plant. The thick, lignified secondary cell walls of sclerenchyma cells make them extremely strong and resistant to mechanical stress. This rigidity is essential for maintaining the structural integrity of the plant, particularly in regions that are no longer growing.

Sclerenchyma cells are dead at maturity, which means they do not engage in metabolic activities. Instead, their empty, lignified walls form a tough framework that supports the plant against physical forces such as wind, pressure, and bending. This tissue is crucial in parts of the plant that need to be rigid and strong, such as the stems, roots, vascular bundles, and the hard shells of seeds and nuts.

In essence, sclerenchyma acts as the skeleton of the plant, ensuring that it remains upright and structurally sound under various environmental conditions.

Collenchyma

In contrast, collenchyma provides flexible and plastic support, especially to growing parts of the plant. The primary cell walls of collenchyma cells are unevenly thickened, particularly at the corners, and are rich in pectin and cellulose, allowing them to stretch and bend. This characteristic is crucial for supporting young, growing organs such as stems, leaves, and petioles without restricting their growth.

Collenchyma cells are living at maturity, which means they retain their protoplasm and continue metabolic activities that are essential for growth and development.

The flexibility of collenchyma cells enables them to provide support that can accommodate the elongation and expansion of plant tissues. They allow the plant to withstand mechanical stress from wind and physical impacts while still being able to grow and adapt to its environment. 



Read More:

SAQ 1

  1. What is a cell? What are the essential characteristics of cells?
  2. Explain the fluid mosaic model of the plasma membrane
  3. Which organelles are involved in photosynthesis?
  4. Why the mitochondria is called the powerhouse of the cell?
  5. Which organelle contains enzymes for cellular respiration?
  6. Why mitochondria and chloroplast are called semi-autonomous?
  7. Mention any two advantages of the extensive network of the endoplasmic reticulum
  8. What is the function of peroxisomes in plant cells?
  9. Explain the following terms: (a) chromatin network (b) chromosomes (c) Nucleosome (d) Solenoid Model
  10. What is the function of the nucleolus in the cell?

SAQ 2


Comments

Post a Comment

Popular posts from this blog

UNIT 1 – Mendel's Laws (Q&A) | MZO-002 MSCZOO | IGNOU

Image
SAQ 1 Fill in the blanks a) The title of the paper presented by Mendel in 1866 is ......................... . Answer: Experiments in Plant Hybridization b) The term 'genetics' was coined by ........................ . Answer: William Bateson c) Mendel proposed the concept of ...................... units. Answer: hereditary   d) Mendel's work was rediscovered by ........................., ........................... and .......................... . Answer: Carl Correns, Hugo de Vries and Erich von Tschermak SAQ 2 Answer in one word. a) In Mendelian crosses, progeny is produced from the mating of individuals in the parental generation. Answer: first filial generation or F1 b) The factors that regulate the inheritance of traits and act like discrete particles that remain separate. Answer: hereditary factors (genes) c) A genetic cross involving a single (mono) trait. Answer: monohybrid cross d) A trait/factor that remains hidden and not fully expressed in the progeny. Answer: re...
Read more

UNIT 16 – Cell Death and Renewal (Q&A) | MZO-001 MSCZOO | IGNOU

Image
SAQ i) Match the items in column I with column II: Answer: a) → iv;    b) → iii;    c) → vii;    d) → viii;    e) → vi;    f) → i;    g) → ii;    h) → x;    i) → v;    j) → xi;    k) → ix ii) Fill in the blanks: a) Autophagy includes the formation of three different vesicles including ....................., which circularizes to form ......................, which then fuses with a lysosome to form the ..................... . Answer: phagophore, autophagosome, autolysosome b) Apoptosis can be mediated by two modes or pathways, ....................... or ....................... . Answer: intrinsic, extrinsic c) Pharmacological inhibitors such as ....................... block the lysosomal proton transport and thus autophagy. Answer: Bafilomycin A1 d) ...................... is released from the mitochondria upon MOMP and binds to the adapter protein Apaf1 to form the complex known as ..........
Read more

UNIT 2 – Gene Action and Interactions (Q&A) | MZO-002 MSCZOO | IGNOU

Image
SAQ 1 Fill in the blanks with appropriate word: a) A condition in which a gene or gene pair suppresses or hinders the expression of another non-allelic gene is called ...................... . Answer: epistasis b) The phenotype effect gets enhanced because of the effect of ....................... genes. Answer: cumulative or additive  c) Red eye colour in Drosophila melanogaster is due to the deposition of pigment ...................... . Answer: drosopterins d) Progeny shows a ratio of ........................ in case of duplicate dominant epistasis.  Answer: 15 : 1 e) Epistasis in which a dominant allele at one locus can mask the expression of both (dominant and recessive) alleles at the second locus occurs due to .......................... gene interaction. Answer: inhibitory SAQ 2 State whether these statements are 'True' or 'False.' a) Pleiotropy occurs when a gene shows a complementary gene interaction with another gene. Answer: False b) Pleiotropic effects of albi...
Read more

What are the events involved in the S-phase of Interphase?

