Cold water treatment promotes ethylene production and dwarfing in tomato seedlings

Tomato (Lycopersicon esculentum Mill.) seedlings that were treated with cold water (5 °C) once a day, starting 14 d after sowing, were only 80% as tall as the control (25 °C water) plants after 21 d. The dwarfing effect was most conspicuous on the first internode length. Hypocotyl diameter and shoot fresh and dry weights were not significantly affected. A single cold water treatment induced ethylene production that peaked 60–90 min after treatment and then declined. Shoot segments excised above the first node had the highest rate of ethylene production. A single cold water treatment on day 21 resulted in an ethylene production rate of 19.6 nl h–1 g–1, compared to 3.4 nl h–1 g–1 for control seedlings (an increase of 5.8 times). Daily cold water treatment of 14-d-old seedlings for 2 weeks was equivalent to pretreatment with 3 mg l–1 of ethephon. Pretreatment of seedlings with 1 nl l–1 1-methylcyclopropane (1-MCP) was sufficient to block the ethylene action induced by the cold water treatment. It is inferred that cold water-induced dwarfism of tomato seedlings is mediated through ethylene action.