Question

If parenchyma cells have the ability to divide , how are they permanent tissues ?

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Answer 1

Answer:

Meristematic tissue is the dividing tissue present in the growing regions of the plant. Permanent tissues are derived from meristematic tissue once they lose the ability to divide. They are classified as simple and complex tissues. Parenchyma, collenchyma and sclerenchyma are three types of simple tissues.

Answer 2

A tumour is due to dedifferentiation as cells have regained the ability to divide.

Parenchyma cells are simple permanent tissues which have lost the capacity to divide.

When they r made to divide again it only means that they are dedifferentiating.

The main characteristics of parenchyma are:

• They are living permanent tissues that have the ability to divide at maturity and help in the regeneration and healing of wounds

• Parenchyma cells are the foundation of a plant as reproductive cells (spores, gametes) are parenchymatous in nature

• Single parenchyma cell of a zygote has an ability to develop into an entire plant. These cells are called “totipotent” cells

• Parenchyma cells occur in the form of continuous masses as homogeneous parenchyma tissues e.g. in pith and cortex of stems and roots, mesophyll of leaves, the flesh of succulent fruits and in the endosperm of seeds

• Parenchyma cells may be associated with other types of cells to form heterogeneous complex tissues such as parenchyma of xylem and phloem

• Parenchyma cells are essential for activities like photosynthesis, storage, secretion, assimilation, respiration, excretion and radial transport of water and solute

• Structure of Parenchyma Cells

• It is a living cell

• It has a prominent nucleus and protoplast

• The cells of parenchyma are isodiametric or polyhedral in shape. They may be polygonal, oval, round or elongated

• These cells are closely packed or may have small intercellular space

• They are made up of thin cell wall made up of cellulose, hemicellulose
• Plasmodesmata join the cells of the parenchyma tissue

• They have several small vacuoles. In the older parenchyma, smaller vacuoles merge to become a large central vacuole, which may accumulate anthocyanin or tannins

• Water is abundant in the vacuoles of the parenchyma cells that act as a water reservoir

• Storage parenchyma cells may have thick xyloglucan walls e.g. in the endosperm of the date palm. The sugar is used during germination and walls become thin

• The parenchyma cells of flowers and fruits contain chromoplasts
• Parenchyma cells may have a thick lignified wall that makes it difficult to differentiate it from sclerenchyma

• Hydraulic property of cells gives the parenchyma its mechanical strength

• Chloroplasts are present in the parenchyma cells that are specified to perform photosynthesis

• The parenchyma cells which perform a secretory function, have dense protoplasm that is rich in ribosomes, Golgi bodies and a highly developed endoplasmic reticulum

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