コロナウィルスの大規模流行により，図書館や博物館などの公共空間においても人が一定の間隔を保つ”ソーシャルディスタンシング”を維持することが求められている．”ソーシャルディスタンシング”は感染防止の観点から必要な措置であるが，その一方で，施設内の椅子や利用スペースに利用禁止を促す表示が溢れ，人々を広く受け入れることが役割である公共空間に相応しくない状況が拡がりつつあることも事実である．発表者らは，学芸員や研究者などの学術関係者とデザイナーが連携して，コロナ禍における公共空間における文化活動の再生を目指す「キテンプロジェクト」を実施している．本発表では，「キテンプロジェクト」を紹介するとともに，コロナ禍における公共空間と学術関係者・デザイナーとの関わりについて報告する．

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活着期, すなわち植え付けから約3カ月後までのキャッサバに対する, 乾燥の時期および期間の及ぼす影響を, とくに根系発達に注目して検討した. 植え付け後9～44日に乾燥処理を与えた場合(前期乾燥処理), 44～82日に同処理を与えた場合(後期乾燥処理), いずれも土壌を湿潤に保った対照区と比べて葉数, 地上部乾物重が有意に減少した. また, 植え付け後9～82日目まで乾燥処理を与えた区(全期乾燥処理)では, 後期乾燥処理区と類似の地上部生長の減少傾向が認められた. 根系発達についてみると, 前期乾燥処理区では, 不定根数・長, 第1次・2次・3次側根数, 乾物重が減少した. しかし再灌水後, これらの値は増加する傾向を示した. 一方, 後期乾燥処理区では, 同様に不定根数・長, 第1次・第2次側根数は乾燥によって減少したが, 第3次側根数は促進される傾向を認めた. また, 不定根が太くなることによって, 根系乾物重も増加した. 全体として, これらの結果はキャッサバ活着期においては乾燥に対して感受性が高いことを示している.

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Anthropogenically increased nitrogen (N) deposition may affect the nutrient dynamics of forested ecosystems. To investigate the potential effects of excessive N deposition on Japanese forests, we treated the soil in a 20-year-old Japanese cedar (Cryptomeria japonica) stand with 10 l m^-2 of 10 mM HNO₃ solution, 10 mM NH₄NO₃ solution, or tap water (as a control), monthly for 7 years. A total of 168 and 336 kg N ha^-1 year^-1 was added in the HNO₃ and NH₄NO₃ plots, respectively. Tree growth, the amount of nutrients and the carbon concentration of both current shoots and fine roots (<2 mm in diameter) in the surface soil (0-5 cm) were measured. The foliar N concentration increased in both N-fertilized plots during the first 3 years, particularly in the NH₄NO₃ plots. Similarly, the fine- N concentration was greater in the N-fertilized plots than in the control plots. However, growth in both height and diameter at breast height of Japanese cedar trees were not significantly affected by N fertilization. The foliar K and P concentrations tended to decrease in treatment plots over time when compared with the control plots. Our study suggests that 7 years of excessive N fertilization had no positive or negative effect on the growth of young Japanese cedar trees, although the nutrient status of current shoots and fine roots was altered.

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The importance of fine roots in forest ecosystem processes is well known. However, the contribution of understory vegetation to underground ecosystem processes is not well understood. We tested the hypothesis that fine- biomass (FRB) and performance of the overstory and understory independently decrease with increasing soil N availability in cool-temperate deciduous broad-leaved natural forests and larch plantations in Japan. The mean contribution of understory FRB to total FRB (tree + understory) ranged from 4% to 78% (mean 37%). Tree FRB was negatively correlated with understory FRB, and understory FRB was dominant to tree FRB in infertile soil. Understory and total FRB were negatively correlated with soil net N mineralization rate, whereas tree FRB showed a quadratic relationship with soil N mineralization rate with the peak observed at mineralization of 58.4 kg N ha^-1 y^-1. The low tree FRB at infertile sites may be due to a belowground competitive effect of understory fine roots on tree FRB. Understory fine- nitrogen concentration (FRN) and leaf to fine- (L/FR) ratio were positively correlated with N mineralization rate. However, tree L/FR was not significantly correlated, whereas tree FRN was positively correlated, with soil N mineralization rate, suggesting that the leaf production efficiency of trees might not increase even on infertile soil. We suggest that belowground processes of overstory trees might change depending on understory vegetation, and that understory vegetation might affect the fine roots of overstory trees, which did not increase mass allocation but increased N use efficiency under low FRN.

