Effects of different LEDs light spectrum on the growth,leaf anatomy,and chloroplast ultrastructure of potato plantlets in vitro and minituber production after transplanting in the greenhouse

Light spectrum plays an important role in regulating the growth and development of in vitro cultured potato(Solanum tuberosum L.) plantlets. The status of potato plantlets at the end of in vitro stage influences the minituber production after transplanting. With 100 μmol m^-2s^-1 total photosynthetic photon flux density(PPFD), a light spectrum study of 100% red light emitting diodes(LEDs) light spectrum(RR), 100% blue LEDs light spectrum(BB), 65% red+35% blue LEDs light spectrum(RB), and 45% red+35% blue+20% green LEDs light spectrum(RBG) providing illumination at the in vitro cultured stage of potato plantlets for 4 weeks using fluorescent lamp as control(CK) was performed to investigate the effects of LEDs light spectrum on the growth, leaf anatomy, and chloroplast ultrastructure of potato plantlets in vitro as well as the minituber yield after 2 months transplanting in the greenhouse. Compared to CK, RB and RBG promoted the growth of potato plantlets in vitro with increased stem diameter, plantlet fresh weight, plantlet dry weight, and health index. Furthermore, BB induced the greatest stem diameter as well as the highest health index in potato plantlets in vitro. Root activity, soluble protein, and free amino acid were also significantly enhanced by BB, whereas carbohydrates were improved by RR. In addition, thickness of leaf, palisade parenchyma and spongy parenchyma was significantly increased by BB and RBG. Chloroplasts under BB and RBG showed well-developed grana thylakoid and stroma thylakoid. Unexpectedly, distinct upper epidermis with greatest thickness was induced and palisade parenchyma and spongy parenchyma were arranged neatly in RR. After transplanting in the greenhouse for 2 months, potato plantlets in vitro from BB, RB, and RBG produced high percentage of large size tuber. BB improved fresh and dry weights of the biggest tuber but decreased tuber number per plantlet. In addition, RBG increased tuber number as well as tuber fresh and dry weight slightly. Our results suggested monochromatic blue LEDs as well as combined red, blue or/and green LEDs light spectrum were superior to fluorescent lamp spectrum in micro-propagation of potato plantlets. Therefore, the application of RBG was suitable;BB and RB could be used as alternatives.

Transcriptome analysis reveals effects of red and blue lightemitting diodes(LEDs)on the growth,chlorophyll fluorescence and endogenous plant hormones of potato(Solanum tuberosum L.)plantlets cultured in vitro

Red and blue light illumination has been reported to significantly affect plantlet growth.Potato is an important food and feed crop in the world and potato plantlet cultured in vitro plays an important role in potato production.However,few studies have documented the effects of red and blue light on the growth of potato plantlets revealed at the transcriptome level.The objective of this study was to determine the growth and physiological responses of potato plantlets cultured in vitro under monochromatic red(RR),monochromatic blue(BB)as well as combined red and blue(RB)LEDs using the RNA-Seq technique.In total,3150 and 814 differentially expressed genes(DEGs)were detected in potato plantlets under RR and BB,respectively,compared to RB(used as control).Compared to the control,the DEGs enriched in"photosynthesis"and"photosynthesis-antenna proteins"metabolic pathways were up-regulated and down-regulated by BB and RR,respectively,which might be responsible for the increases and decreases of maximum quantum yield(F_(v)/F_(m)),photochemical quantum yield(φ_(PSII)),photochemical quenching(q_(P))and electron transfer rate(ETR)in BB and RR,respectively.Potato plantlets exhibited dwarfed stems and extended leaves under BB,whereas elongated stems and small leaves were induced under RR.These dramatically altered plantlet phenotypes were associated with variable levels of endogenous plant hormones gibberellin(GAs),indoleacetic acid(IAA)and cytokinins(CKs),as assessed in stems and leaves of potato plantlets.In addition,monochromatic red and blue LEDs trigged the opposite expression profiles of DEGs identified in the"plant hormone signal transduction"metabolic pathway,which were closely related to the endogenous plant hormone levels in potato plantlets.Our results provide insights into the responses of potato plantlets cultured in vitro to red and blue LEDs at the transcriptomic level and may contribute to improvements in the micro-propagation of potato plantlets cultured in vitro from the light spectrum aspect.

节能减排政策工具降低碳强度影响机制研究——基于30省(市、自治区)数据的模糊集定性比较分析

采用模糊集定性比较分析法(fs QCA),以2012—2017年30个省(市、自治区)数据为样本,探究规制型、经济型和社会型节能减排政策工具中的六种细分工具,即规范性政策文本、产业结构调整、财政支出、碳排放权交易、节能减排专利和社会组织参与,对于降低碳强度的影响机制。研究发现:单个前因条件均不构成碳强度降低的必要条件。在所确定的有效组态中,规制型工具在东部和中西部地区均发挥主导且基础性作用,在东部地区的作用尤为明显;多元政策工具组合日渐成为中西部地区节能减排目标得以实现的强有力保障;社会型工具则更多依托于规制型和经济型工具作为辅助条件出现。不同政策工具对碳减排效果存在差异,进而针对不同地区提出科学合理的政策工具建议。