The flower is the reproductive organ of the plant. Without flowers, plants would not be able to reproduce sexually.
The colour and smell of the flower attract insect and animals to cross pollinate the plant
While a hummingbird is sipping nectar from a plant, it is also cross pollinating the plant as it passes from flower to flower.
sepals and petals
The petal aids the flower for pollination only, it provides no other function to the plant at all. See related question.
I've forgotten a lot of this, but I think a flower's fragrance, color, and pollen attract bees and birds which help shake the pollen down the stem to the reproductive parts of the flower. Basically, the flower woos the pollinators, which inadvertently keep the plant reproducing and alive.
pollination
Roots transport nutrients and water to the main flower/plant. They also help support the flower/plant and keep it anchored.
The flower attracts insects which helps the plant grow!
It has special food for the plant along with good chemicals that help the flower prosper.
help
Flower.
While a hummingbird is sipping nectar from a plant, it is also cross pollinating the plant as it passes from flower to flower.
A flower is a characteristic for the entire family of that plant. It incorporates some traits also, such as flower color, smell and floral biology etc. Characteristics of flower help in plant identification to a greater extent.
The pistil and stamen help the plant reproduce.
In most plants, this would be the flower; specifically, the petals.
sepals and petals
An angiosperm is a flowering plant. The flower is how the plant reproduces sexually. This allows for hybridzation and variation. Plants that reproduce by spores have less variation.
Plants don't have needs. The purpose of a plant is to reproduce and the flower helps a plant do that by attracting insects that will facilitate fertilization