Question

The change that occurs in apex at the time of flowering is
(a)Meristem gets destroyed
(b)Vegetative apex changes into reproduction apex
(c)Meristem decreases its activity
(d)All of the above

Answer 1

Hint: The transformation of the vegetative apex into a reproductive primordium is probably the greatest ontogenetic change taking place within the plant. The time sequence of events in particular to the species and transformation may occur within several hours or even a few minutes.

Complete answer:
At the time of flowering, the vegetative shoot apex gets changed into a reproductive shoot apex (reproductive phase). This transformation of shoot apex is done by florigen and light.
The summit zone of the reproductive shoot apex is active as the rate of cell division is observed to be greater and it forms stamens and carpels.
Whereas, the flank zone is less active in the reproductive shoot apex and it forms sepals and petals.

Additional Information:
-The basic structure of the plant body is formed due to the differentiation of meristematic tissues.
-The meristematic cells have a thin cell wall and no intercellular space.
-The cells are small filled with protoplasm and no vacuole present, and the plastids are rudimentary in the form of proplastids.
-Meristematic tissues are of three types:
  -Apical meristematic tissue (present at the tips)
  -Intercalary meristematic tissue (present in the middle)
  -Lateral meristematic tissue (present at the sides)
-A central zone is present in the center of meristematic tissue having stem cells and helps in the maintenance of meristem.
-The shoot apical meristem develops the above-ground organs while the root apical meristem develops the below-ground organs and tissues.
So, the correct answer is 'Vegetative apex changes into reproductive apex'.

Note: The transformation of the vegetative apex into a reproductive primordium is probably the greatest ontogenetic change taking place within the plant. The time sequence of events in particular to the species and transformation may occur within several hours or even a few minutes. After photoperiodic induction, the vegetative apex, hitherto capable of unlimited growth, is transformed into a determinate flower primordium or inflorescence. The transformation of the vegetative apex is accompanied by the morphogenesis of modified leaves, bracts, and bracteoles, the sequence indicating the switch over" from one developmental phase to the other occurs in stages.