Abstract: Under controlling temperature and light intensity conditions ， the temperature compensation point (TCP)and the star time of photosynthesis(STP) of cucumber leaves have been studied by nsms a CIRAS-1 portable photosynthetic instruments which manufactured by PP system company of England．The results showed that the TCP of cucumber leaves 3.3℃ at low temperature(3—15℃ and 400 μmol·m ^-2·s PFD)and 48.9—50.7℃ at high temperature(40—48℃ and 1300 μmol·m ^-2·s PFD)respectively． efect of low temperature
0n TCP in diferent cucumber varieties was smal1．TCP of CV.‘Xintai mici’，a solar greenhouse variety，was relativelv lower at high temperature than that of the ‘Jinyan 4’， an open-field variety． The TCP of cucumber of old
leaf Was higher than that of young leaf under low temperature．Generally，the stal~time of photosynthesis(namely，Pn from zero to maximum) in cucumber functional leaf was 42—45 min，but that in old lear was 54—60 min．

Key words: Cucumber, Temperature compensation point of photosynthesis, Start time of photosynthesis, Stomata conductance