| Light is one of the critical environmental factors affecting the growth and development of plants,as it serves as the primary energy source for photosynthesis in plants,which mainly acts through light quality,intensity and photoperiod.Although LEDs are most widely used in plant factories,the unreasonable lighting patterns and high energy consumption during growth have become bottlenecks that restrict the development of plant factories.Therefore,choosing the appropriate light pattern is an important means to promote vegetable growth and improve energy use efficiency.In this study we investigated the effects of various combinations of red,blue and white light qualities on the morphogenesis and photosynthesis of‘Hongqijian’sweet pepper seedlings.Then,we examined the impact of daily light integral(DLI)on the growth and energy consumption of sweet pepper seedlings.Finally,we further explored the effects of intermittent light supplementation during the dark period on the cultivation of strong sweet pepper seedlings.This study aimed to identify the suitable light pattern for the growth of sweet pepper seedlings to achieve the purpose of saving cost and increasing efficiency of vegetable seedling cultivation.The main research findings are as follows:1.In our previous research,we screened the red and blue light quality ratio of 3:1(3R1B)suitable for the growth of sweet pepper seedlings.Therefore,in this study,we further added0%,20%,40%,60%,80%and 100%of white light(W)into the combination light of 3R1B.The ratios of red,blue and white light were set to CK(3R1B),Q1(3R1B1W),Q2(9R3B8W),Q3(3R1B6W),Q4(3R1B16W)and Q5(W).The results showed that adding a certain percentage of W light was more beneficial than not adding W light to cultivate strong sweet pepper seedlings,and the height,stem thickness,and P_nof sweet pepper seedlings showed a trend of increasing and then decreasing with the increment of the percentage of W light,and all of them reached the best under Q1 treatment.Moreover,their stem thickness,P_nand Chl a were significantly higher than those of CK and other treatments,and these corresponding parameters were increased by 10.09%,18.55%and 31.84%under Q1 compared with CK,respectively.Meanwhile,the light energy use efficiency(LUE)and electric energy use efficiency(EUE)of sweet pepper seedlings also reached their peak values under Q1 treatment.However,the growth and photosynthesis of sweet pepper seedlings were inhibited by increasing the proportion of W light.This suggests that the addition of W light can improve the photosynthesis of seedlings and promote their biomass accumulation,which is beneficial to the cultivation of strong sweet pepper seedlings.2.The screened light quality ratios were used to further investigate the effect of different DLI on the growth of pepper seedlings.Six DLI gradients of 9.72,10.80,11.34,11.88,12.60and 13.86 mol/(m~2·d)were calculated within the optimal range of light intensity and photoperiod for sweet pepper growth.These were designated as CK,D1,D2,D3 D4 and D5,respectively.The findings indicated that different DLI had significant effects on the growth,biomass accumulation and energy use efficiency of pepper seedlings.The stem thickness,dry and fresh matter accumulation and chlorophyll(a+b)of sweet pepper seedlings showed a trend of increasing and then decreasing with the increment of DLI,and it reached the maximum value when DLI was 12.60 mol/(m~2·d),which raised by 14.54%,127.03%,65.76%and 11.99%relative to CK,separately.However,when DLI increased to 13.86 mol/(m~2·d),the growth of sweet pepper was weakened.Interestingly,the root-shoot ratio reached its highest value at a DLI of 12.60 mol/(m~2·d)and then remained unchanged.In addition,with increasing DLI,both LUE and EUE of pepper seedlings showed a trend of increasing and then decreasing,again reaching the maximum under D4 treatment and increasing by 29.59%and 59.57%compared with CK,respectively.3.Using the screened light quality ratio and DLI,three intermittent supplementation treatments were set up during the dark period,T1(5 min of light supplementation every 1 h during dark period),T2(5 min of light supplementation every 2 h during dark period)and T3(5 min of light supplementation every 3 h during dark period),with no light supplementation during dark period as CK.The results demonstrated that the leaf area,transpiration rate and chlorophyll(a+b)of pepper seedlings increased initially and then decreased with the increment of frequency and duration of light supplementation,and compared to CK and T1,the stem diameter,plant fresh matter weight,root volume,chlorophyll(a+b)and P_nof pepper seedlings were significantly enhanced by T2 and T3 treatments,among which,T2 and T3increased by 11.78%,23.52%,20.72%,20.82%,27.34%and 6.04%,20.97%,17.57%,31.60%,39.67%relative to CK,respectively.However,there was no significant difference between T2 and T3 in terms of growth rate.Additionally,T3 had significantly lower energy consumption than that of T2 due to the short time of light supplementation.Therefore,the best energy saving effect was achieved by growing pepper seedlings in T3 under this experimental condition.In summary,under the present experimental conditions,a light pattern with light qualities of 3R1B1W,DLI of 12.6 mol/(m~2·d)and 5 min of supplemental light every 3 h during dark period was recommended for industrialized seedling production for sweet pepper. |
PDF Full Text Request