Abstract: 【Objective】 The mechanisms of Cerasus sachalinensis Kom. seedlings responding to water stress were studied in order to provide a academic and practical basis for evaluating the resource characteristics.【Method】 Changes of root respiratory pathways, related enzyme activities, respiratory substrates and chlorophyll fluorescence parameters of leaves were determined using continual drought and waterlogging treatments. Different mechanisms of C. sachalinensis Kom. seedlings responding to water stress in different extents were compared and analyzed. 【Result】 Seedling growth and respiratory metabolism were both badly influenced by continuous drought and waterlogging stresses. Root activities were badly restrained after 1-day drought, but rapidly depressed after 3-day waterlogging. The roots respiratory rates under drought stress were firstly increased then rapidly dropped, and the peak value appeared at 5 d. However, the respiratory rates hardly changed at the first five days of waterlogging and then decreased. The root biochemical respiratory pathways and electron transfer pathways were not changed significantly under 1-day water stress, and then the percentages of TCA and CP dropped sharply, PPP and AP became the leading way. After 7-day water stress, the proportions of each pathway were all decreased greatly. Root respiratory metabolisms were badly checked. The key enzyme activities of TCA pathway such as SDH were reduced whereas the key enzyme activities of PPP pathway such as G-6-PDH were induced under drought and waterlogging stress in some extent. Tolerance to drought and waterlogging of seedlings stretched to the limit after 7 days of treatment. Each key enzyme activity and the regulation were greatly declined. The respiratory substrate contents such as soluble sucrose and starch and the respiratory intermediate products pyruvic acid were firstly increased and then rapidly dropped during the water stress. However, the citric acid contents were continually decreased. Moreover, continual drought and waterlogging stress reduced the Fv/Fm value in leaves and the dry matter accumulations of plants and obviously restrained the photosynthesis.【Conclusion】At the beginning period of water stress, C. sachalinensis Kom. seedlings could adapt ill environments through regulating the key enzyme activities such as SDH and changing the proportions of respiratory pathways, which adjusted the consumptions of respiratory substrates and formations of respiratory intermediate products. Seedlings under waterlogging had a lingering responses than drought. The physiological metabolisms of seedlings such as root respiration and leaf photosynthesis were all greatly influenced by continuous water stress.

Key words: Cerasus sachalinensis Kom., water stress, respiratory metabolism