• Korean Journal of Plant Tissue Culture
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• v.27 no.4
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• pp.299-307
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• 2000

A large amount of information is currently available for somatic embryogenesis of plants. However, one common problem related to somatic embryos is that the conversion rate can be low for some species. Apical meristems are responsible for post-embryonic growth of the embryo. The low percentage observed is most likely a result of poor apical meristem development or defects in the meristem organization during somatic embryogenesis. In flowering plants, apical meristems are well developed by the late heart stage of zygotic embryo development. In conifers, such as white spruce, apical meristems are formed at the pre-cotyledon stage. Thus, apical meristem development occurs very early, prior to the maturation stage of embryo development. Once formed, meristems are stably determined. In the somatic embryo, as exemplified by white spruce, since embryo development is not synchronous, tissue differentiation including apical meristem formation occurs throughout the“maturation”stage. Different apical meristem organizations can be found among different individuals within a population. In contrast to their zygotic counterparts, the apical meristems appear not to be stably determined as their organization, as the shoot apical meristem especially, can be easily modified or disrupted. Precocious germination seldom results in functional plantlets. All these observations suggest that the conditions for somatic embryo maturation have not been optimized or are not suitable for meristem formation and development. The following strategies could improve meristem development and hence conversion: 1. Simulate in ouuio conditions to promote meristem development prior to the“maturation”treatment.2. Prevent deterioration of apical meristem organization during somatic embryo maturation.3. Promote further meristem development during embryo germination.

• Journal of Plant Biology
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• v.38 no.3
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• pp.281-288
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• 1995

The progressive differentiation of interfascicular cambium from residual meristem in the first internode of Ginkgo biloba seedlings was elucidated by light and electron microscopy. The cells of residual meristem were small and homogeneous and heterogeneous in their arrangement but those of the adjacent cortex and pith were large and homogeneous. Some interprocambial residual meristem progressively became elongated and vacuolated during the process of the differentiation. In tangential section, residual meristem composed of long and short cells. The eventual interfascicular cambium had long fusiform initials and short ray initials. Storage materials in the cells progressively disappeared from the interprocambial residual meristem and were absent in early interfascicular cambium. Both the radial and tangential walls of cells of the interprocambial residual meristem were almost the same, but the radial wall became progressively thicker than the tangential wall during differentiation of interfascicular cambium. From these results, it is clear that interfascicular cambium is gradually differentiated from residual meristem.

• Journal of Plant Biotechnology
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• v.6 no.4
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• pp.221-227
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• 2004

Protocol was established for production of virus free healthy seeds using meristem ($0.3-0.5\;\cal{mm}$ in size) culture and field management under net house condition in tomato. The isolated meristem was found well established in MS liquid medium containing $0.1\;\cal{mg}\;1^{-1}\;of\;GA_3$. For shoot and root development either from primary meristem or from nodal segment of meristem derived plants, semisolid MS medium having $0.5\;\cal{mg}\;1^{-1}$ of IBA was found most effective. The elimination of the studied viruses (ToMV, CMV, ToLCV) in meristem-derived plants was confirmed by DAS-ELISA test. For field management of the virus eradicated meristem-derived plants, use of net house was found very effective measures to check viral vector visit and eventually infection. The meristem-derived plants were vigor and high yielder than the native seed derived plants and produced healthy seeds. Due to stop vector visit, no viral symptoms were observed in both $R_1\;and\;R_2$ plants cultivated in net house condition. Starting of viral infestation was observed in $R_2$ generation when they were planted in open house condition without control of vector visit. Therefore, for management of viral diseases, use of virus free meristem derived plantlets and their subsequent cultivation in soil under net house condition without using any vector killing insecticide can be recommended for producing healthy seeds in tomato. The developed protocol for environmentally healthy tomato seed production in Bangladesh may be used in the countries having similar tropical like environment conducive for viral vector visit.

• Plant Resources
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• v.7 no.3
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• pp.200-205
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• 2004

Sweet potato infected with a viral disease (SPFMV) showed irregular chlorotic patterns, so called feathering associated with faint or distinct ring spots that have purple-pigmented borders. SPFMV was eliminated from sweet potato plants using meristem tip culture. MS medium supplemented with BAP (2mg/L) and NAA (0.05 mg/L) was used for shoot proliferation and 1/2 MS medium for rooting of the plants. Highest percentage of regenerated plants (60%) was obtained from the optimum size (0.3-0.5mm) meristem tips. Of these, 60% plants were found negative for SPFMV by RT-PCR. Virus detection by RT-PCR was found to be a reliable method. Meristem-tip culture to produce SPFMV-free quality sweet potato and virus detection by RT-PCR is an efficient, time saving and reliable method for production of SPFMV-free tissue culture raised plants.

• Journal of Plant Biology
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• v.35 no.3
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• pp.273-281
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• 1992

The origin of the interfascicular cambium from residual meristem can be elucidated by tangential and transverse observation. It is clear that there is structural distinction between interprocambial and interfascicular residual meristem and adjacent parenchyma in both the transverse and tangential view. Consequently, the residual meristem does not convert into parenchyma but, rather, becomes interfascicular cambium. In tangential view, the homogeneous structure of interfascicular residual meristem at an early stage changes gradually into a heterogeneous one at a later stage, with long and short cells from which fusiform and ray initials originate respectively. However, the homogeneous structure of parenchyma adjacent interfascicular residual meristem does not change into a heterogeneous one but remains the same at all stages of development. Therefore, the interfascicular cambium has a direct ontogenetic continuity with the residual meristem, and does not have its secondary origin from differentiated parenchyma. Furthermore, the ontogenetic pattern of the interfascicular cambium is almost the same as that of fascicular cambium.ambium.

