変化する塩ストレス条件下における湛水の電気伝導度とイネの乾物生産低下の関係

　Knowledge about the relationships between the intensity of salinity of rooting medium and dry matter production may contribute to the improvement of rice yield under saline conditions. A rice cultivar Koshihikari was grown in pots with soils under submerged soil conditions. The stagnant water was salinized with NaCl from 31, 45 and 59 days after sowing, and for each of those, the level of salinity was increased every 6 days to maturity at three different rates of increase. Electrical conductivity (EC) of stagnant water was measured. Final dry weight of above ground parts and panicles decreased as initiation of salinization took place earlier and the rate of increase of EC was higher. Reduction in panicle dry weight was correlated with the occurrence of white heads. The values of EC at which plants died increased with the plant development and the rate of increase of EC, while these depended mainly on the rate of increase of EC but not on the time of salinization. In the plants which survived after heading, the final dry weight decreased in proportion to accumulated EC (sum of EC values for each day until harvest). Therefore, except for strong salinity where plants may die before heading, accumulated EC should be abe to predict dry matter production under salinity as an integrated indicator of level and duration of salinity.塩性環境における稲作改善のために，イネの乾物生産と根域の塩性程度との関係を知ることは重要である．水稲品種コシヒカリを用い，土壌を詰めたポットで湛水栽培し，湛水に塩化ナトリウム（塩）を添加することによって塩ストレスを与えた．塩添加は播種後31，45および59日目から開始され，それぞれ６日ごとに３段階の異なる速度で塩を添加するとともに，湛水の電気伝導度（EC）を測定した．地上部および穂の最終的な乾物重は，塩添加開始が早いほど，EC の増加速度が大であるほど低下した．そして，穂の乾物重は白穂の発生率が高いほど低下した．植物体が枯死したときの EC 値もまた，塩添加の開始時期が早いほど速度が大であるほど大きかったが，この EC 値は主にEC 増加速度に依存しており，塩添加開始時期の影響は小さかった．一方，出穂した植物で乾物重は積算 EC 値（毎日の EC の値を植物体採取日まで足した値）に対して直線的に低下した．以上より，出穂する前に枯死するような強い塩性環境を除けば，積算 EC 値は塩ストレスの強さと期間を総合した指標で，イネの最終的な乾物生産をよく予測すると考えられた

SAFETY AND EFFICIENCY OF XYLEM WATER TRANSPORT IN TWO CASHEW (Anacardium occidentale L.) STRAINS AT THE SEEDLING STAGE

