As the spreading of abandoned bamboo forests is becoming a serious problem in Japan, new possible uses for bamboo biomass are being sought toward controlling their further spread. In the present study, we investigated the potential of bamboo powder substrates in cultivation of horticultural plants as well as for bamboo powder to be used as a soil supplement in potting substrate recycling. Twenty varieties of ornamental flowering species were sown either in a conventional potting substrate or bamboo powder substrates. After 30 days, the cumulative germination rate of each variety was not affected by the type of substrate the plants were grown in. Although the overall plant growth of pot French marigold, pansy, and strawberry showed a tendency of being inferior in the bamboo powder substrates compared with the conventional potting substrate, it was improved by the addition of compost. The growth of French marigold also improved when the fermented bamboo powder substrate was additionally fertilized. We found that the microbiota present in the recycled potting substrate containing fermented bamboo powder was similar to that found in fresh potting substrate. These results indicate that bamboo substrate has great potential to be employed both as a growing substrate for various garden plants and as a soil supplement in recycling of used potting substrate.

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Blue flower color of Nemophila menziesii Hook. and Arn. is derived from a metalloanthocyanin, nemophilin, which comprises petunidin-3-O-[6-O-(trans-p-coumaroyl)-β-glucoside]-5-O-[6-O-(malonyl)-β-glucoside], apigenin-7-O-β-glucoside-4′-O-(6-O-malonyl)-β-glucoside, and Mg²⁺ and Fe³⁺ ions. The flavonoid biosynthetic pathway of nemophilin has not yet been characterized. RNA-Seq analysis of the petals yielded 61,491 contigs. These were searched using BLAST against petunia or torenia flavonoid biosynthetic proteins, which identified 11 putative full-length protein sequences belonging to the flavonoid biosynthetic pathway. RT-PCR using primers designed on the basis of these sequences yielded 14 sequences. Spatio-temporal transcriptome analysis indicated that genes involved in the early part of the pathway are strongly expressed during early-petal development and that those in the late part at late-flower opening stages, but they are rarely expressed in leaves. Flavanone 3-hydroxylase and flavonoid 3′,5′-hydroxylase cDNAs were successfully expressed in yeast to confirm their activities. Recombinant anthocyanin O-methyltransferase cDNA (NmAMT6) produced using Escherichia coli was subjected to biochemical characterization. Km of NmAMT6 toward delphinidin 3-O-glucoside was 22 µM, which is comparable with Km values of anthocyanin O-methyltransferases from other plants. With delphinidin 3-O-glucoside as substrate, NmAMT6 almost exclusively yielded petunidin 3-O-glucoside rather than malvidin 3-O-glucoside. This specificity is consistent with the anthocyanin composition of Nemophila petals.

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2 種類の主要アントシアニン（色素 1 と 2）が青色花弁のネモフィラ（Nemophila menziesii ‘Insignis blue’）およびその変異系統の紫色花弁から検出された．これら 2 種類のアントシアニンを青色花弁から単離し，化学およびスペクトル分析による構造解析を行った結果，ペチュニジン 3-O-［6-O-（シス-p- クマロイル）-β- グルコピラノシド］-5-O-［6-O-（マロニル）-β- グルコピラノシド］（色素 1）とペチュニジン 3-O-［6-O-（トランス-p- クマロイル）-β- グルコピラノシド］-5-O-［6-O-（マロニル）-β- グルコピラノシド］（色素 2）であり，色素 1 は新規化合物であった．さらに，2 種類の主要フラボノール配糖体（色素 3 と 5）と 2 種類の主要フラボン配糖体（色素 4 と 6）も青色花弁から単離され，ケンフェロール 3-（6- ラムノシル）- グルコシド-7- グルコシド（色素 3），アピゲニン 7,4′- ジグルコシド（色素 4），ケンフェロール3-（2,6- ジラムノシル）- グルコシド（色素 5），そしてアピゲニン 7- グルコシド-4′-（6- マロニル）- グルコシド（色素 6）と同定された．これら 4 種類のフラボノイドの内，色素 4 と 6 は紫色花弁からは検出されなかったことから，これらの違いにより花色が異なることが示唆された．

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