Effects Of Light Intensity,CO₂,Nutrient Solution Regulation On Lettuce And Tomato Growth In Plant Factory

A plant factory was an efficient agricultural system controlled by automatic and high-precision on environmental parameters such as temperature,humidity,light and CO₂concentration,which could achieve anniversary continuous production of the crop without the influence by the external environment.Its characteristics were intelligent,three-dimensional which provided crop growth with appropriate temperature,humidity,light and CO₂.CO₂ was a raw material for photosynthesis of plants,and light was the energy source for photosynthesis of plants.In the production of plants and other facilities,CO₂ and light sources limit the photosynthesis of plants,resulting in a decrease in the accumulation of photosynthetic products.Facility agriculture light-supply system,CO₂ gas application,and nutrient solution management are of vital importance in the management of facility agricultural production.In this study,（1）Lettuce was used as a material to study the effects of light intensity and CO₂concentration on the growth of lettuce,and the carbon fixation effect of carbon fixation in facility agriculture was initially explored;（2）Tomato was used as a material to increase the light intensity and CO₂ respectively.Nutritional liquid formulations in the regulation of plant management on tomato growth,quality,photosynthetic characteristics,fluorescence characteristics.The main results and conclusions of this study are:1、The results indicated that doubled CO₂ concentration is beneficial to improve the plant height,stem diameter,number of leaves,root length,leaf width,maximum leaf area.Moreover,they were positively correlated with doubling times.The photosynthetic characteristics（Pn,Ci,Gs,Tr）of lettuce increased with doubling times,but Ls decreased.The daily average assimilation rate A increased first and then decreased,while the 30ds average daily assimilation rate A of C1(800μmol·mol^-1CO₂)and C2(1600μmol·mol^-1CO₂)increased by 28.76%and 37.55%respectively over CK.The GR of C1 and C2 successively increased by 25.86%and 42.78%significantly.Doubled CO₂ concentration increased lettuce biomass,improved nutrient content so that the quality was improved.Simultaneously,C1 and C2respectively increased the utilization of light energy of lettuce by 28.51%and 40.13%significantly.2、The study showed that the plant height,stem diameter,leaf number and maximum leaf area of lettuce were significantly higher than CK.With the increase of CO₂ concentration,the plant height and the maximum leaf area increased first and then decreased.The plant height was the highest at 1600μmol·mol^-1CO₂（T3）,and the maximum leaf area was the highest at1200μmol·mol^-11 CO₂（T2）;stem diameter and leaf numbers were increased with the increasing CO₂ concentration;in addition,lettuce yield showed a steady upward trend,but the growth rate gradually decreased with the increase of CO₂ concentration.With the increase of CO₂ concentration,the yield of lettuce increased,and the contents of soluble protein,vitamin C,reducing sugar and nitrate of lettuce leaf increased.The total soluble sugar content increased first and then decreased.Carbon sequestration increased with increasing CO₂concentration.The increase of CO₂ promotes the growth of lettuce and increases lettuce yield,quality and carbon sequestration.3、The plant height decreased,stem diameter increased significantly,leaf length and leaf width decreased significantly,and both leaf number and root length increased first and then decreased with increasing light intensity under the condition of CO₂ enrichment.The lettuce yield increased first and then decreased with the increase of light intensity.Among them,L2was significantly higher than L1 and L3.The underground dry fresh weight showed an upward trend.The difference in underground fresh weight was not significant.The L3underground dry weight was significantly higher than L1 and L2.The ratio increases with increasing light intensity,but the difference is not significant.Chlorophyll a,chlorophyll b,carotenoids,and chlorophyll（a+b）all increased with light intensity,but the difference was not significant.Chlorophyll a/b showed a downward trend with increasing light intensity,but the difference was not significant.The net photosynthetic rate Pn showed L3>L2>L1,and the difference was significant.Ci,Gs,Tr all increased with the light intensity,and the difference was not significant.The stomatal density increases as the light intensity increases.The results of this study show that under the condition of CO₂ enrichment,increasing the light intensity can promote lettuce morphogenesis and lettuce seedling growth,promote lettuce growth,increase lettuce yield,and increase lettuce carbon sequestration.The dry matter accumulation and carbon fixation of L2 were the highest,and the most suitable light intensity(60%middle light,175±2μmol·m^-2·s^-1)was the best in all treatments.That is,the increase of light intensity is conducive to the growth of lettuce,and the comprehensive yield factor is L2 under the condition of CO₂ enrichment.4、In the process of the influence of light intensity,CO₂,and nutrient solution on tomato growth,three light intensity treatments（low light intensity L1,medium light intensity L2,and high light intensity L3）,Hoagland and Yamasaki are two levels of nutrient solutionand elevated CO₂ and ambient CO₂ were set.The growth of tomato was evaluated comprehensively by tomato growth index,EC value of nutrient solution,tomato yield and quality.The results of this study show that increasing the light intensity can reduce the plant height,increase the stem diameter,and increase seedlings.It is beneficial to provide preliminary photomorphogenesis for the accumulation of photosynthetic products,increase fruit yield and improve tomato quality.CO₂ enrichment increased stem height,reduced leaf area,and increased yield.Nutrition can promote the increase of soluble solids and help improve quality.From the viewpoint of yield,C1L3H is optimal,and C1L2H and C1L2Y are superior.From the standpoint of quality,C1L2H and C1L3H are superior.Due to the high light intensity and the tendency of leaf curling during the experiment,the nutrient solution has a large demand and consumes much energy.Considering comprehensive consideration,it is most suitable to enrich the light intensity Hoagland nutrient solution in L2 medium with CO₂enrichment.The results of this experiment show that it is appropriate to use a nutrient solution with a low nutrient content under low light intensity conditions.In summary,this study shows the optimun CO₂ concentration were 1200μmol·mol^-11 and light intensity were(175±2μmol·m^-2·s^-1)for lettuce growth in plant factories.The most suitable parameters for tomato growth in the plant factory were the light intensity of(340±2μmol·m^-2·s^-1)and Hoagland nutrient solution.The most suitable parameter for tomato growth was the light intensity of(175±2μmol·m^-2·s^-1)and Hoagland nutrient solution in the plant factory under CO₂ enrichment.