ABSTRACTAs cashew trees are grown by transplanting seedlings, the seedlingoften suffers from drought damaged due to prolonged dry season. Previousstudy found that the ability to maintain water transport in xylem related todrought resistant character. To determine whether there was trade-offbetween the ability to maintain water transport in xylem and an efficiencyof water transport, differences in xylem vulnerability to dysfunction,hydraulic conductance, and the relationship to xylem vessel diameter wereexamined in two cashew strains. The xylem vulnerability to dysfunctionwas evaluated by the applied pressure which induced 50% loss of stemhydraulic conductivity (P 50 ). The hydraulic conductance on root, stem, andleaf were determined with High Pressure Flow Meter (HPFM). Variationsin the P 50 values were found between A3-1 and Pangkep, whereas thevalues were 1.75 and 0.50 MPa, respectively. However, since there was nodifference in the hydraulic conductance and the vessel diameter, the trade-off between the ability to maintain water transport in xylem and anefficiency of water transport did not occur in cashew. It was suggested thatgood combination of efficiency and safety of water transport enables A3-1to strongly uptake soil water either in dry or wet season resulting in goodadaptation to drought prone environment, and the P 50 value would besuitable parameter for evaluating drought tolerance of cashew at theseedling stage.Key words: cashew strain, vessel, xylem dysfunction, hydraulicconductance, droughtABSTRAKPengembangan jambu mete secara transplanting sering diikuticekaman kekeringan pada bibit akibat musim kering yang berkepanjangan.Studi awal memperlihatkan bahwa kemampuan xylem mempertahankanfungsi transportasi air merupakan karakter pertahanan penting terhadapcekaman kekeringan. Untuk mengetahui apakah terjadi kompensasi antarakemampuan pertahanan fungsi xylem dan tingkat efisiensi transportasiairnya dilakukan pengujian pada aspek kepekaan fungsi xylem, hantaranhidraulik, dan ukuran vesselnya. Kepekaan fungsi xylem ditentukan darinilai tekanan udara yang menyebabkan kehilangan 50% hydraulicconductance (P 50 ). Nilai hydraulic conductance pada akar, batang, dandaun ditentukan dengan menggunakan metode High Pressure Flow Meter(HPFM). Hasil pengujian menunjukkan terdapat perbedaan nilai P 50diantara dua strain jambu mete yang diuji, yakni secara berturut-turut 1,75dan 0,50 MPa pada strain A3-1 dan Pangkep. Karena tidak disertaiperbedaan pada hydraulic conductance dan ukuran vesselnya, makadisimpulkan tidak ditemukan nilai adanya mekanisme kompensasi antarakemampuan pertahanan fungsi xylem dan tingkat efisiensi pengangkutanair. Hal ini memungkinkan A3-1 tetap dapat menyerap air tanah secaracukup, baik pada musim kering maupun musim basah, dan mampuberadaptasi dengan baik di daerah rawan kekeringan. Dan nilai P 50 dapatdijadikan sebagai parameter representatif untuk evaluasi toleransi bibitjambu mete terhadap cekaman kekeringan.Kata kunci:  strain jambu mete, vessel, fungsi xylem, hydraulicconductance, cekaman kekeringa

Saline Irrigation using Ion-exchange Resin and Reverse Osmosis Membrane in Wheat and Barley

Saline irrigation equipped desaline apparatus in a root zone was tested to save fresh water resources. Pots of 56 mm inner-diameter and 40 cm in length were used. Amberlite (ion-exchange resin) and reverse osmosis membrane, both of which had a desalinating ability, were set at the bottom of each pot in desaline plots, respectively. In the control plot, a lovesheet (non-woven cloth) that had no ability to desaline was set. Wheat and barley were transplanted into these pots, which were filled with soil, and the pots were irrigated through the bottom either by fresh or saline water. The two crops responded to desaline methods and irrigation similarly. Growth and development in the two crops were suppressed largely by saline irrigation in the control plot. Amberlite did not affect the growth and development under fresh water irrigation. Shoot dry weight was increased by amberlite under saline irrigation, but the final values of sodium concentration of shoot and soil was not affected. The sodium concentration was reduced by reverse osmosis membrane, whereas the growth and development were suppressed under both fresh and saline irrigations. Amberlite and reverse osmosis membrane improved the growth and development and sodium concentration, but it should be a challenge to improve desaline ability of amberlite and water permeability of reverse osmosis membrane.塩水を農業用水として利用し淡水資源を節約するために，根域に除塩処理を施す塩水灌漑法を検討した．内径56㎜，長さ40㎝の塩ビ製のポットを用いた．ポットの底部には除塩効果があるアンバーライト（イオン交換樹脂）および逆浸透膜を設置する区と除塩効果がないラブシート（不織布）を設置する対照区を設けた．そしてポットに土壌を詰めコムギとオオムギを移植し，ポットの底から淡水および塩水で灌漑した．脱塩処理および灌漑に対する反応は２作物で同じであった．対照区では塩水灌漑によって生育が著しく抑制された．アンバーライト区で作物の生育は，淡水灌漑で対照区と変わらなかった．塩水灌漑ではアンバーライトによって乾物生産が対照区より向上したが，最終的な茎葉部と土壌のナトリウム含有率は対照区と変わらなかった．逆浸透膜は茎葉部と土壌のナトリウム濃度を低下させた．しかし逆浸透膜によって作物の生育は，淡水および塩水の二つの灌漑条件で対照区より著しく小さくなった．アンバーライトと逆浸透膜はともに除塩効果があった．しかし，アンバーライトは塩水処理能力の限界があること，逆浸透膜は水の移動が阻害されることが解決しなければならない課題であることが分かった

