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.

Deep-seeding and ethylene were found to stimulate extension growth of the first internode of intact wheat {Triticum aestivum L.) seedlings in darkness. Seedlings of Hon Mang Mai emerged from much deeper in the soil than the seedlings of the other varieties used and their first internodes elongated to a much greater extent in response to ethylene. Carbon dioxide slowed elongation of the first internode and inhibited ethylene action. Elongation of the first internode due to deep-seeding and ethylene treatment showed high heritahilities, suggesting a genetic basis underlying those traits.

Stage of maturity often affects the yield, dry matter, specific gravity and color of potato tubers.

No abstract

Either ethylene or carbon dioxide stimulated the growth of oat mesocotyls in darkness, although the effect was much greater for carbon dioxide. Maximum elongation was obtained in the presence of both gases. Ethylene also induced lateral expansion of the mesocotyl: the volume of the mesocotyl was increased more in air with added ethylene than in air depleted of ethylene. Ethylene also stimulated mesocotyl growth under red light. Gibberellin only slightly increased mesocotyl length under red light and acted cooperatively with ethylene in the promotion of growth. The oat mesocotyl is a unique organ in terrestrial plants because ethylene simultaneously stimulates not only longitudinal growth but also lateral expansion. The ecological significance of oat mesocotyl growth in relation to the response to ethylene and carbon dioxide is discussed.