Abstract:

【Objective】 The purpose of this paper is to investigate the mechanism of drought induced cross adaptation to low temperature stress in cucumber (Cucumis sativa L) seedlings. 【Method】 ‘Jinyou 3’ cucumber seedlings were used as experimental materials. Seedlings were pretreated under drought condition, which simulated with 10% polyethylene glycol (PEG) for 2 d. Recovered 2 d later, the pretreated and non-pretreated seedlings (control) were displaced into growth chambers and treated under low temperature (day/night temperature is 8℃/5℃). 【Result】 The results showed that low temperature stress significantly decreased the relative water content, water potential and osmotic potential, while increased proline, soluble sugar and soluble protein contents. Pretreated with 10% PEG before exposure to stress condition, cucumber seedlings showed a significant low decreased degree in relative water content, water potential and osmotic potential, while high increased degree in proline, soluble sugar and soluble protein contents, in comparison with non-pretreated seedlings. At the end of the experiment (7 d), the relative water content of seedlings pretreated with PEG increased by 24.7 percentage points, the water potential and osmotic potential increased by 0.35 MPa and 0.13 MPa, respectively, and the proline, soluble sugar and soluble protein contents increased by 41.4 %, 80.8 % and 260.7 %, respectively, in comparison with non-pretreated seedlings. 【Conclusion】 Drought pretreatment could induce the cross adaptation to low temperature in cucumber seedlings, and the adaptation might be related to the observed increase in osmoregulation capability.

Key words: cucumber (Cucumis sativa L), low temperature, cross adaptation, polyethylene glycol (PEG-6000), osmoregulation