Changes of Rice Sodium Content due to Sodium Exclusion and Transpiration under Salinity

The relationship between sodium contents of tops and transpiration rates was studied in two rice varieties with different sodium exclusion rates in roots; Kala-Rata1-24(KR1;low exclusion rate) and IR28 (high exclusion rate). Seedlings at 7th leaf stage grown in culture solution were subjected to saline water(100mM sodium chloride) and transpired for 12 hours. Various transpiration rates were obtained under different humidity, light intensity and temperature conditions. Transpiration stream concentration factor of Na+ (TSCFNa+), which denotes the sodium exclusion rate in the root, decreased with increase in the transpiration rate under different humidity and light intensity conditions. On the other hand, TSCFNa+ was lower in KR1 than in IR28 under different temperature conditions. There were no different in the sodium exclusion rates at high transpiration rates. Sodium contents of tops initially increased with the transpiration rates but afterwards decreased with the transpiration rates. Sodium contents of tops were higher in KR1 than in IR28 at low transpiration rates under high humidity and low light intensity conditions, but it was higher in IR28 under low temperature conditions. There were no varietal differences in the sodium contents of tops at high transpiration rates. These results indicated that the varietal differences in sodium exclusion rates were detectable at low transpiration rates and affected the sodium contents of tops, but there were no differences in the sodium contents of tops at high transpiration rates.イネでは、ナトリウム（Na)含有率が高いほど光合成速度、苗の生存率および相対生長速度が低下することから、塩ストレス下における体内Na含有率の品種間差異に着目した研究が進められてきた。しかし、塩ストレスに対する体内Na含有率の品種による反応は、研究によって異なる。Makiharaらは、幼苗期にNa含有率が異なるとされる品種を成熟まで栽培したところ、Na含有率に大きな差異を見出さなかった。また、Makiharaらの研究でNa含有率が低かった品種が、森田らの研究では高かった。イネは、根においてナトリウムイオン（Na+）を分離排除する能力をもし、その程度は品種によって異なる。この能力は体内に入り込む水のNa+濃度に影響を与えるのが、体内に取り込まれるNa+の質は、流れる水の総量に影響される。すなわち、イネのNa含有率は、蒸散量と蒸散流に含まれるNa+濃度によって決まり、後者は根におけるNa+排除率によって変わる。蒸散と排除率はいずれも環境条件によって変わると考えられ、それによって体内Na含有率も変わるであろう。したがって、研究によってNa含有率の反応が異なるのは、両者の相互作用によると考えられえる。しかし、蒸散量とNa+排除率の変化が体内Na含有率にどのように影響を与えるのかは知られていないので、本研究で調べた

Growth and Sodium Accumulation in the Tillers which Appear on the Upper Nodes in Rice (Oryza sativca L.) Under Saline Conditions

The mechanism of late-grown tillers which come out of the upper culm nodes in rice (Oryza sativa L.) under saline conditions was examined. A rice cultivar, Akihikari was grown in pots under flooding conditions. The panicles were excised below the neck node of the panicle at the heading stage. Salinity treatment consisted of adding 100mM sodium chloride to water of pot at the excision of panicle (Na0), and 14 days after the excision (Na2). Tillers on the upper clum nodes grew in NaO and Na2. Dry weight of tillers increased with decrease of dry weight of stock shoots that produced the tillers. So the sum of dry weights of the stock shoots and tillers did not change, indicating that tiller growth apparently depended on reserve of carbohydrate in the stock shotts. Sodium was accumulated gradually in the plant, while sodium content of internode and tiller were kept lower than those of leaa blade and leaf sheath. In the leaf blade and leaf sheath, the upper organs accumulated less sodium than the lower organs. The tillers on the upper nodes grow faster and had low sodium content in the early stages of tiller development in NaO. Therefore, it was concluded that tillers which come out of the upper culm nodes could grow under saline conditions because the sodium content of tiller, internode and the upper leaf sheath were kept at a relatively low level.塩条件下において高節位分げつが成長する要因を調べた．水稲品種アキヒカリをポットに移植し湛水条件で栽培し，出穂期に穂を穂首節真下より切除した．ポットの水にNaCl濃度100mMとなるようにNaClを添加する処理を穂切除直後（Na０区）と14日後（Na２区）に行った．Na０とNa２区ともに高節位分げつが成長，乾物重が増加するとともに分げつを発生させた茎（母茎）の乾物重は低下した．分げつと母茎の乾物重の和は変化がなく，分げつの成長は母茎の貯蔵炭水化物によっていた．節間と分げつのNa含有率は葉身と葉より低く保たれ，葉身，葉鞘でも下位節に比べ上位節のNa含有率が低かった．またNa０区の分げつ成長初期では茎上部の分げつほど成長が早く，Na含有率が低かった．以上のことから塩条件下で高節位分げつが成長するのは分げつと乾物供給源である節間と上位葉のNa含有率が比較的低く抑えられるためであると考えられた

