| Lettuce seedlings(Lactuca sativa L.) of two cultivars(Butter Lettuce,soft leaf, mature early and Grand Rapid,loose leaf,mature in late) was selected as material in this study by measuring lettuce seed germination,target seedling morphology, photosynthetic characteristics,chlorophyⅡfluorescence parameters and enzyme activity in lettuce seedlings to research the effect of different light qualities on physiological and biochemical indicators,and affecting mechanism by using the LED light sources leaf.And the same time,the differences of two lettuce cultivars are comparied.The main experimental results are as follows:1.Under the LED light sources condition,the effect of the different light qualities on the seed germination was investigated.The results showed that light quality treatment of using LED light source promoted the seed germination of lettuce. Different effects of seed germination were showed among the different monochromatic light qualities.Especially that lettuce variety which had bad germination situation showed seed sprouting quickly and neatly,good growth,by treating under the LED-B.After light quality treatment,there was no significant difference of seed germination rate from the fluorescent(F) treatment.2.Light quality increased plant height of lettuce seedlings,especially LED-R＞F (CK);The main effect of LED light on the root length of lettuce seedlings performanced best with the short wavelength which under light treatment(LED-B); but under the LED-B,the number of lettuce leaves was the least;deal with the different varieties of lettuce seedlings by using fluorescent lamps,the top dry and fresh weight were largest;the ratio of root to top under the fluorescent lamps had the maximum value.It concluded that monochromatic LED light sources of different light qualities plays a different role in the course of lettuce seedlings growth,the role of superposition through different light qualities exhibited well in the control treatment.3.LED-R significantly increased the chlorophyⅡb contents of lettuce seedling leaves.The the chlorophyⅡcontents of Butter Lettuce was more than that of Grand Rapid under each light quality treatment.And the value of chlorophyll a / b in Grand Rapid was at around 2.3,which was higher than that of the corresponding light quality treatment for the Butter Lettuce.The light quality impacted the requirement of leaves optical properties of different lettuce varieties.4.The highest Pn was exhibited in Butter Lettuce under the LED-B.Gs are maximum under LED-R:B.Ci is the largest under the LED-B.These results showed that the LED-R:B light treatment increased leaf stomatal conductance,and especially increased the potential efficiency for solar energy utilization of lettuce seedlings.With the treatment of LED light quality,Gs and Ci were increased,indicating that non-stomatal factors are the reasons for the inhibited photosynthesis.5.Among the light quality treatment,there was no significant differences of the Fv / Fm,and was the largest under the LED-B.It can be concluded that the light quality played the important role on the photosynthetic efficiency and the change of chlorophyⅡfluorescence parameters.6.The highest SOD activity under the LED-B;LED-B can enhance the activity of CAT,and the lowest activity under the red light;the POD activity of Butter Lettuce was the highest in control treatment.While under the different light qualities of LED light sources,the same enzyme activity maintained a relatively low level.But the red light will be able to greatly enhance the activity of the POD in Grand Rapid.In the same treatment of light quality,the varieties of the lettuce performanced the differences responses. |
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