(1) indoleacetic acid, that is, auxin, can make cells elongate longitudinally and cause plant growth. It is a trace of organic matter, and the sensitivity of various plant organs and ducts to auxin is different. For example, roots are more sensitive than buds and stems, and auxin can be transported from the place of production to the place of action.

(2) Flowering is an important symbol of the transition from vegetative growth to reproductive growth of perennial plants, which is regulated by sunshine length, low temperature induction, plant age and other factors. According to the meaning of the question, gibberellin can promote the degradation of DEL protein in some plants, and DEL prevents SPL protein from playing its role. SPL directly activates the transcription of SOC coding genes, and the existence of SOC protein is a prerequisite for plant flowering, so DEL protein can inhibit flowering, while gibberellin, SPL protein and SOC protein can all.

(3) According to the meaning of the question, gibberellin will increase SOC, which is beneficial to flowering. Gibberellin degradation of DEL will increase the role of SPL, but when DEL increases, flowering is difficult to form. Only when the content of miR 156 is lower than the flowering value will there be flowering potential, according to the figure, there are four times.

(4) Because flowering will be accelerated when the expression of miR 156 is reduced, the vegetative growth period can be shortened by reducing the expression of miR 156.

So the answer is: (1)AD.

(2)C

(3) (4) Because Cardamine flexuosa has the potential to blossom only when the content of miRl56 in the plant is lower than the critical value of flowering, it can be judged that Cardamine flexuosa begins to blossom at the turn of the fourth winter and spring; Because the inhibitory effect on flowering can only be lifted when the FLC content reaches the lowest value, the flowering frequency of Cardamine flexuosa is one year 1 time.

(4) Decrease the expression of miR 156.