Abstract:
【Objective】The study was conducted to clarify the effect of the different ages of transplanted cucumber seedlings on their growth physiology and yield in substrate cultivation,screening out the suitable age for cucumber seedling transplanting under substrate cultivation conditions.【Method】Cucumber （cv.Xinchun No.4） was employed as the experimental materials.Four treatments of seedling ages were set,i.e.,T
1 （four-leaf growth stage）,T
2 （three-leaf growth stage）,T
3 （two-leaf growth stage） and T
4 （one-leaf growth stage）.The plant height,stem diameter,root activity,chlorophyll content,photosynthetic parameters,fluorescence parameters and yield of the cucumbers transplanted at different seedling ages were measured.【Result】The plant height of cucumber in T
3 treatment was significantly higher than that of the other three treatments.The plants of T
3 had the largest root volume,which was significantly increased by75.86%and 36.00%compared with T
1 and T
2.Root vitality was the largest in T
4 treatment.The net photosynthetic rate （P
n） and stomatal conductance （G
s） of T
3 treatment were significantly higher than those of the other three treatments.Compared with T
1,T
2,and T
4,the P
n was increased by 24.34%,14.23%,6.04%,and the Gs was increased by 60.73%,21.45%and 14.59%,respectively.The transpiration rate was also the highest in T
3 treatment,which was significantly increased by 71.16%and 20.27%compared with T
1 and T
2,while the intercellular carbon dioxide concentration （C
i） in T
3 was the lowest among the four treatments.The maximum photochemical efficiency （F
v/F
m） was the largest in T
4,followed by T
3 treatment.Compared with T
1 and T
2 treatments,the F
v/F
m for T
3 was significantly increased by 1.29%and0.84%,respectively.The actual photochemical efficiency （ΦPSⅡ） was the largest in T
3,followed by T
4,and both T
3 and T
4 were significantly higher than T
1 and T
2 treatments.Compared with T
1,T
2 and T
4,the photochemical quenching coefficient （qP） of T
3 was increased by 2.95%,1.40%and 0.84%,respectively.The non-photochemical quenching coefficient （NPQ） was the smallest in T
3 treatment.In terms of dry matter,the leaf dry weight of T
3 was significantly higher than that of the other three treatments.The fruit dry weight of T
3 was also the largest,which increased by 71.43%,30.78%and 15.07%,respectively,relative to T
1,T
2,and T
4 treatments.In terms of yield,both the fruit weight per plant and the yield per mu for T
3treatment were significantly higher than those of the other treatments.Compared with T
1,T
2,and T
4,the yield of T
3 increased by 49.11%,37.17%,and 6.08%,respectively.【Conclusion】Under the condition of substrate culture,the growth status,photosynthetic fluorescence characteristics and the yield of the cucumber plants were better when transplanted at the two-leaf stage than other treatments,which therefore could be the optimum stage of cucumber seedlings transplanting.
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