Research On The Growth Of Brassica Napus L.Seedings In Plant Factory Based On Light And Temperature Regulation

Light and temperature are two main environmental factors during the plant life,which plays a vital role on plant growth and development.Effects of light and temperature on plant growth and development have a coupling relationship,sometimes complementary,and sometimes mutually inhibited.Rape(Brassica napus L.)is major oil crops in China,healthy seedling growth of rape seedlings directly affects the yield and quality of rape seed.In this paper,rape cultivar,cv.Nannongyou 4,was selected as test materials.Modulating spectral energy distribution of LEDs and using airconditions to control temperature,we studied effects of different light quality and light intensity on rape seedling growth and effects of different temperatures on rape seedling growth.Optimizing light and temperature parameters,we explored the effects of light and temperature coupling on rape seedling growth.The aim was to find an optimized light and temperature parameters to ensure healthy growth of rape seedlings and reduce energy consumption in plant factory.The main results and conclusions are as follows:1.Light quality regulated the growth of rape seedlings.There were no significant differences of plant height,leaf area and fresh weight of seedlings in all treatments,but dry mass of plant under RBG was significantly greater than that of other treatments.Chlorophyll(a+b)of RB,RBY and CK treatments were significantly greater than that of RBG and RBW treatments.Stoma of RB treatment was the most,and leaf thickness and palisade tissue of RB and RBW treatments were significantly higher than other treatments.MDA content under RB was minimum,and there was no significant difference with RBG treatment.CAT activity of RBY treatment,POD activity under RBG and SOD activity of RBW treatment were the highest.The results suggested that RBG light was conducted to accumulate more dry matter of rape seedlings,supplement other spectrum based on combination of red and blue light did not affected fresh mass of rape seedlings.2.Light intensity regulated the growth of rape seedlings.With the increase of light intensity,rape seedlings gradually grew better,and plant height,stem diameter,root length,leaf area and dry matter increased.Photosynthetic pigment contents of RB400 and CK treatment were significantly less than those of RB300 and RB200 treatments;Ci,Gs,Tr of RB300 treatment were significantly higher than other treatments.Pn of RB400 treatment was significantly higher than other treatments,which related with well-development leaf structure,including palisade tissue,spongy tissue and chloroplast structure.While the mesophyll cells of RB200 treatment were disorders,and chloroplast developed round,some lamellaes were broken and unclear,which affected the growth of plant.The results showed that rape leaves of RB400 treatment developed well,which was beneficial to photosynthesis.Compared with 300?mol m-2 s-1 and below,400?mol m-2 s-1 combination of red and blue light was more conducive to growth of rape seedlings.3.The plant height and total dry matter were increased with the increasing of temperature.Total dry mass of T4 treatment was significantly greater than that of T1 and T2 treatments,and had no significant difference in fresh shoot of T2,T3 and T4 treatment,while total fresh weight of T2 and T3 treatments was significantly greater than T4 treatment.The lower temperature,the larger Stoma area,but stomatal aperture increased with the increasing of temperature.Leaf thickness of T3 treatment was significantly greater than T1 treatment,while the length of the palisade and spongy tissue were significantly larger than the other treatments.The soluble protein content of T3 treatment was the highest,and sucrose content of T4 treatment and the starch content of T1 treatment were significantly greater than the other treatments.SOD and CAT activity increased with the increasing of temperature,antioxidant enzyme activities and MDA content of T4 treatment were significantly higher than other treatments.The results suggested that the lower temperature in daytime inhibited seedling growth,moderate temperature(22? and 25?)in daytime was in favor of shoot of rape seedling growth,especially at 25? of day temperature was beneficial to leaf development.4.Change of light and temperature conditions didn't significantly affect stem diameter,root length and photo synthetic pigment content of rape seedlings.Plant height of L1T2 treatment significantly higher than that of the other two treatments.Leaf area gradually increased with the increasing of temperature and light intensity,and the total dry mass of L2T3 treatment was significantly greater than that of L1T2 treatment.Dry mass of L1T1 treatment was minimum.Soluble sugar content of L2T3 treatment significantly was greater than that of the other two treatments.Soluble sugar and sucrose content increased with the rising of temperature,on the contrary,starch content reduced.Higher light intensity made the area of stomata increased and stomata open,but the number of stomata reduced.In addition,the leaf thickness,palisade tissue thickness and the ratio of palisade and spongy tissue of treatment L1T2 were significantly greater than those of the other two treatments,and of the treatment of L1T1 were the smallest.The result suggested that daily temperature in the range from 19? to 28?,light intensity below 400?mol m-2 s-1,light intensity was an important limiting factor for rape seedling growth,lower light intensity and lower temperature prohibited the seedling growth,rising temperatures could promote rape seedlings growth to make up for inhibition due to shortage of light energy.