Effects of Rising Temperature on Growth, Yield and Dry-matter Production of Winter Wheat

Many studies on the crop response to climate change have been examined for isolated plnts or plants grown in a small-scale popuration. We constructed a Temperature Gradient Chamber(TGC) in a lowland field of Okayama University to clarify the effect of rising temperature on growth, yield and dry-matter production of winter wheat during the whole growth season. The four experimental plots were arranged by the distance from the intake side, TGI(control), TG2, TG3, and TG4. The temperature gradient occurred from TG1 to TG4, the daily ,mean temperature in TG4 increased 2.8℃ more than that of TG1. The dry weight in hight-temperature plots was larger than TG1. The grain yield per M2 was lowest in TG1(218g) and highest in TG2(248g), but gradually decreased with resing temperature in TG3(230g) and TG4(225g). The percentage og spikelet sterility and floret sterillity were not significantly different among the plots. The grain yield tended to decrease with higher the temperature more than 28℃ during the ripening period due to the decrease in dry-matter accumulation in the panicle at the latter ripening period. Clearly, rising temperature increased the wheat grain yield until 28℃ of daily mean temperature during the ripening period, furtuer rise in temperature limited the yild due to the decline in photosynthetic activity.温暖化による気温上昇を想定し，温度勾配チャンバー（TGC：Temperature Gradient Chamber）を用いて播種から収穫までの長期間の気温上昇処理が，コムギの生育収量，乾物生産におよぼす影響を検討した．TGC は，水田内に設置したものを使用し，換気ファンを常時稼動させることにより昼温のみ温度勾配を生じさせ，栽培試験を行った．コムギ品種イワイノダイチを供試し，開口部から閉口部に向かって対照区TG１，高温区TG２，TG３，TG４の４試験区を配置した．１週間毎の生育調査に加え，部位別乾物重の調査を栄養成長期，出穂期，登熟期，収穫期に行った．また，収穫期に収量と収量構成要素を調査した．TGC 内の気温は，開口部のTG１に比べて閉口部のTG４で平均気温で2.8℃，最高気温で5.8℃の気温上昇がみられた．草丈は，生育期間を通してTG１に比べTG２～TG４の高温区で伸長し，最終草丈はTG１（72.5㎝）＜TG２（74.9㎝）＜TG３（75.6㎝）＜TG４（79.9㎝）の順となった．茎数は，TG１に比べて，TG２では増加，TG３，TG４では減少する傾向がみられたが，有意性は認められなかった．全乾物重は高温区で増加する傾向がみられ，収穫期の全乾物重はTG１に比べてTG２，TG３，TG４でそれぞれ25.9 ，21.2 ，23.2 増加した．出穂後の個葉光合成速度は高温区で低下し，TG１に比べてTG４で出穂15日後には27.8 ，出穂30日後には63.6 と著しく低下した．子実収量は，TG１（218 gm-2）＜TG４（225 gm-2）＜TG３（230 gm-2）＜TG２（248 gm-2）の順となり，これには１穂粒数の増加，千粒重の低下が関係していた．１穂粒数は，高温区で１穂小花数が増加し，それに伴う稔実粒数の増加により多くなった．千粒重は，登熟中期から収穫期にかけての粒重がTG１，TG２では増加したものの，TG３，TG４では抑制傾向にあり，早期に登熟が完了したため高温区で小さくなっ た．TG２の子実収量は，１穂粒数の増加によるシンクの拡大に加えて，登熟後期まで粒重の増大が継続したため増収となった．TG３，TG４では，粒重が小さく，シンクの拡大を補償できなかったことが減収につながった．気温と子実収量の関係をみると，登熟期の平均気温が28℃を超えることで減収につながることがわかった．以上より，気温上昇は，コムギの生産性を概ね向上させるものの，子実収量に与える影響は稔実粒数の低下よりも，登熟中期以降の子実肥大が影響すると推察された

Radiative spacetimes approaching the Vaidya metric

We analyze a class of exact type II solutions of the Robinson-Trautman family which contain pure radiation and (possibly) a cosmological constant. It is shown that these spacetimes exist for any sufficiently smooth initial data, and that they approach the spherically symmetric Vaidya-(anti-)de Sitter metric. We also investigate extensions of the metric, and we demonstrate that their order of smoothness is in general only finite. Some applications of the results are outlined.Comment: 12 pages, 3 figure

