Effect Of Daily Light Integral On Seedling Of Tomato And Cucumber In Plant Factory

Artificial light plant factory become widely concerned to cultivate plants due to the advantages of environment controlled,sterile and high efficiency.Vegetable seedlings have the characteristics of small plant type,short period and sensitive to environment,suitable for cultivation in artificial light plant factory.Light source is one of the main sources of energy consumption.Electing suitable illumination parameters can not only improve seedling quality,but also save energy consumption.The integrated photosynthetic photon flux density?PPFD?received during a 24-h period is called the Daily light integral?DLI?.The unit is mol·m^-2·d^-1.Experiment divided into two parts,firstly,put seedlings of tomato and cucumber under different DLI treatment respectively and explored growth and development of seedling of tomato and cucumber to choose optimal DLIs;Secondly,under the conditions of optimal DLI,the effects of different illumination strength and time on the seedlings of tomato and cucumber were investigated,and the optimal strength of illumination strength and time were further determined.The results were as follows:1.Tomato seedling test:?1?The optimal DLI of tomato seedlings was 13 mol·m^-2·d^-1.The growth and morphology of tomato seedlings was different under different DLI conditions.In a certain range,enhancing DLI was conducive to the morphologic formation and growth of tomato seedlings,and under a DLI about 13 mol·m^-2·d^-1 with a large amount of biomass accumulation and high-quality seedling quality.In terms of physiological indexes,soluble sugar increased with DLI enhancing,but soluble protein gradually decreased under higher DLI.Root activity increased first and then decreased with the rose of DLI,reached the maximum at 11.5 mol·m^-2·d^-1.As DLI goes up,the activity of antioxidant enzyme was improved,and the content of photosynthetic pigment decreased.The results showed that the flower was well developed within DLI ranging from 11.5 to 14.3 mol·m^-2·d^-1.?2?Under the condition of optimal DLI(13 mol·m^-2·d^-1),the optimal illumination intensity was 200²30?mol·m^-2·s^-1,and the optimal illumination time was 16¹8 h.The two treatments?T1 and T2?of low light intensity and long illumination time were more conducive to the accumulation of tomato seedling dry weight and fresh weight,and had higher seedling index and thicker blade.In terms of physiological indexes,soluble protein had a higher level in the treatment of low light intensity+long illumination time.The photosynthetic pigments under the treatment of low light intensity and long illumination time were higher,and the PSII activity and the photochemical efficiency was higher at the same time.2.Cucumber seedling test:?1?The optimal DLI of the cucumber seedlings was 6.4 mol·m^-2·d^-1.The increase of DLI promoted the growth of the underground part of cucumber seedling and inhibited the growth of the above ground part,which increased the biomass distribution ratio in the underground part.At the same time,the dry matter rate increased slowly with the increased of DLI,and the thickness of cucumber leaves increased first and then decreased.In terms of physiological indexes,the soluble sugar content was positively correlated with DLI,and soluble protein increased first and then decreased.With the increase of DLI,the activity of SOD showed an upward trend.Under the condition of low DLI,chlorophyll content was higher and chlorophyll a/b was lower.In the later stage of the flowering,it was found that when the seedling DLI was 6.4 mol·m^-2·d^-1,the flowers developed best,so 6.4 mol·m^-2·d^-1was chosen as the optimal DLI for cucumber seedlings.?2?Under the condition of optimal DLI(6.4 mol·m^-2·d^-1),the optimal illumination intensity was 110¹25?mol·m^-2·s^-1,and the optimal illumination time was 14¹6 h.The combination of low light intensity and long duration is more conducive to the accumulation of underground growth of cucumber and whole plant dry matter,with a relatively high seedling index and thicker leaves.In terms of physiological indexes,the young seedlings treated with low light intensity and long duration had higher soluble sugar content,higher PSII activity,and higher photochemical efficiency.