Study On The Effects Of Shade And Light Quality On The Growth And Development Of Euphorbia Pulcherrima

Three levels of shade degree(0%, 50%, 75% of full sunlight) and four kinds of light quality(white, red, yellow, blue) were set to study the effects of different light conditions on the two cultivars of Euphorbia pulcherrima (Prestige and Red Velvet). The morphological and physiological indexes relation to growth and development were measured, and blossom was also recorded. The effects of shade and light quality in the ornamental value of potted poinsettia were discussed emphatically. The results indicate:1, The effects of shade:(l)The growth of lateral shoot was inhibited under shade condition. The length of lateral shoot, shoot diameter, number and average area of leaf of Red Velvet had negativ correlation very significantly(P<0.01) with shade degree, and shoot diameter, number of leaf of Prestige had negativ correlation significantly(P<0.05) with shade degree.(2)The light saturation and compensation point of Prestige were 1545μmol/m s and13.34umol/m s;the light saturation and compensation point of Red Velvet were 1817μmol/m s and 14.75μmol/m2s. The photo synthetic rate of Prestige and Red Velvet decreased 10.1% and 24.7% under the shade degree of 50%; and decreased 61.8% and 68.6% under the shade degree of 75%. Under the shade degree of 50%, the content of chlorophyll(chl), chla, chlb were most. The content of soluble protein had negativ correlation very significantly(P<0.01) with shade degree, the content of soluble sugar had negativ correlation significantly(P<0.05) with shade degree, and the content of proline(Pro), specific leaf area(SLA) had positive correlation very significantly(P<0.01) with shade degree.(3)Shade had no effects on blooming date, but flower diameter, bract area had negative correlation significantly(P<0.05) with shade degree, and content of cyanidin had negative correlation very significantly(P<0.01) with shade degree. The ornamental value of pottedpoinsettia decreased under shade condition.(4)The shade tolerance of Prestige was bigger than Red Velvet. In this experiment, Prestig can grow and develop normally under the shade degree of 50%.2 The effects of light quality:(l)The length of lateral shoot was red > white> yellow > blue light, shoot diameter was yellow, white > red > blue light. Light quality has small effect on number of leaf, but red and yellow light could increased leaf area, while blue light could decreased leaf area.(2)The photosynthetic rate was yellow > white > red > blue light. Red, yellow blue light can induced increase of leaf chlorophyll all, but red light induced increase of chlb more, while blue light induced increase of chlb more. In the later stage, SLA was red > yellow > white > blue light; the contents of soluble protein was blue light > white > red > yellow; the contents of soluble sugar and Pro were red > blue > white > yellow light. Yellow light benefited the growth of poinsettia in the early stage, but inhibited in the later stage.(3)The plants under red light flowered 3 days later, while the plants under blue light flowered 7 days earlier than that under white light. And the yellow light had no effect on blooming date. Red light could increase the ornamental value of flower, flower diameter, bract area, content of cyanidin were all increased. Blue and yellow could decreased the ornamental value of flower, the former could decreased the content of cyaniding and the later could decreased flower diameter, bract area, content of cyanidin all.