"Heliotropic" means to move or grow in the direction of the sun (such as the plant called Heliotrope), which may or may not be what you were looking for.
Dawn.
D
A four letter word meaning to grow light as the sun rises is dawn.
Dawn is the four letter word meaning to grow light as the sun rises. Dawn is the beginning of a new day.
dawn
dawn
d for dawn
d for dawn
Dawn.
dawn
dawn
d for dawn