Question

Colour of night-blooming flowers is usually
(a)Violet to purple
(b)Red
(c)Yellow
(d)Whitish

Answer 1

Hint: Flowers are the main reproductive organs of a plant. They are used to attract pollinators like birds and insects. They do so by producing scents and attractive colours. However, at night the colours that are more visible are not bright colours but plain colours.

Complete answer:
Flowers are the main reproductive organs which house the male and female gametophytes. Fertilization of plants takes place through pollination which takes place through pollinators like insects and birds.
In order to attract pollinators, flowers provide nectar meals and are present in different colours and give out different scents. However, for the plants that are blooming at night, insects and birds generally don’t visualize the colours very well. In such plants, flowers generally produce a sweet smell to attract the pollinators. Plants do not waste much of their resources in producing coloured pigments, which will not be visible at night.
So, in plants with night-blooming flowers, the flowers tend to be whitish in colour which is much more visible in the dark and they also tend to produce a scent to attract the pollinators instead or are pollinated by wind(anemophilous).

Additional Information:
 Insects, small birds and mammals like bats or hummingbirds help in the pollination of plants. They are attracted by the scent or colour of the flowers to get nectar meal. While they obtain nectar, pollen grains stick to their bodies and are transferred to other flowers thus bringing about pollination.
However, this is not the only method of pollination. Some plants undergo pollination by wind or water too.
So, the correct answer is, ‘Whitish.’

Note: Not all the night-blooming flowers are whitish in colour.
There are exceptions where the flowers are pigmented and attract the pollinators by scent instead, like the evening primrose.
The evening primrose is yellow in colour and it attracts the insects by strong scent instead of colours.