Why does the purple flower "Maciejka (Matthiola longipetala)" release its scent in the evening only?

Matthiola longipetala (night-scented stock)





There is nothing like relaxing in the garden on a warm summer's evening with floral scents perfuming the air. Many plants have nocturnal pollinators and so release their fragrance only at night. These include such familiar flora as honeysuckles (Lonicera species) and garden mignonette (Reseda odorata). A less familiar evening-scented herbaceous plant is night-scented stock (Matthiola longipetala), native from Greece to Southwest Asia, and a cousin of the better-known florist's stock (Matthiola incana). This cold-hardy annual grows about 1 1/2-feet tall and produces narrow, linear, three-inch-long gray-green leaves. The 3 1/4-inch wide, cross-shaped, highly fragrant pink, white, or lavender flowers are borne on racemes throughout the summer. Night-scented stock likes its summer cool, so it excels in northern zones. Give it full sun and regular moisture.





http://www.bbg.org/gar2/topics/plants/20...





http://en.wikipedia.org/wiki/Matthiola_l...





Good luck :-)

Why does the purple flower "Maciejka (Matthiola longipetala)" release its scent in the evening only?
Many flowers that release scent at night are pollinated by moths, insects that are active at night.