Abstract: Abstract：The effects of different photoperiod（12，14，16，18 and 20 h · d-1）on growth of cucumber
and tomato seedlings were studied.The relationship between the growth differences and endogenous
hormones（ZT，IAA）was discussed.The results indicated that the extented photoperiod could significantly
decrease the plant height of cucumber and tomato seedlings and promote the content of soluble protein and
soluble sugar of tomato seedlings.Under the treatment of 16 h · d-1 photoperiod，the leaf area reached to
maximum and the healthy index significantly higher than the treatment of 12 h · d-1 and 14 h · d-1，but had
no significant differences compare with 18 h · d-1 and 20 h · d-1 photoperiod.With the extension of the
photoperiod，the ZT and IAA contents of tomato seedlings increased gradually in leaf and decreased
gradually in stem，and it had linear regression correlation with leaf area and plant height. The IAA and ZT
contents had linear regression correlation with plant height and leaf area respectively of cucumber
seedlings. Overall，16 h · d-1 photoperiod was more beneficial to the growth and cultivated health seedling
of cucumber and tomato plants. Photoperiod may affect the growth and development of cucumber and tomato
seedlings by regulating the endogenous ZT and IAA contents.

Key words: tomato, cucumber, seedling, photoperiod, ZT, IAA, correlation