Important questions based on NCERT syllabus for Chapter 15 - Plant Growth and Development:
Question-1: In botanical gardens and tea gardens, gardeners trim the plants regularly so that they remain bushy. Does this practice have any scientific explanation?
Solution: Mostly in higher plants, the growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called apical dominance. Removal of shoot tips (decapitation) usually results in the growth of lateral buds. Hence, in botanical gardens and tea gardens, gardeners trim the plants regularly so that they remain bushy.
Question-2: Nicotiana tobacum, a short-day plant, when exposed to more than critical period of light fails to flower. Explain.
Solution: a. Some plants require a periodic exposure to alternate light and dark for its flowering response. This phenomenon is termed photoperiodism.
b. The requirement of light exposure is critical. The SDP plants, when exposed to light period in excess of critical period fail to flower,
c. Those plants which require exposure to light period at critical or more than critical period for its flowering response are called long-dayplant.
d. Nicotiana tabacum fails to flower if exposed to more than critical period of light because it is an SDP.
Question-3: Does the growth pattern in plants differ from that in animals? Do all the parts of plant grow indefinitely? If not, name the regions of plant, which can grow indefinitely.
Solution: Yes, the growth pattern in plants differ from that in animals. Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. This ability of the plants is due to the presence of meristems at certain locations in their body. The cells of such meristems have the capacity to divide and self-perpetuate. The product, however, soon loses the capacity to divide and such cells make up the plant body. This form of growth wherein new cells are always being added to the plant body by the activity of the meristem is called the open form of growth.