| To better understand effect of irrigation treatments, morphological and ecophysiological responses of Camellia oleifera'Lu Shan Snow'and Camellia 'Winter's Snowman'(C. oleifera×C. sasanqua) seedlings under irrigation levels at 0.11 0.22,0.33, or 0.45 m3·m-3 volumetric water content (VWC,θ) and a manual irrigated group (K group) were investigated from July to December 2009. Results indicated that:irrigation levels had significant influence on plant morphological growth, water relations, photosynthesis and water use efficiency changes.Maximum value of branch length, branch number, leaf number, plant height and root length of'Lu Shan Snow'were 7.99cm,2.625,27.63,17.50cm and 24.11cm, minmum value were 4.01cm,-2.125,-18.63,-19.35cm and 21.83cm. Morphological growth of'Lu Shan Snow'had inflexion, after the irrigation treatment reached 0.339 m3·m-3, the branch length, branch number, leaf number and plant height could hardly grow further even irrigation level rised. Under drought stress (0.113 and 0.226m3·m-3 treatments), branch length, branch number, basal diameter, leaf number increment, root length and dry weight decreased without exception, but root length increased. Positive correlations were found between irrigation treatments and plant growth of 'Winter's Snowman'; to'Lu Shan Snow', irrigation treatments either too low or too high would restrain its growth.Values of midday water potential were-1.83,-1.50,-1.33,-1.51 and-1.38MPa for'Lu Shan Snow'corresponding to five irrigation levels, and-2.08,-1.70,-1.86,-1.75 and-1.41 for'Winter's Snowman'; water potential of'Winter's Snowman' was highly correlated with irrigation treatments and had significance among treatments, mean while, irrigation change couldn't make obvious influence on that of 'Lu Shan Snow'. Under most conditions, every term of water potential of'Winter's Snowman'was lower than that of'Lu Shan Snow'PSⅡphotochemical convertion efficiency of'Lu Shan Snow'was higher than that of'Winter's Snowman'. Fv/Fm values were 0.58,0.69,0.72 and 0.72 (without 0.113 m3·m-3 treatment) for'Lu Shan Snow', and 0.72,0.63,0.62,0.67,0.71 and 0.72 for'Winter's Snowman'corresponding to irrigation levels; T1/2 values of'Lu Shan Snow'were 33.28,12.07,22.175,23.54 and 21.91ms, and 5.37,6.95,7.89,9.95 and 10.61ms for'Winter's Snowman'. Fo values of'Lu Shan Snow'were 179.38, 156.57,131.88,121.39 and 104.80, and 148.87,159.41,132.75,147.96 and 117.91 for'Winter's Snowman'; when apposed in drought condition, Fo of'Lu Shan Snow' increased greater than that of'Winter's Snowman'. Fm of'Lu Shan Snow'first increase then decrease by the irrigation improved, the values were 442.53,511.05, 479.04,436.19 and 380.93; Fm of'Winter's Snowman'was increased by the irrigation improvement at all time, the values were 419.68,441.07,414.35,513.00 and 420.07. Apparent quantum effieciency of'Lu Shan Snow'was higher than hat of 'Winter's Snowman':the AQE values were 0.027,0.018 and 0.022 (without 0.113 m3·m-3 treatment) for'Lu Shan Snow', and 0.011,0.020,0.015 and 0.008 for 'Winter's Snowman'. Light saturation point of both cultivars was around 400μmol·m·-2·s-1, and no significant difference was found among cultivar and treatments. Stomatal conductance value of both cultivars was siginificantly correlated with irrigation levels, and has significant effect on photosynthesis and transpiration.Water use efficiency of both cultivars reached their peak value when irrigation level rised to 0.339m3·m-3 VWC, then with the irrigation level up, water use efficiency decreased. The maximum WUE value was 12.29μmol CO2/mmol H2O for'Lu Shan Snow'and 19.76μmol CO2/mmol H2O for cultivar'Winter's Snowman'.Generally speaking, Camellia'Winter's Snowman'was still growing quite vigorous even when irrigation level is high, however, growth of Camellia oleifera 'Lu Shan Snow'reached a certain level then, no more advance. Under relative high irrigation conditions, growth of'Lu Shan Snow'was weaker than that of'Winter's Snowman'; under lower irrigation conditions, ther growth had a little difference, but 'Lu Shan Snow'had a higher mortality.
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