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Fine roots of Cryptomeria japonica were separated into two functional groups: primary roots that serve as the principal agent for water and nutrient absorption and secondary roots that have transport capacity and protect the plant from environmental stress. Individual roots can also be categorized by three characteristics: diameter, branching order, and number of protoxylem groups. We investigated the relationships of these two functional groups with the three categories and evaluated which category was a better index for distinguishing primary from secondary roots by using the Pianka overlap index. Primary and secondary roots showed no exact correspondence to any of the three categories and had overlap in each category. Therefore neither was a useful indicator to distinguish primary from secondary roots. However, in the case of Cryptomeria japonica, we can roughly distinguish primary from secondary roots on the basis of whether diameter is less than or greater than 0.6 mm.

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Mt. Hayachine in Iwate prefecture is characterized by serpentine site, which is known to have high concentrations of Ni. In general, few plants that can tolerate high concentrations of Ni can grow in serpentine soil. Thujopsis dolabrata var. hondai occurs naturally on Mt. Hayachine. In this study, we hypothesized that T. dolabrata var. hondai shows Ni tolerance due to detoxification by phenolics. We collected T. dolabrata var. hondai seedlings and -zone soil from the Kadoma National Forest on Mt. Hayachine to analyze the concentrations of Ni, other heavy metals, and macronutrients. The seedling roots had high concentrations of Ni. Further, we conducted a pot experiment by using 1-month-old sterile seedlings grown in three types of sterilized soils-Kadoma soil (obtained from the Kadoma National Forest), Tsugaru forest soil, and nursery soil-and compared the concentrations of Ni, nutrients, and catechin, as well as the growth of seedlings in the different soils. The pot experiment indicated that the roots of seedlings grown in Kadoma forest soil contained high concentrations of Ni and catechin, which could act as an antioxidant and a possible Ni-chelating compound that detoxified Ni in the plant cells. We concluded that T. dolabrata var. hondai seedlings growing in the serpentine site of Mt. Hayachine accumulated Ni and could detoxify it by producing high concentrations of catechin.

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To analyze the function of SYNC1, an Arabidopsis asparaginyl-tRNA synthetase gene, the FOX-hunting system using super-growing roots (SR) from the legume species Lotus corniculatus was employed. One transformed line, FSL#121, was compared to parental SR and to an SR line harboring the empty vector (Control), all of which were grown in vivo using vermiculite pots. The level of several free amino acids was higher in FSL#121 than SR. Concomitantly, FSL#121 had a distinct phenotype of greater shoot length, stem diameter and shoot fresh weight compared with SR. Also, the length, diameter and fresh weight were greater in FSL#121 than SR. Furthermore, the greater number of nodules in FSL#121 increased the nitrogen fixation activity per whole plant. Therefore, SYNC1 overexpression caused distinct changes in plant growth, increased the number of nodules, and may be involved in increasing the amount of free amino acids, especially asparagine.

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With the advent of the molecular era of plant biology, the location and activity of the quiescent centre (QC) within the meristem were reappraised with respect to the transport and distribution of hormones, especially auxin. Later, when methods for probing gene activity became established, the genes and their regulators that were identifiably specific to the QC were also actively studied, at first in relation to the establishment of the and its QC in the proembryo and later in relation to the interaction of the QC with neighbouring meristem cells. Auxin distribution in and around the QC was found to be associated with co-located oxidative enzymes which established a redox system within the apex. This system is pivotal in both maintenance of quiescence and the activation of cell proliferation in the QC via the generation of reactive oxygen species (ROS) and their interaction with mitochondria. These and other features of QC biology are summarised.