Xylem Dysfunction under Drought in Crop Plants

The xylem is a structure for long distance transport of water in land plants.Once cavitation occurs in the xylem vessel lumen due to negative pressure,the xylem may loose its ablity of water transpot,In genaral this vulnerability,i.e.xylem dysfunction due to negative pressure,is considered to be related to plants adaptation to various water environments.It was found that crop plants such as rice and soybean had highly vulnerable xylem,and that the lost hydraulic condubtance under drought was not recovered fully at re-watering in rice.Additional research is needed to examine whether maintenance of xylem hydraulic conductance under drought may improve drought resistance in crop plants陸上に生育する植物がどのようにして水を吸収するかは、古くから興味がもたれてきた。さまざまな説明が提案されてきたが、現在では、水の凝集力張力説が一般に受け入れられている。凝集力張力説では植物体内で水は凝集力によって連続した水柱、あるいは連続した水の綱として存在していると考える。葉からの水の蒸発すなわち蒸散のよって水分が失われると葉に負圧が生じ、この力で水の綱が引かれる。このように水の綱に加えられた張力によって水が引き上げられ、最終的に土壌から根を通って葉に至る連続的な水の流れが生じると説明される。そして、植物体内で最も長い距離の水輸送を担当するのが木部導管である。水が連続的に植物体内を流れるためには、導管内の水は張力に対抗する凝集力によって水柱を維持しなければならない。一般に、水に大きな負圧がかかると液体中に気泡が発生する空洞現象が起こる。導管内のみずに大きな張力（負圧）がかかるとやはり空洞現象が起こり、これによって形成された気泡が導管に広がると空気の塞栓となり、水の連続的な流れが止められる。空洞現象が実際に起こっていることは、Milburnによって1963年に音響学的に示された。空洞ができるときに発生する音をレコードプレイヤーで捉えたのであった。その後、空洞現象が負圧によって直接引き起こされるというより、導管の周囲に存在する空気が導管の隔膜を通して引き込まれるためであると考えられるようになった。同時に、空洞現象による木部導管水コンダクタンスの低下を測定する方法が開発された。この測定方法は、空洞現象によって発生した導管内の気泡が加圧した水を導管に通すことによって取り除かれることを利用している。5cmから30cmの長さで茎や葉柄を切り出し、切片の一方の切り口にビニール管をつなぎ低い水圧（約6kPa）で水を通し、反対の切り口に流れ出る水の量を測定する。これらの測定値から水コンダクタンスを計算することが出来る。次に導管内の気泡を取り除くために高い圧力（約170kPa）で水を通し、再び低い水圧で水コンダクタンスを測定する。もしも、切片の導管内に気泡が存在すれば、最初の水コンダクタンスの方が高くなる。この水コンダクタンスの増加部分が気泡による水コンダクタンスの低下とみなすことができる。そこで、気泡の発生程度は、気泡が無いときの水コンダクタンスに対する気泡による水コンダクタンスの低下割合、PLC（Precent Loss Conductivity）として表わす

The Effect of Prevention of Root Injury on Growth, Development and Dry Weight in Rice (Oryza sativa L.) Transplanted to Saline Soil

