| Rice (Oryza sativa L.)is one of the major crops in china,rice transplanting by machine is the key technology in rice production,and the quality of rice seedling is an important factor in the technology.In addition,rice-incubated under controllable artificial facilities is a new requirement due to environmental changes and other researches specific needs.Controllable artificial facilities can provide optimal conditions for cultivating rice and has an advantage in such applications as regulating planting time,researching environmental stress response,breeding and reproduction,improvement and regeneration of germplasm resource of rice.However,the favourable environmental conditions need to be established and optimized for cultivating rice in an artificial facilities.How to choose the suitable light intensity is a key factor to successfully cultivate rice under artificial light during the whole growth stages.For this reason,a variety of japonica rice was used as experiment materials in this study,in controllable chamber,we investigated the effect of light intensity on the growth and development of rice seedling and the effects of light intensities and spectral distribution on growth,photosynthetic characteristics and yield of rice.The objective of this study was to explore a suitable light intensity and spectra to cultivate rice in an indoor system.The main results of this study were as follows:1.Light intensity significantly affected the growth and quality of rice seedlings.The results showed that the plant height of RBG400 treatment was the highest in the early stage of growth,but the final plant height of each treatment had no significant difference.The stem diameters were significantly higher under RBG350 and RBG400 than that under RBG250,RBG300 and W320.The fresh and dry weights of RBG350 treatment were significantly greater than those of RBG250,RBG300 and W320.The soluble protein content of RBG350 treatment was the highest;while the soluble sugar content of RBG400 treatment was the highest.During three leaves stage,photosynthetic pigment content of RBG350 treatment was the highest,but the pigment content of RBG400 treatment was the highest during four leaves stage.The Pn,Gs,Ci and Tr of RBG350 treatment were significantly greater than those of other treatments.2.Light intensity significantly affected the growth,photosynthetic characteristics and yield of rice.The results showed that the plant heights were higher under the RBG450 and RBG650 than the RBG550 or W550 duing filling stage.The length,width,thickness and area of flag leaf and the tillers number of rice-grown under RBG550 were the greatest,and RBG550 promoted early tillering and increased the productive panicles.Net photosynthetic rate(Pn)of RBG treatments significantly increased with the increasing of light intensity,and Pn of rice irradiated with RBG increased as compared to with W550 during tillering stage,but decreased during grain filling stage,and Pn of RBG treatments didn’t significantly affected by light intensity.The Fv/Fm of rice irradiated with RBG550 was the greatest during both tillering and grain filling stages,otherwise,the panicle and grain numbers,1000-grain weight and yield were all the highest under RBG550.Maximum seed-setting rate was observed in W550 treatment.3.The spectrum significantly affected the growth and development,photosynthetic characteristics and yield of rice.The results showed that the plant height in R660+W treatment was significantly higher than that in other treatments;while plant height B460+W was significantly lower than that in other treatments.The tillers number of rice was greater under R660+W and B440+W treatments,and R660+W treatment significantly promoted tillering earlier and to effectively tiller.The plant morphology under the treatments with red light was more compact than treatments with blue light.The photosynthetic pigment content was greater under R660+W treatment,which made the leaf photosynthetic efficiency higher.During heading and filling stage,the Pn,Gs and Ci were higher under the treatments with blue light.During early stage of growth,the dry matter accumulation was more in leaf and stem-sheath,and the dry mass output and conversion percent from leaf into grains under R660+W and R630+W treatments were significantly higher than those in B460+W and B440+W treatments,but the dry mass output and conversion percent from stem-sheath into grains was higher under B440+W,and didn’t significantly differ with under R630+W.The grain weight and grain numbers of R660+W treatment were significantly higher than those of other treatments.The seed-setting rate was higher under B460+W and B440+W,but the 1000-grain weight was lighter under the two treatments,and the yield was also significantly less than that under R660+W.In summary,the low light intensity of red,blue,and green(RBG)composite light provided by light-emitting diodes(LEDs)are not conducive to the growth of seedlings,the PPFD of 350-400 μmol m-2 s-1 RBG is more suitable for cultivation rice seedlings.The PPFD of 550 μmol m-2 s-1 can better meet the light requirements of rice in whole growth stage as compared to the PPFD of 450 and 650 μmol m-2 s-1 RBG,and it will need do a further study whether white light or other wavelength light can improve the grain-filling rate of rice.In addition,longer wavelength red light supplied with white light and shorter wavelength blue light supplied with white light are conducive to the growth of rice and the formation of yield.However,the results still need a lot of experiments to verify. |