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Within the tip of roots meristems of angiosperms and gymnosperms there is a small group of cells known as the quiescent centre (QC). The concept of the QC was developed 60 years ago by FAL Clowes, working in the Botany School, Oxford University, UK. To celebrate the Jubilee of the QC, a brief outline of the work that led to its demonstration by autoradiography was presented by Dubrovsky and Barlow (2015). The present article traces Clowes’s subsequent experimental studies of the QC, especially with regard to how X-irradiation became an important tool for elucidating the properties and significance of the QC for development. Also reviewed are some of the consequences that subsequently arose from this work with radiation, in particular the concerns over the use of radioisotopes in attempts to describe the kinetics of cell proliferation in the meristem.

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Understanding morphology of lateral roots in rice is important in modeling different agricultural management system. The objective of the study was to explore the morphology of lateral roots of lowland transplanted-aman rice cultivars to mechanistically model length, surface area and volume of an individual . Seedlings of twelve selected rice cultivars at 30 days of age were transplanted and a series of measurements was carried out on 14, 20, 33 and 60 days after transplantation (DAT). Lateral roots and hairs were studied under a light microscope. Individual main axes produced up to second-order laterals. Mean main axis diameter and length of twelve cultivars measured 0.94 mm and 20.4 cm respectively at 60 days after transplantation. Diameter reduced at the first-order and second-order laterals up to 4.56 and 21.4 times respectively compared to main axis on 60 DAT. hair diameter measured 4.0 μm. An individual on 60 DAT estimated 911 m in the length, 1714 cm² in the surface area and in the 467 mm³ volume. hairs had the highest contribution towards total length and surface area of an individual whereas main axis and first order laterals mostly contributed volume.

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Phosphorus (P) is patchily distributed in soil because of its slow diffusion, especially in soil with a high phosphate absorption coefficient (PAC). responses to localized supply of phosphate were studied in Sesbania cannabina grown in volcanic andosol, which has a high PAC. Seedlings were grown in soil that was supplied with 0, 10, 100, 500, or 1000 mg P kg^-1. After 30 days, analyses of plant P and morphological were conducted. Further rhizobox experiments were also conducted. Seedlings were grown with layered P sources or localized P patches. Densely branched lateral roots (DBLRs) developed only in the 10 and 100 mg P kg^-1 treatments. Although an increase in shoot dry weight (DW) was observed in the 500 and 1000 mg P kg^-1 treatments, DBLRs were not observed. The number of DBLRs was positively correlated with shoot DW, DW, and number of nodules, and negatively correlated with phosphorus use efficiency of shoots and roots. The rhizobox experiment showed that most DBLRs were observed in the layer with added P and in the position where P fertilizer was present. DBLRs developed so as to monopolize the P fertilizer by completely enveloping the area around it. The results suggest that DBLR formation is one of S. cannabina’s P acquisition strategies.

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Two Melaleuca species, M. cajuputi and M. bracteata, were compared to identify the factors determining their distinct aluminum (Al) resistance levels. The presence of Al in a liquid culture medium (maximum tested concentration, 2 mM) did not affect the growth of M. cajuputi, but severely inhibited the growth of M. bracteata. The Al content in the roots was 50% higher in Al-sensitive M. bracteata than in Al-resistant M. cajuputi. Al penetration and tissue damage were obvious in the roots of M. bracteata, but only mild in the roots of M. cajuputi. Relatively high levels of fumarate were released by the roots of M. cajuputi, but not by those of M. bracteata. Supplementation of Al-containing liquid media with fumarate resulted in a reduction of Al toxicity on M. bracteata. These results suggest that Al-resistant M. cajuputi releases fumarate from its roots, thereby detoxifying Al.

