Exercise 11.6
Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?
Not cross-checked
NCERT prints no numerical answer for this exercise, so this working has not been cross-checked against the book.
Because a white or light-coloured flower remains visible in the dark, so the pollinators that are active at night can still find it.
A flower's colour is its advertisement to pollinators: the chapter notes that insect-pollinated flowers are often brightly coloured, produce nectar and give off fragrance to attract them.
In daylight, strong colours like red, yellow and orange stand out against green leaves, so day-blooming flowers use them.
After dark there is very little light and colours cannot be told apart; pale and white petals reflect the little light there is and show up against dark foliage, while a red or deep-coloured flower would simply disappear.
Night-blooming flowers usually back this up with a strong fragrance, which works in complete darkness where sight fails.
Being found means more visits, more pollen carried from anther to stigma, and so more fruits and seeds — reproductive success.