| Plant growth and development must rely on sunlight,air,temperature,water and fertilizer,and the light is one of the key regulators.However,the mechanism of plant growth and development with different light quality is different.New Light source LED(Light emitting diodes)is not only a kind of energy-efficient Light source,which can launch monochromatic Light and combine several Light,but also the best Light to study the influence of Light quality of plant growing development.To clarify the best harvesting time and screening the best mass ratio of optimal LED light quality,this study adopt W?B?R?Y?G?P?9R/1B?4R/1B?36R/9B/5Y and 36R/9B/5P as light source material,use leaf lettuce which is named "large American fast growth" as the test materials.The following results were obtained by determining the growth and physiological characteristics,fluorescence parameters and nutritional quality:1?The light which combined by red,blue,and yellow light can promote the growth of lettuce;Besides,the red,yellow and green light can significantly increase plant height,while blue light can increase stem diameter and above ground fresh weight after the lettuce planted 25 days.2?Both blue and red light can increase the content of anthocyanins,soluble proteins and total phenols.Blue light reduces nitrate and soluble sugar content,while red light can increase soluble sugar content.To a certain extent,yellow light can respectively Inhibition the nitrate accumulation promoted and increase the total phenolics content.In addition,violet and blue light also promoted the increase of flavonoid content.The above results all performed best after the lettuce colonized 25 days.Under red-blue composite light,the quality of lettuce can be effectively improved,while to some extent,the light combined by red,blue,and yellow light is not conducive to the improvement of lettuce's quality.3?The red,blue,and yellow composite light can effectively promote the accumulation of chlorophyll and carotenoids in lettuce,increase the net photosynthetic rate,the transpiration rate and the water loss of the lettuce's leaf,and decrease the stomatal conductance which is not beneficial to the open of stomata,besides,it also reduces the intercellular CO2 concentration and therefore can increase the CO2 utilization efficiency of lettuce mesophyll cells.4?Compared with white light,ABS/RC,TRo/RC,ETa/RC,and DIo/RC increase significantly under red,blue,and yellow composite light.For the initial fluorescence Fo and maximum fluorescence Fm under red,blue,and yellow composite light : It is conducive to its increase in earlier growth stage,but obviously promote the increase of them in the later.Yellow or purple light with both red and blue light can also increase Fv/Fm,maybe this means the PSII reaction center energy capture efficiency of the combination of two groups with light leaves is relatively high(Rodriguez et al.,2007).There is no significant difference between q P,NPQ and control with white light under each compound light,this indicated that only a small part of the light energy absorbed by the leaves cannot be used by photosynthesis for dissipated as heat.5?red light significantly promoted the activity of SOD,POD and CAT,and red-blue composite light had a positive effect on the activity of SOD and POD in lettuce;Blue light promoted the activity of GOGAT,and each light quality was conducive to GOGAT activity in the late planting stage.Green and red-blue light 9:1 can effectively improve GS activity,red and blue light 9:1 can increase the activity of GDH.Red-blue,red-blue-yellow,and red-blue-violet combined light can all increase the activity of NR,while red-blue-yellow combined light inhibited the increase of Ni R activity.In summary,the best harvest time for leaf lettuce is 25 days after planting,for improving the quality of lettuce the red-blue combined light was better,while for the physiological characteristics such as photosynthetic and chlorophyll fluorescence parameters of lettuce,the red-blue-yellow combined Light is good. |
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