Simulations of slow positron production using a low energy electron accelerator

Monte Carlo simulations of slow positron production via energetic electron interaction with a solid target have been performed. The aim of the simulations was to determine the expected slow positron beam intensity from a low energy, high current electron accelerator. By simulating (a) the fast positron production from a tantalum electron-positron converter and (b) the positron depth deposition profile in a tungsten moderator, the slow positron production probability per incident electron was estimated. Normalizing the calculated result to the measured slow positron yield at the present AIST LINAC the expected slow positron yield as a function of energy was determined. For an electron beam energy of 5 MeV (10 MeV) and current 240 $\mu$A (30 $\mu$A) production of a slow positron beam of intensity 5 $\times$ 10$^{6}$ s$^{-1}$ is predicted. The simulation also calculates the average energy deposited in the converter per electron, allowing an estimate of the beam heating at a given electron energy and current. For low energy, high-current operation the maximum obtainable positron beam intensity will be limited by this beam heating.Comment: 11 pages, 15 figures, submitted to Review of Scientific Instrument

Angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo1.73Fe0.27B2

We have performed angle-resolved photoemission spectroscopy of Co-based boride superconductor LaCo1.73Fe0.27B2 (Tc = 4.1 K), which is isostructural to the 122-type Fe-pnictide superconductor with the pnictogen atom being replaced with boron. We found that the Fermi level is located at a dip in the density of states (DOS) in contrast to Co-pnictide ferromagnets. This reduction in DOS together with the strong Co 3d-B 2p covalent bonding removes the ferromagnetic order and may cause the superconductivity. The energy bands near the Fermi level show higher three dimensionality and a weaker electron-correlation effect than those of Fe pnictides. The Fermi surface topology is considerably different from that of Fe pnictides, suggesting the difference in the superconducting mechanism between boride and pnictide superconductors.Comment: 5 pages, 4 figure

Unoccupied topological surface state in Bi2_{2}Te2_{2}Se

Bias voltage dependent scattering of the topological surface state is studied by scanning tunneling microscopy/spectroscopy for a clean surface of the topological insulator Bi$_2$Te$_2$Se. A strong warping of constant energy contours in the unoccupied part of the spectrum is found to lead to a spin-selective scattering. The topological surface state persists to higher energies in the unoccupied range far beyond the Dirac point, where it coexists with the bulk conduction band. This finding sheds light on the spin and charge dynamics over the wide energy range and opens a way to designing opto-spintronic devices.Comment: 5 pages, 4 figure

Surface Scattering via Bulk Continuum States in the 3D Topological Insulator Bi2_{2}Se3_{3}

We have performed scanning tunneling microscopy and differential tunneling conductance ($dI/dV$) mapping for the surface of the three dimensional topological insulator Bi$_{2}$Se$_{3}$. The fast Fourier transformation applied to the $dI/dV$ image shows an electron interference pattern near Dirac node despite the general belief that the backscattering is well suppressed in the bulk energy gap region. The comparison of the present experimental result with theoretical surface and bulk band structures shows that the electron interference occurs through the scattering between the surface states near the Dirac node and the bulk continuum states.Comment: 5 pages, 4 figure

Neural Induction in Xenopus: Requirement for Ectodermal and Endomesodermal Signals via Chordin, Noggin, β-Catenin, and Cerberus

The origin of the signals that induce the differentiation of the central nervous system (CNS) is a long-standing question in vertebrate embryology. Here we show that Xenopus neural induction starts earlier than previously thought, at the blastula stage, and requires the combined activity of two distinct signaling centers. One is the well-known Nieuwkoop center, located in dorsal-vegetal cells, which expresses Nodal-related endomesodermal inducers. The other is a blastula Chordin- and Noggin-expressing (BCNE) center located in dorsal animal cells that contains both prospective neuroectoderm and Spemann organizer precursor cells. Both centers are downstream of the early β-Catenin signal. Molecular analyses demonstrated that the BCNE center was distinct from the Nieuwkoop center, and that the Nieuwkoop center expressed the secreted protein Cerberus (Cer). We found that explanted blastula dorsal animal cap cells that have not yet contacted a mesodermal substratum can, when cultured in saline solution, express definitive neural markers and differentiate histologically into CNS tissue. Transplantation experiments showed that the BCNE region was required for brain formation, even though it lacked CNS-inducing activity when transplanted ventrally. Cell-lineage studies demonstrated that BCNE cells give rise to a large part of the brain and retina and, in more posterior regions of the embryo, to floor plate and notochord. Loss-of-function experiments with antisense morpholino oligos (MO) showed that the CNS that forms in mesoderm-less Xenopus embryos (generated by injection with Cerberus-Short [CerS] mRNA) required Chordin (Chd), Noggin (Nog), and their upstream regulator β-Catenin. When mesoderm involution was prevented in dorsal marginal-zone explants, the anterior neural tissue formed in ectoderm was derived from BCNE cells and had a complete requirement for Chd. By injecting Chd morpholino oligos (Chd-MO) into prospective neuroectoderm and Cerberus morpholino oligos (Cer-MO) into prospective endomesoderm at the 8-cell stage, we showed that both layers cooperate in CNS formation. The results suggest a model for neural induction in Xenopus in which an early blastula β-Catenin signal predisposes the prospective neuroectoderm to neural induction by endomesodermal signals emanating from Spemann's organizer

