Anatomy of Flowering Plants Test - 13

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.

In temperate woody plants, the activity of vascular cambium is seasonal. The cambium is less active in autumn. This difference in secondary xylem growth due to the cyclic seasonal changes result in the formation of alternate rings of autumn wood and spring wood. These two zones constitute an annual or growth ring.

The axillary buds develop exogenously from the superficial meristematic cells derived from the apical meristem of the shoot.

The increase in lateral thickening is called as secondary thickening or secondary growth. This growth occurs in stem and root in dicotyledons. This development takes place in stele (interstellar secondary growth) and also in the cortex (extra stellar secondary growth). Both interfascicular and intrafascicular cambiums join to form a complete ring of cambium called as vascular cambium, which initiates interstellar secondary growth.

Tunica corpus theory was proposed by Schmidt in 1924. According to this theory, the shoot apex of the angiosperms has two distinct zones. The peripheral zone called as tunica and the central zone called as corpus. Tunica divides only in anticlinal plane and corpus divides in various planes.
Thus, the correct answer is option D.

Sclereids are reduced forms of sclerenchyma cells with highly thickened, lignified walls. These are star shaped. Sclereids are found in fruit or seed walls and also in the flesh of pear and pineapple. They are short and irregularly shaped. Their cell wall is very thick with many pit lines that are unevenly distributed.
So, the correct answer is option A- 'Sclereid'.

Primary growth initiated by apical meristems near tips of roots and shoots produce primary tissues that are partially differentiated into ground meristem that produce ground tissue protoderm that produce epidermis and procambium that produce primary vascular tissue. This theory was given by Haberlandt.
So, the correct answer is 'Habertlandt'

• 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'