A variety of wheat tolerant to deep-seeding conditions: Elongation of the first internode depends on the response to gibberellin and potassium

The addition of gibberellin A₃ (GA₃) to culture media induced a dramatic elongation of the first internode in Hong Mang Mai, a wheat variety tolerant to deep-seeding conditions. The length of the first internode in the GA₃-treated seedlings reached approximately 45 cm, which is twice as long as that of the control, whereas first internodes of other varieties were 3 to 12 cm long and hardly affected by GA₃. The level of endogenous gibberellins (GA) in Hong Mang Mai was not greater than that of other wheat varieties. The expression of GAMyb, a transcription factor, was abundant in the first internode and substantially increased by GA₃ application in Hong Mang Mai, compared with other wheat varieties. These results suggest that the first internode of Hong Mang Mai is more sensitive to GA in inducing strong elongation. The presence of potassium in the culture media was indispensable for the first internode elongation. Application of GA₃ enhanced the uptake of potassium in Hong Mang Mai. Higher sensitivity of the first internode to GA could cause strong elongation by increasing the amount of osmotic solute, which plays an important role in the tolerance mechanism of Hong Mang Mai to deep-seeding conditions.