• Molecules and Cells
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• v.19 no.3
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• pp.342-349
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• 2005

Cytokinins are adenine derivatives that regulate numerous plant growth and developmental processes, including apical and floral meristem development, stem growth, leaf senescence, apical dominance, and stress tolerance. However, not much is known about how cytokinin biosynthesis and metabolism is regulated. We identified a novel Arabidopsis gene, ALL, encoding an aldolase-like enzyme that regulates cytokinin signaling. An Arabidopsis mutant, all-1D, in which ALL is activated by the nearby insertion of the 35S enhancer, exhibited extreme dwarfism with rolled, dark-green leaves and reduced apical dominance, symptomatic of cytokinin-overproducing mutants. Consistent with this, ARR4 and ARR5, two representative primary cytokinin-responsive genes, were significantly induced in all-1D. Whereas SHOOT MERISTEMLESS (STM) and KNAT1, which regulate meristem development, were also greatly induced, expression of REV and PHV that regulate lateral organ polarity was inhibited. ALL encodes an aldolase-like enzyme that belongs to the HpcH/HpaI aldolase family in prokaryotes and is down-regulated by exogenous cytokinin, possibly through a negative feedback pathway. We propose that ALL is involved in cytokinin biosynthesis or metabolism and acts as a positive regulator of cytokinin signaling during shoot apical meristem development and determination of lateral organ polarity.

• Korean Journal of Plant Resources
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• v.23 no.3
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• pp.233-241
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• 2010

In vitro elimination of Sweet potato leaf curl virus (SPLCV) from infected sweet potato is difficult due to low number of virus-free plants obtained from meristem tip culture and long growth period required for the virus detection. In this study, efficient production of the SPLCV-free sweet potato by in vitro therapy coupled with a PCR assay for virus detection was investigated. Infected shoots cultured on Murashige and Skoog medium were treated at three different temperatures for 7 weeks followed by meristem tip culture on the medium with or without ribavirin at 50 mg/L. The regenerated plantlets were tested for virus infection by a PCR assay. The results showed that the both heat- and cold-treatments, and addition of the ribavirin did not have significant effect on efficiency of the virus elimination. The meristem size, however, greatly affected the survival rate. Meristems sized over 0.4 mm survived better than smaller ones (0.2-0.3 mm). The PCR assay was approved to be a rapid, sensitive and reliable for the SPLCV detection in regenerated plantlets. Therefore, combination of cultivating meristem tips sized 0.4-0.5 mm on the medium at $22^{\circ}C$ without ribavirin and detection of SPLCV in the regenerated plantlets by the PCR assay was an efficient system for the SPLCV elimination from infected sweet potato.

• Korean Journal of Plant Resources
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• v.17 no.3
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• pp.331-338
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• 2004

This study was conducted to obtain the virus free plants through meristem culture of carnation (Dianthus caryophillus). Four cultivars (Roland, Desio, Casha, Giant Gipsy) were collected for materials. The apical meristem 0.3-0.5mm in size was cultured on MS medium containing 3% sucrose, 0.9% agar at pH 5.8 with various plant growth regulators for 7 weeks. Among the cultivars, Giant Gipsy had a better response than other cultivars in shoot formation and reduced vitrification. Callus induction and shoot formation from the meristem culture were influenced by the various kinds of cytokine. Kinetin supplement was the most effective for shoot formation and NAA addition was good for callus induction among the treatments. Total 115 plantlets derived from apical meristem culture were checked for CarMV and CarRSV infection by ELISA test. Among them, 40 plantlets (34.8%) were infected with CarMV but not detected for CarRSV.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.4
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• pp.344-349
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• 1981

This study was conducted to define the effect of 2.4-D, NAA, Benzyladenine, and basic mediums on the callus induction and the organ differentiation from the meristem tips and the stem and leaf segments of the potato. Benzyladenine promoted the induction and growth of shoot from the meristem tip of potato but inhibited initiation of roots and induction of callus. At higher concentration of NAA than 0.5 ppm and of 2.4-D than 1.0 ppm the shoots were not initiated but the callus was induced from the meristem. The callus growth was significantly promoted on the medium containing NAA than 2.4-0. The initiation and growth of the shoots from the potato meristem was significantly increased in the medium containing 2.4-D and BA, or NAA and BA, compared with those containing BA, NAA or 2.4-D alone. The callus was more easily induced from the stem segments than the leaf segments of potato. And the 2.4-D was more effective for the induction and growth of the callus than the NAA. MS medium diluted its concentration to 1/2 was more suitable for the initiation and growth of the shoots from the potato meristem than the MS standard medium. For the initiation and growth of the shoots from the potato meristem, the most desirable medium was the diluted MS medium containing 1.0 ppm BA and 0.1 ppm NAA or 0.1 ppm 2.4-D.

• Korean Journal of Medicinal Crop Science
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• v.5 no.3
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• pp.186-190
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• 1997

This study was carried out to investigate the effect of polyamines, salt strength. sucrose and gelling agents on the regeneration of plantlets by meristem culture of Aloe arborescens Mill. and Aloe vera L.. Shoot multiplication was more effective when 10mg/ l spermine in Aloe arborescens and 1mg/ l spermidine in Aloe vera added into MS medium than when other polyamines were treated into media. A quarter strength of MS medium was effective for rooting of shoots regenerated. Higher concentration of sucrose (45g/ l) was more effective for shoot regeneration. Addition of 4g/ l gelrite into the medium was effective for induction of multiple shoots from Aloe than that of agar or other concentrations of gelrite. When plantlets regenerated from meristem culture were transferred to pot. survival rate of plantlets was 80% on perlite and was 95% on vermiculite. respectively.