Rice root has an important role in water absorption and exclusion of sodium ion in saline soil. However, it is injured during transplanting to paddy field. The objective of this study was to examine whether prevention of such root injury reduces salinity damage in rice. Extremely early rice cultivar "Akihikari" that is not salt tolerant was grown in plastic bags filled with soil. Roots of seedlings were clipped leaving 5mm~10mm, then transplanted to 5L pots filled with soil applied with 0g, 7g and 10g of sodium chloride (NaCl). The growth and dry weight at the mature stage was compared to those of plants transplanted with intact roots. Time of transplanting was 12, 19, 26 and 33 days after sowing. Increase of number of stems was suppressed due to root clipping and salinity, but there was no interaction between the two factors. Dry weight of total above ground part and panicle decreased due to salinity though root clipping did not change them. The reduction of panicle dry weight was caused by the reduction of mean number of spikelets per panicle, thus mean panicle dry weight, as number of panicles and mean spikelet dry weight showed no changes. It was concluded that prevention of the root injury may not effectively alleviate salinity damage in less salt tolerant rice cultivars.イネの根は吸水するとともにナトリウムイオンを排除する役割を持っている．水田移植栽培において根の損傷を防ぐことが効果的に塩害を軽減するかどうかを検討した．耐塩性の弱いイネ極早生品種アキヒカリを用い，土壌を詰めたビニール袋で育苗した．苗の根を5 ㎜～10 ㎜ 残し切除して，塩化ナトリウム（NaCl）0ｇ，7ｇ，10ｇを土壌に添加したポットに移植し，根を傷つけないように移植した植物と生育と成熟期の乾物重を比較した．移植は播種後12日，19日，26日，33日の4回行った．茎数の増加は根の切除および塩添加によって抑制されたが，二要因の交互作用はなかった．成熟期の地上部と穂の乾物重は塩添加によって減少したが，根切除の影響はなかった．穂の乾物重の減少は穂数と平均1籾重が変わらなかったため，平均1穂籾数の低下による平均1穂重の低下によっていた．以上の結果から耐塩性が小さい日本の品種において移植時の根の損傷を防ぐことは，塩害軽減に効果的でないと考えられた

Behavioral phenotypes of mice lacking purinergic P2X4 receptors in acute and chronic pain assays

A growing body of evidence indicates that P2X receptors (P2XRs), a family of ligand-gated cation channels activated by extracellular ATP, play an important role in pain signaling. In contrast to the role of the P2X3R subtype that has been extensively studied, the precise roles of others among the seven P2XR subtypes (P2X1R-P2X7R) remain to be determined because of a lack of sufficiently powerful tools to specifically block P2XR signaling in vivo. In the present study, we investigated the behavioral phenotypes of a line of mice in which the p2rx4 gene was disrupted in a series of acute and chronic pain assays. While p2rx4-/- mice showed no major defects in pain responses evoked by acute noxious stimuli and local tissue damage or in motor function as compared with wild-type mice, these mice displayed reduced pain responses in two models of chronic pain (inflammatory and neuropathic pain). In a model of chronic inflammatory pain developed by intraplantar injection of complete Freund's adjuvant (CFA), p2rx4-/- mice exhibited attenuations of pain hypersensitivity to innocuous mechanical stimuli (tactile allodynia) and also of the CFA-induced swelling of the hindpaw. A most striking phenotype was observed in a test of neuropathic pain: tactile allodynia caused by an injury to spinal nerve was markedly blunted in p2rx4-/- mice. By contrast, pain hypersensitivity to a cold stimulus (cold allodynia) after the injury was comparable in wild-type and p2rx4-/- mice. Together, these findings reveal a predominant contribution of P2X4R to nerve injury-induced tactile allodynia and, to the lesser extent, peripheral inflammation. Loss of P2X4R produced no defects in acute physiological pain or tissue damaged-induced pain, highlighting the possibility of a therapeutic benefit of blocking P2X4R in the treatment of chronic pain, especially tactile allodynia after nerve injury