CBSE Questions for Class 11 Medical Biology Anatomy Of Flowering Plants Quiz 2 - MCQExams.com

Solution

Correct answer is option D.
Explanation for correct option:

• In extrastelar secondary growth, epidermis and pericycle with parenchyma or collenchyma cells acquire secondary meristematic property by de-differentiation and is called cork cambium. It is a lateral meristem that helps in secondary growth. It produces tough protective material called cork.
• The phelloderm is present inside the cork cambium.
• The phelloderm (secondary cortex), phellogen (cork cambium) and phellem (cork) are the primary covering layer when the epidermis gets ruptured. This periderm is a protective layer of the dicot stem.

Solution

Correct answer is option A.
Explanation for correct option:

• In extrastelar secondary growth, epidermis and pericycle, with parenchyma or collenchyma cells acquire secondary meristematic property by de-differentiation and is called phellogen or cork cambium.
• Cork cambium is a lateral meristem that helps in secondary growth. It produces tough protective material called cork.

• The cambium present within the vascular bundle is called intrafascicular cambium. It is present between the primary xylem and primary phloem. It is primary in origin. 
• Procambium is the primary meristem of a plant that forms the cambium and primary vascular tissues.
• Cork cambium is the tissue found in many vascular plants as part of the periderm. It is found in the stem and gives rise to cork on its outer surface and a layer of cells containing chlorophyll on its outer.
• The new strip of cambium which is formed from the permanent cells of interfascicular parenchyma is called the interfascicular cambium. It is secondary in origin as it is derived from the permanent cells of medullary rays. 

• The activity of cambium is under the control of many physiological and environmental factors.
  
•  In the spring season, cambium is very active and produces a large number of xylary elements having vessels with wider cavities. The wood formed during this season is called spring wood or early wood.
  
•  In winter, the cambium is less active and forms fewer xylary elements that have narrow vessels, and this wood is called autumn wood or late wood.
  
• The spring wood is lighter in colour and has a lower density whereas the autumn wood is darker and has a higher density.
  
• So, the correct answer is ' Early wood'

• Procambium lies inside of the protoderm and develops into the primary xylem and primary phloem. It also produces the vascular cambium. 
• A few parenchyma cells of the medullary rays adjacent to intrafascicular cambium dedifferentiate into meristematic cells and form the interfascicular cambium (in between vascular bundle).

• A meristem is made of dividing cells. 
• They are in parts of the plant where growth can take place.
• Shoot apical meristem tissue is found at the tip of the stem. 
• It undergoes cell division and is responsible for stem elongation.
  

• Xylem is the water-conducting tissue. It consists of living cells like parenchyma and dead cells like tracheary elements and fibers. 
• These cells except parenchyma take part mostly in the conduction of water and nutrients. 
• Parenchyma cells in the xylem help in storage, maintaining osmotic balance, etc, and are capable of division by undergoing differentiation.

• Tissues are groups of similar cells with the same functions and origin.
• Organelles are small bodies within a cell with specific functions.
• Organs are made of a group of tissues that function together.
• Organ systems are made up of a group of organs that functions together.

• Xylem is a complex permanent tissue that has lignified secondary cell walls. 
• Due to heavy lignin deposition, the cell wall of xylem cells is rich in lignin.
• It is mainly present in xylem fibres, tracheids and vessels.
  

Even, if there is more than one tunica layer in the stem apex, only the outer layer will develop into the epidermal cells. The stem has three simple cell types, i.e. the parenchyma, collenchyma and sclerenchyma cells which are responsible for the metabolic functions, repairing and healing wounds and storing starch.

The correct option is B.

Schmidt has postulated tunica- corpus theory on the basis of studies of shoot apices of angiosperm. This theory is concerned with planes of cell division in the apex. In contrast to apical cell theory, the tunica-corpus theory is applicable only to shoot apex and not to root. There are three types of meristematic tissues like apical (at the tips), intercalary (in the middle) and third as lateral (at the sides).

Schmidt distinguished two tissue zones in the shoot apex and termed as tunica and corpus.

The correct answer is B.

• The endodermis of the dicot stem is the central, innermost layer of the cortex.
• The endodermis is made up of barrel-shaped cells which do not enclose intercellular space.
• The endodermis helps to regulate the movement of water, ions, and hormones into and out of the vascular system. It may also store starch grains as a food reserve.
• Thus, the stem of the endodermis of the dicot stem is called starch sheath.
• So, the correct answer is option B.

• The anatomical study of a transverse section of the dicotyledonous root shows the presence of bundles and pericycle. 
• The xylem and phloem that make up the vascular bundles are enclosed by the endodermis. However, the number of vascular bundles is limited to 2-6 or a maximum 8.
• Vascular bundles of the dicot root are described as radial.
  
• Pith is absent in the older root. Secondary growth is present in dicots and absent in monocots.