Effects of Rising Temperature on Grain Quality and Palatability of Rice Cultivars

The effects of high temperatures on grain quality and palatability of cooked rice of four rice cultivars were examined in a temperature gradient chamber (TGC). Experimental plots going from TG1 (near the air intake side) to TG3 (near the air exhaust side) along the temperature gradient in TGC, corresponding to low and high temperature, and an open field plot (outside of TGC) were arranged. The mean and maximum air-temperatures in TG3 were 3.6℃ and 7.2℃ higher, respectively, than those in TG1. Brown rice yield per m2 in the outside was the highest, and those in the TGC plots were lower than outside in all cultivars. This yield decline was due to the decrease in the percentage of ripened spikelets. The increase in the percentage of sterile spikelets due to high temperatures in Nikomaru and Akimasari was larger than that in Hinohikari and Akebono. The yield difference among TGC plots was not significant. High temperature increased the white berry grains and white back grains in Hinohikari and Akebono, respectively. The overall eating quality (＋3 to －3) in the outside was in the order of Nikomaru (0.56) ＞Akimasari (0.50)＞Hinohikari (0.00)＞Akebono (－0.06). The overall eating quality in TG3 was lower than outside, especially in the quality of appearance. However, the decreasing degrees of appearance quality in Nikomaru and Akimasari were smaller than those in Hinohikari and Akebono. The protein content of milled rice in TG3 (6.0−7.8%) was higher than that in the outside (8.6−10.4%) in all cultivars. The increase in protein content by higher temperature was in the order of Akebono (4.4%)＞Hinohikari (1.9%)＝Akimasari (1.9%)＝Nikomaru (0.8%). In terms of grain quality, the cultivation of new cultivars, Nikomaru and Akimasari are recommended when air temperature exceeds normal years. However, yield reductions in Nikomaru and Akimasari caused by high temperatures were larger than those in the conventional cultivars, Hinohikari and Akebono.岡山県平野部の主要水稲品種は，中生のヒノヒカリ，晩生のアケボノである．近年，夏期の高温障害が原因とされる乳白米，腹白米などのいわゆる白未熟粒の発生による玄米外観品質の低下が顕著となっており，その回避技術やより高品質，良食味品種の選択など，さまざまな対策が検討されている．このような背景のもと，1996年に九州地方において多収，良食味の観点から「にこまる」，「あきまさり」が育成された．にこまるはヒノヒカリと同等の熟期で極良食味であることに加えて，玄米外観品質が優れ，高温下における白未熟粒の発生が少ない品種である．一方あきまさりは，アケボノと同等の熟期で，ヒノヒカリ並みの食味を有する品種である．すなわち，これら２品種をヒノヒカリ，アケボノに替わる品種として導入することにより，より良食味で高品質米の生産が可能であると考えられる．著者らは，水田および畑圃場に温度勾配チャンバー（TGC）を設置し，温暖化による気温上昇を想定した作物（水稲，ダイズ，冬コムギ）の生産性を評価してきた．水稲（品種：日本晴）では，気温上昇によって不稔籾の増加することで減収となること，白未熟粒の発生によって玄米外観品質が低下することを報告した．また，気温上昇下での米飯の食味についても検討したが，その品種間差については検討を行っていない．本研究では，水田内に設置した TGC を用いて，移植から収穫に至る生育期間全体の気温上昇が，水稲４品種の収量，玄米外観品質，米飯の食味におよぼす影響の品種間差異を検討した