Read the following passage: When all parts of a flower are ripe, the flower is unfolded and the stamens are exposed, which is flowering. Different plants bloom at different ages.

(1) comes from the essay "Winter wheat is sown and germinated in autumn, and blooms and bears fruit in early summer of the following year. For this kind of plants, the low temperature in late autumn and early winter becomes a necessary condition for flowering; Under the condition of long sunshine, American tobacco can't bloom when the plant height is 3-5 m in summer, but it can bloom when the plant height is less than 1m when it grows in greenhouse in winter. " It can be known that the external conditions that affect flowering are mainly temperature and sunshine time.

(2) Because "winter wheat is sown and germinated in autumn, and blooms and bears fruit in early summer of the following year, low temperature in late autumn and early winter becomes a necessary condition for this kind of plants to blossom", if winter wheat is replanted in spring, it will only grow seedlings without flowering and bearing fruit without low temperature treatment in late autumn and early winter.

(3) American tobacco plants are 3-5 meters high and consist of leaves, which are vegetative organs, while wheat ears belong to fruits and are reproductive organs.

So, the answer is: (1) temperature; Light;

(2) Low temperature in late autumn and early winter is a necessary condition for flowering; ?

(3) nutrition; breed