| This study aimed to investigate the integrative effects of CO2 concentration(500,1000 and 1500?mol mol-1),light intensity(100,200 and 300?mol m-2 s-1)and air velocity(0.25,0.50 and 0.75 m s-1)on the thermal exchange(sensible heat flux and latent heat flux),gas exchange(photosynthesis and transpiration),growth and tipburn occurrence of indoor cultured lettuce.During the experiment,the air temperature inside the plant factory was maintained at 24/20?,while the relative humidity was maintained in the range between 60%and 70%.In evaluating the relationship between the independent and dependent variables,a correlation analysis was performed.Moreover,an effect size test,with a small effect size of 0.0%-20%,a medium effect size of 20%-50%and a large effect size of more than 50%was used to assess the magnitude of one-way effects,as well as the two-and three-way interactions.On the other hand,a multi-fan system(MFS)for a single culture bed was developed to improve the airflow in the plant factory.The MFS has seven small fans to generate airflow from two horizontal opposite directions.Four fans were mounted on the front side and three fans on the backside of each culture bed.The obtained results were summarized in three main chapters as follows:Lettuce plant growth and tipburn occurrence as affected by airflow using a multi-fan system in a plant factory with artificial light.This study aimed to investigate the effect of airflow on the growth and tipburn occurrence of indoor cultured lettuce.Under a light intensity of 200[imol m-2 s-1 and a CO2 concentration of 1000 ?mol mol-1.three airflow patterns were evaluated:T1)both the front and back sides of the culture bed were air inlets;T2)the front side was an air inlet,while the backside was an air outlet;and T3)both the front and back sides of the culture bed were air outlets.A culture bed without MFS was used as a control(T4).The effect of air velocity on the sensible heat flux(Sh),latent heat flux(Lh,)and leaf boundary layer resistance(1/gbv)was also investigated.The results showed that the flow pattern in T1 improved the airflow with an average air velocity of 0.75 m s-1 compared to 0.23 n s-1 in T4.The high air velocity in T1 reduced the 1/gbr by 46%compared to that in T4.The decrease in the 1/gbv in T1 was accompanied by an increase of 45%and 33%in the Sh and 49%and 42%in the Lh,compared to those in T4 during the light and dark periods,respectively.The fresh and dry weights of lettuce plants in T1 were 1.13 and 1.06 higher than those in T4,respectively.No tipburn was observed on lettuce plants grown under the MFS,while 5 leaves per plant were injured with tipburn in T4.Integrative effect of CO2 concentration,light intensity and air velocity on the sensible and latent heat fluxes of lettuce plants grown under artificial light.This study aimed to investigate the effect of various combinations of CO2 concentration,light intensity and air velocity on the sensible heat flux(Sh),convection regime(CR)and latent heat flux(Lh)of indoor cultured lettuce.Based on the results obtained,the Sh and Lh increased by 30.8%and 36.7%with an increase in light intensity from 100 to 300 ?mol m-2 S-1,with effect sizes of 16%and 40%,respectively and 45.3%and 44.1%with an increase in air velocity from 0.25 to 0.75 m s-1,with effect sizes of 33%and 26%,respectively.No unique relationship was found between CO2 concentration and Sh,while Lh increased by 17.1%when CO2 concentration increased from 500 to 1000 ?mol mol-1.The correlation between CR and light intensity yielded a positive slope,while air velocity yielded a negative slope,with an effect size of 74%.Accordingly,forced CR was dominant between lettuce plants and the surrounding air.The occurrence of tipburn in lettuce plants was significantly related to light intensity,with an effect size of 42%.The highest number of lettuce leaves injured with tipburn of 6 leaves/plant was observed at a light intensity of 300 ?mol m-2 s-1.Conversely,tipburn occurrence decreased by 84.4%,with an increase in air velocity from 0.25 to 0.75 m s-1.The interaction between light intensity and air velocity significantly affected the Sh,Lh and tipburn occurrence,with effect sizes of 10%,90%and 22%respectively.Lettuce plant growth,gas exchange and light use efficiency as affected by the interactive control of CO2 concentration,light intensity and air velocity in a plant factory with artificial light.This study aimed to investigate the effect of various combinations of CO2 concentration,light intensity and air velocity on the growth,photosynthesis,transpiration,stomatal conductance and light use efficiency of indoor cultured lettuce.The results showed that the fresh and dry weights of lettuce plants were significantly affected and positively correlated with CO2 concentration(effect sizes of 86%and 43%,respectively)and light intensity(effect sizes of 93%and 89%,respectively).An increase of 35.8%and 48.9%in the shoot fresh and 30.0%and 58.6%in the shoot dry weight were observed with an increase in CO2 concentration from 500 to 1500?mol mol-1 and light intensity from 100 to 300?mol m2 s-1,respectively.Air velocity showed a small effect size on the growth,transpiration and stomatal conductance of lettuce plants.However,photosynthesis was positively correlated with CO2 concentration,light intensity and air velocity(effect sizes of 74%,97%and 40%,respectively).The increase in light intensity from 100 to 300?mol m-2 s-1 increased the transpiration and stomatal conductance by 34.9%and 42.1%,respectively(effect sizes of 67%and 60%,respectively),whereas the increase in CO2 concentration from 500 to 1500 ?mol mol-1 decreased the transpiration by 15.3%(effect size of 23%).Furthermore,a decrease in stomatal conductance of 40.9%was observed when CO2 concentration was increased from 1000 to 1500 ?mol mol-1.The most influential two-way interactions were observed between light intensity and CO2 concentration on the fresh and dry weights of lettuce shoot,photosynthesis,transpiration and light use efficiency(effect sizes of 31%to 42%),as well as between light intensity and air velocity on photosynthesis(effect size of 56%).A small effect size was observed for the three-way interaction on the shoot fresh weight and stomatal conductance,compared to a medium effect size on the shoot dry weight,photosynthesis,transpiration and light use efficiency. |
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