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For systematic functional analysis of genes, we attempted the application of the FOX-hunting system to super growing-roots (SR) of legume species Lotus corniculatus which was previously reported by Himuro et al. (2011). In this study, we investigated the functional analysis of FSL#35, which was expressed by the rolB gene derived from the Agrobacterium rhizogenes Ri plasmid. In monoculture roots grown in liquid media, the FSL#35 showed specific phenotypes that increased length, lateral number and surface area compared with SR. These enhanced phenotypes of FSL#35 were caused by cell profile alteration, while increased total length and increased lateral number were caused by the expansion of cortex cells and increased pericycle cells, respectively. In addition, the FSL#35 showed high and specific respiration activity compared with SR. These results suggest that distinct cell profiles of FSL#35 were induced by the alteration of respiration activity in tissue. The enhanced growth in the FSL#35 might be induced by alteration of ROS metabolisms. Investigating the details of the rolB gene function, for example by phytohormone analysis, will elucidate the novel benefits of the rolB gene for agriculture.

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Plants including tomato produce several kinds of chelator proteins such as metallothioneins (MTs) for protection against Hg²⁺ toxicity. However, the mechanism of protection from Hg²⁺ is not perfectly clear. Hg²⁺ content subsequently was plateaued from days 1 to 7. Cell death and DNA digestion were not observed in the primary in the presence of Hg²⁺ over the 7 days. The predicted protein sequences of 5 tomato type 2 MT-like (MT2-like) proteins were compared. The coding sequences of accession number Z68185 had no Cys-Cys motif in the N-terminal. However, the Z68185 cDNA genetic recombinant showed high resistance to Hg²⁺ in bacteria. In tomato, the expression was observed in the roots, but not in the leaves or stems. mRNA of the MT2-like protein was measured in tomato seedlings exposed to 1 μM Hg²⁺. The expression level did not increase until day 3, but increased expression was observed after day 5. These results suggest that new Metallothionein2-like protein express in specific and it may trap mercury. Our results indicate that functional identification of an MT2-like protein will be useful for molecular breeding designed to improve plant tolerance to Hg²⁺.

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Water stress is a major limiting factor for plant growth and development. In this study, we investigated the effects of L-β-phenyllactic acid (LPA) on growth of rice (Oryza sativa L.) seedlings under polyethylene glycol (PEG)-induced water deficit conditions. Seedlings were culture at 30 °C for 14 days in growth pouches supplemented with 1/100-strength Murashige and Skoog (MS) medium and PEG in the presence or absence of 100 mg L^-1 LPA. As evidenced by plant height, LPA application enhanced seedling growth under PEG-induced water deficit by 13%. The shoot dry weight was slightly increased, whereas that of roots was markedly enhanced during LPA treatment by 26% under water-deficit conditions. No difference was observed among treatments in the number of roots per seedling. The ratio of shoot dry weight to shoot length (RWL) was constant regardless of treatment, indicating that LPA does not cause spindly shoot growth. The total length, surface area, and volume of fine roots were increased by LPA under PEG-induced water deficit conditions. Plant height was significantly correlated with total surface area and volume. The results imply that PEG-induced water deficit in rice seedlings can be alleviated by LPA application. This alleviative effect is partially attributable to alterations in system developmental patterns, with increases in fine total length, surface, and volume accelerating water and nutrient acquisition from the culture medium.

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Soil sickness is a widespread problem in replanted apple orchards with a complex symptomatology and etiology influenced by soil and climate conditions. Consequently, a conclusive technical solution is still lacking for intensive apple orchards. The present work aims to analyze the morphological and functional changes occurring in the M9 apple systems growing in pot filled with soil derived from five different European growing areas. For each growing area, the soil was collected from the apple orchard and used directly in the pot or gamma-ray sterilized before potting. Soil from a neighborhood fallow was also used as control for each growing area. In the non-sterilized replant soils plants developed poor systems due to a limited biomass allocation. Fibrous roots production was particularly compromised. The roots had a smaller diameter and a lower ramification index. The cell membrane integrity was also lower. Gamma-ray sterilized replant soils increased growth, branching and cell integrity, while nearby fallow soil induced an intermediate behavior. The magnitude of the symptoms showed a significant interaction between soil treatment and sampling site and growth was correlated with the organic matter content in the soils.

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