Question

If a tree flowers thrice in a year (Oct., Jan. and July) in Northern India, it is said to be

(a) photo and thermo-insensitive

(b) photo and thermo-sensitive

(c) photosensitive but thermo-insensitive

(d) thermosensitive but photo-insensitive.

Answer 1

Ans (a ) photo and thermo - insensitive

Light and temperature are the extrinsic factors for the initiation of flowers.

Photoperiodism : a periodic exposure of light to induce flowering .some plants require the exposure to light for a period exceding critical duration and some plants must be exposed to light for a period less than critical duration before the flowering initiating in them .The former group of plants called long day plants and the latter groups called short day plants. And the some plants where there is no correlation between exposure to light duration and induction of flowering response are day neutral plants.

The duration of light period and the dark period having the equal importance in flowering . Means flowering depends upon the relative duration of light and dark ( photoperiodism ).

Vernalisation : It is the second factor for plants for which flowering is either quantitatively or qualitatively dependent on exposure to low temperature.