Image
The S-phase (Synthesis phase) is a critical part of interphase in the cell cycle, occurring between the G1 (gap 1) phase and the G2 (gap 2) phase. During this phase, the cell duplicates its DNA to prepare for cell division, ensuring that the genetic material is accurately passed on to the daughter cells. This phase is essential for maintaining genomic integrity and stability. Key Events in the S-phase 1. DNA Replication: The main event of the S-phase is DNA replication. This process ensures that the entire genome is copied so that each daughter cell will have an identical set of chromosomes. The helicase enzyme unwinds the DNA double helix, creating two single strands. These single strands act as templates for the synthesis of new complementary strands. 2. Activation of DNA Polymerases: DNA polymerases are key enzymes that catalyze the addition of new nucleotides to the growing strand. On the  leading strand,  DNA polymerase synthesizes continuously in the 5' to 3' direction. ...
Read more

Give a brief note on the control of the Cell Cycle

The cell cycle is a highly regulated process that ensures cells grow, replicate their DNA and divide accurately. Its control is crucial for normal development, tissue repair and prevention of diseases like cancer. This control is achieved mainly through a combination of regulatory proteins, checkpoints, inhibitory pathways and external signaling factors, all of which coordinate to monitor and regulate the progression of the cycle at every stage. 1. Cyclins and CDKs – The Core Regulators Cyclin-dependent kinases (CDKs) are special enzymes that become  active only when  they bind to a protein called  cyclin,  to form a  cyclin-CDK complex.  Different cyclins appear and disappear at specific times in the cell cycle, and this timing controls CDK activity. Each cyclin-CDK complex triggers important events of a particular phase of cell cycle. In the G1 phase,  Cyclin D binds to CDK4 or CDK6 to push the cell toward the S phase. During the S phase,  Cycli...
Read more

UNIT 3 – Gene Structure and Function (Q&A) | MZO-002 MSCZOO | IGNOU

Image
SAQ 1 i) Define Recon, Muton and Cistron. The terms Recon, Muton and Cistron were introduced by Seymour Benzer during the 1950s to study the detailed structure and function of genes at the molecular level. He worked on the rII region of T4 bacteriophage and used bacteriophage genetics to analyze how small changes in DNA affect phenotypes. At that time, the gene was considered as a single indivisible unit. But Benzer showed that a gene has a finer internal structure and can be divided into smaller functional units. Based on this, he proposed three molecular units: Recon, Muton and Cistron, each having a specific role related to recombination, mutation and expression. Recon Recon is defined as the smallest unit of recombination. It refers to the smallest segment of DNA within which crossing over cannot occur, but recombination can occur between two such units. According to modern molecular understanding, recombination between two genes or within a gene occurs at the level of nucleotid...
Read more

What is intracellular protein turnover?

Intracellular protein turnover is the continuous and regulated process by which proteins inside a cell are  synthesized  (built or formed) and  degraded  (broken down). This process plays a vital role in maintaining the cell's internal balance, known as  proteostasis.  It ensures that old, misfolded, damaged, and excess proteins are efficiently removed and replaced with newly synthesized, functional proteins. This dynamic balance between synthesis and degradation helps the cell adapt to changes, control growth, respond to stress and perform normal physiological functions. Each protein inside the cell has a specific half-life or lifespan. Some proteins are very short-lived and degrade within minutes, while others may last for hours or days. When a protein becomes non-functional, either due to damage or mutation, it must be removed. If this removal does not happen properly, faulty or misfolded proteins may accumulate and cause various diseases, including canc...
Read more

UNIT 4 – Linkage, Crossing Over and Mapping in Eukaryotes (Q&A) | MZO-002 MSCZOO | IGNOU

Image
SAQ 1 a) What is gene mapping? How do the linked genes help in gene mapping? Gene mapping is the method used to determine the location of genes on a chromosome and the distance between them. It helps in identifying the exact position of a gene responsible for a particular trait or disease. The concept started with the work of Thomas Hunt Morgan in the early 1900s when he studied Drosophila melanogaster (fruit fly) and observed that some traits are inherited together. This was because the genes responsible for those traits were located close to each other on the same chromosome. This phenomenon is known as linkage. There are two main types of gene mapping: 1. Genetic Mapping (Linkage Mapping): Genetic mapping uses the frequency of recombination or crossing over between genes to estimate their distance on a chromosome. It gives a relative position of genes rather than their exact physical location. 2. Physical Mapping Physical mapping uses molecular biology techniques to determine the e...
Read more

What is Cyclin-CDKs kinases? Write a brief note on the relation of cyclin with CDKs

Image
Cyclin-CDK kinases are enzyme complexes that control the progression of the eukaryotic cell cycle. These complexes consist of two main components: a  cyclin protein  and a  cyclin-dependent kinase (CDK).  CDKs are serine/threonine protein kinases that are present in the cell in an  inactive form.  They require the binding of a regulatory protein, called a  cyclin,  to become  active.  Once a cyclin binds to a CDK, the complex becomes enzymatically active and can phosphorylate various target proteins involved in controlling key steps of the cell cycle, such as DNA replication, chromosome condensation and mitotic spindle formation. The activity of cyclin-CDK complexes is regulated at multiple levels, including cyclin synthesis and degradation, phosphorylation and dephosphorylation of CDKs, and the presence of CDK inhibitors (CKIs). This regulation ensures that each phase of the cell cycle occurs only once and in the proper order, preventin...
Read more

UNIT 5 – Mutation and Repair (Q&A) | MZO-002 MSCZOO | IGNOU

SAQ 1 Fill in the blanks/choose the correct option for each statement given below: a) In ....................... mutation one purine (or pyrimidine) is replaced by the other. i) transversion ii) transition iii) frameshift iv) All of the above are false Answer: ii) transition b) Which of the following is true for Tandem duplication mutations? i) play an important role in evolution ii) arise during the same ectopic recombination as deletions iii) occur within a single gene usually inactivate the gene and are not leaky iv) All the above are correct Answer: iv) All the above are correct c) Which of the following is a change in the sequence that leads to formation of a stop codon? i) missense mutation ii) nonsense mutation iii) silent mutation iv) deletion mutation Answer: ii) nonsense mutation d) The formation of pyrimidine dimers results from which of the following? i) spontaneous errors by DNA polymerase ii) exposure to gamma radiation iii) exposure to ultraviolet radiation iv) exposure...
Read more