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 Chapter 6 

 Anatomy of Flowering Plants 



Q1. State the location and function of different types of meristems.
Answer: The location and function of different types of meristems are:
    • Apical meristems 
      Location: Present at the tips of roots and shoots.
      Function:  Produce primary tissues and also helps in elongation of stem and root.
    • Intercalary meristems
      Location: Present between mature tissues. 
      Function:  Helps in regeneration of grasses that are removed by the grazing herbivores.
    • Lateral meristems
      Location:  Occur in the mature regions of shoots and roots of many plants, particularly in those which produces woody axis. 
      Function: Responsible for producing the secondary tissues.


Q2. Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.
Answer:  Cork cambium is a meristematic tissue that grows in the mature stem cortex region. It is formed to substitute the broken epidermal layer of stem. At the outer side, the cells are cut off by cork cambium and form the cork. Hence, cork cambium can be said as a tissue that forms cork.


Q3. Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?
Answer: In most dicotyledonous plants, the girth increase which is said as secondary growth. The tissues that involved in this growth are the two lateral meristems: vascular cambium and cork cambium. In the young stem vascular meristem is present in patches as a single layer between the xylem and phloem which later form a complete ring. The cells of medullary rays, adjoining the intrafascicular cambium become meristematic and form the interfascicular cambium. Thus, a continuous cambium ring is formed. The cambial ring becomes active and begins to cut off new cells, both on the inner and the outer sides. The cells which cut off towards pith, mature into secondary xylem and the cells that cut off towards periphery are mature into secondary phloem. Generally, the cambium is more active on the inner side than on the outer side. As a result, a large number of secondary xylem is produced as compared to secondary phloem and soon forms a compact mass. 
The outer cortical and epidermis layers get broken and need to be replaced to provide new protective cell layers. Hence, another meristematic tissue called cork cambium or phellogen develops, usually in the cortex region. Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem while the inner cells differentiate into secondary cortex or phelloderm. Phellogen, phellem, and phelloderm are collectively known as Periderm. Secondary growth is essential for growth in girth of the stem.


 
Fig: Schematic diagram of secondary growth in dicot stem.


Q4. Draw illustrations to bring out the anatomical difference between
a. Monocot root and Dicot root
b. Monocot stem and Dicot stem

Answer: 
a. Monocot root                               Dicot root









b. Monocot stem                            Dicot stem
 









Q5. Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or dicot stem? Give reasons.
Answer: In here the question ask you to collect a transverse section of young stem of a plant and observe it under microscope and write whether it is monocot or dicot with reasons.
If the observe plant’s vascular bundles are arranged in a ring then it is said to be dicot stem and if the vascular bundles are scattered then it is said to be monocot stem.


Q6. The transverse section of a plant material shows the following anatomical features- a) the vascular bundles are conjoint, scattered and surrounded by a schlerenchymatous bundle sheaths. b) phloem parenchyma is absent. What will you identify as?
Answer: The transverse section of a plant material shows monocot stems.



Q7. Why xylem and phloem are called complex tissues?
Answer: Xylem and phloem are called complex tissues because they are made of more than one type of cells and these works together as a unit.



Q8. What is stomatal apparatus? Explain the structure of stomata with a labelled diagram.
Answer: The stomatal aperture, guard cells and the surrounding subsidiary cells are together called as stomatal apparatus.
Stomata are structures found in the epidermis of leaves. Each stoma is composed of two bean-shaped cells known as guard cells which enclose stomatal pore. The outer walls of guard cells are thin and the inner walls are highly thickened. The guard cells possess chloroplasts and regulate the opening and closing of stomata. A few epidermal cells, in the vicinity of the guard cells become specialised in their shape and size are known as subsidiary cells.

 

Q9. Name the three basic tissue systems in the flowering plants. Give the tissue names under each system.
Answer:  The three basic tissue systems in the flowering plants are: 
    •Epidermal tissue system
        Epidermis
        Stomata
        root hairs
        trichomes
    •Ground tissue system
        Parenchyma
        Collenchyma
        Schlerenchyma
    •Vascular tissue system
        Xylem
        Phloem


Q10. How is the study of plant anatomy useful to us?
Answer: The study of plant anatomy help us to understand the internal structure of the plant. It also helps us to understand the evolution that has occurred among the plants.


Q11. What is Periderm? How does Periderm formation take place in the dicot stems?
Answer: The outer cortical and epidermis layers get broken and need to be replaced to provide new protective cell layers. Hence, another meristematic tissue called cork cambium or phellogen develops, usually in the cortex region. Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem while the inner cells differentiate into secondary cortex or phelloderm. Phellogen, phellem, and phelloderm are collectively known as Periderm.


Q12. Describe the internal structure of a dorsiventral leaf with the help of labelled diagrams.
Answer: The internal structure of a dorsiventral leaf shows three main parts and they are epidermis, mesophyll, and vascular system.
    • The epidermis which covers both the upper surface i.e., adaxial epidermis and lower surface i.e., abaxial epidermis of the leaf. The adaxial epidermis contains more stomata than the adaxial epidermis.
    • The tissue between the upper and lower epidermis is mesophyll which possess chloroplasts and carry out photosynthesis. Mesophyll consists of two types of cells- palisade parenchyma and spongy parenchyma.
    • Vascular system contains vascular bundles which are present in the veins and the midrib. The vascular bundles are surrounded by a layer of thick walled called bundle sheath cells.

 
Fig: The internal structure of a dorsiventral leaf


Dipannita Das





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