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.

Effects of Lanthanum and Europium on Rooting of Plantlet Eriobotrya Japonica Lindl. in vitro

The effect of La 3+ and Eu 3+ on the rooting of Eriobotrya japonica Lindl. plantlet in vitro was studied with adding La 3+ and Eu 3+ to the rooted medium. The rooting rate, the number of root and the length of root were studied after transplanting 20 d. The activity of peroxidase, nitrate reductase and fresh weight of roots were determined after transplanting 44 d. The results show that the optimum concentration range of La 3+ (1.0～3.0 μmol·L -1), Eu 3+ (2.0～3.0 μmol·L -1) in the rooted medium can increase the rooting rate and the fresh weight of roots, and promote the length of root and raise the activities of peroxidase and nitrate reductase significantly. La 3+ has more effect in improving the rooting rate, root length and the activities of peroxidase and less effect in promoting root fresh weight and the activities of nitrate reductase than Eu 3+.

A rapid multiplication system for'Candidatus Liberibacter asiaticus'through regeneration of axillary buds in vitro

‘Candidatus Liberibacter asiaticus(CLas)’,which causes citrus Huanglongbing(HLB)disease,has not been successfully cultured in vitro to date.Here,a rapid multiplication system for CLas was established through in vitro regeneration of axillary buds from CLas-infected‘Changyecheng’sweet orange(Citrus sinensis Osbeck).Stem segments with a single axillary bud were cultured in vitro to allow CLas to multiply in the regenerating axillary buds.A high CLas titer was detected in the regenerated shoots on an optimized medium at 30 days after germination(DAG).This titer was 28.2-fold higher than in the midribs from CLas-infected trees growing in the greenhouse.To minimize contamination during in vitro regeneration,CLas-infected axillary buds were micrografted onto seedlings of‘Changyecheng’sweet orange and cultured in a liquid medium.In this culture,the titers of CLas in regenerated shoots rapidly increased from 7.5×10^(4)to 1.4×10^(8)cellsμg^(-1)of citrus DNA during the first 40 DAG.The percentages of shoots with>1×10^(8)CLas cellsμg^(-1)DNA were 30 and 40%at 30 and 40 DAG,respectively.Direct tissue blot immunoassay(DTBIA)indicated that the distribution of CLas was much more uniform in regenerated plantlets than in CLas-infected trees growing in the greenhouse.The disease symptoms in the plantlets were die-back,stunted growth,leaf necrosis/yellowing,and defoliation.The death rate of the plantlets was 82.0%at 60 DAG.Our results show that CLas can effectively multiply in citrus plantlests in vitro.This method will be useful for studying plant-HLB interactions and for rapid screening of therapeutic compounds against CLas in citrus.

Effects of Neodymium on Nitrogen Metabolism of Plantlet Loquat in Vitro

The effect of NdCl_3 on the rooting and nitrogen metabolism of loquat in vitro was studied when NdCl_3 was added to the rooted medium. The results show that 0.4 μmol·L^(-1) NdCl_3 in the rooted medium can obviously increase the rooting rate, length of root and fresh weight of roots, and enhance the activities of nitrate reductase, glutamine synthetase, glutamate dehydrogenase in the root system and in the leaves. The transformation of NO_3^- to NH_4^+ in root system and leaves are promoted and the nitrogen metabolism is accelerated with 0.4 μmol·L^(-1) NdCl_3 treatment.

Effects of Lanthanum on Root Growth and Senescence of GF_(43) (Prunus domestica) Plantlet in Vitro

The effect and the action mechanism of lanthanum on GF_(43) plantlet in vitro were studied. The results of experiments show that root growth rate and dry weight of GF_(43) by LaCl_3 treatments increase. The activities of antioxidant enzymes in root system such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) apparently enhance. Moreover ·O^-_2 and malond ialdehyde (MDA) contents and cell membrane permeability of GF_(43) are decreased by LaCl_3. The relatively stable membrane structure of cell could also be maintained and the root ageing of GF_(43) plantlet in vitro delays.

Effect of Lanthanum on Deferring Root Ageing of Peach Plantlet in Vitro

Poor adventitious root formation is a major obstacle in micropropagation and in conventional propagation. The effects of LaCl_3 on root growth and deferring the root ageing of peach plantlet in vitro were investigated. The results show that the optimum concentration of LaCl_3 (2.5 μmol·L -1) in the rooted medium can significantly increase the rooting rate, the root length and the fresh weight, promote the activities of superoxide dismutase (SOD); catalase (CAT) and peroxidase (POD) and decrease the production rate of O_2 ·-, the malondialdehyde (MDA) contents and the plasma membrane permeability. There are important theory meaning and practical value in applying LaCl_3 in the rooting medium to raise the rate of rooting and transplant for stone fruit tree.

Effects of red and blue LEDs on in vitro growth and microtuberization of potato single-node cuttings

The objectives of this study were to investigate the effects of red and blue LEDs on in vitro growth and microtuberization of potato(Solanum tuberosum) singlenode cuttings. Explants were incubated under 6 light treatments: 100% red LEDs(R), 75% red LEDs + 25%blue LEDs(3 RB), 50% red LEDs + 50% blue LEDs(RB),25% red LEDs + 75% blue LEDs(R3 B), 100% blue LEDs(B) and white LEDs(W). Most of the growth and physiological parameters were significantly higher in3 RB than W. Enhancement of leaf area and chlorophyll concentrations were obtained in B. Leaf stomata were elliptical with the lowest density in 3 RB. However, those in W were round in shape, and those with the smallest size and the highest density were observed in R. Most of the characteristics of microtuberization were also improved in3 RB. The combined spectra of red and blue LEDs increased the number of large microtubers. The fresh weight of individual microtubers in R and W were increased, but not their number. These results suggest that, of the treatments assessed, 3 RB is optimal for the in vitro growth of potato plantlets and the combination of red and blue LEDs is beneficial for microtuberization.