Plant hormone regulation plays an important role in plant growth and development.

(1) As can be seen from the results in the table, the physiological effects caused by the same hormone at different growth and development stages of plants are different; Among these five hormones, auxin, cytokinin and gibberellin play a synergistic role in the regulation of fruit growth. The results in the table show that the normal growth and development process of plants is not the function of a certain plant hormone, but the result of the joint action of many hormones.

(2) Abscisic acid is easy to degrade at high temperature. When the wheat is about to mature, if it experiences a period of dry heat and meets with heavy rain, the seeds will easily germinate in the ear. It can be known that abscisic acid can promote seed dormancy and inhibit germination, and water is necessary for seed germination;

(3) According to the general steps of the experiment, the following results can be obtained: (2) The two groups of seedlings were treated differently, that is, distilled water and gibberellin solution were sprayed on the seedlings of group A and group B respectively with a watering can; ③ Observe the dependent variable of the experiment, that is, the height of the two groups of plants. Gibberellin can promote cell elongation and increase plant height, and plants treated with gibberellin can significantly increase plant height, so the predicted experimental results are that plants in group A are shorter than those in group B. 。

So the answer is:

(1) Different auxins, cytokinins and gibberellins work together.

(2) Promoting seed dormancy and inhibiting water required for seed germination.

(3) (2) The gibberellin solution (3) with appropriate concentration is the same, and the average height of plants in Group A (control group) is smaller than that in Group B (experimental group).