水稲根は,アンモニア態窒素を吸収したのち,直ちにアマイドならびにアミノ酸に同化する. 一方,サイトカイニンは,根部(根端)で生成され地上部へ移行し,葉身のN代謝などの制御に重要な役割をはたしているものと考えられている. しかし,根部におけるNの初期同化過程における根端ならびにサイトカイニンの役割について明らかにした報告はみられない. 本研究は,水稲分離根における¹⁵NH₄-N同化におよぼす根端の有無ならびにそれらにおよぼすサイトカイニン効果について調査したものである. 結果は次のごとくである. 1) 根端の切除は,遊離アミノ酸ならびに全蛋白区分への(¹⁵NH₄)2_SO₄からの¹⁵Nのとり込みをかなり低下させる. しかし,サイトカイニンを供給するとそれらへのとり込みは明らかに回復する. 2) 根端を切除した水稲根における¹⁵Nのとり込みにおよぼす数種のサイトカイニンの影響を検討すると,遊離アミノ酸ではBenzyladenine, Benzyladenosine, Zeatinなどが¹⁵Nのとり込みを高めている. 全蛋白区分では, Zeatin, Zeatin riboside, Benzyladenine, IsopentenyladenineなどがAdenineより¹⁵Nのとり込みを高めている. 3) 根端を切除した分離根における遊離アミノ酸のうちでグルタミンの¹⁵N含量は最も高く,アスパラギンのそれは低い傾向が認められた. サイトカイニンを供給するとアスパラギンを除く全てのアミノ酸の¹⁵N含量は高くなる. しかし,¹⁵Nとり込みパターンにおよぼす根端の有無ならびにサイトカイニン処理の影響は認められない. 4) 以上の結果から,水稲根におけるNの初期同化過程には,根端が密接に関連しており,おそらく根端で生成されるサイトカイニンが重要な因子として働いている可能性が示唆された.

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The great majority of upland fields in Japan are on plateau and hill-side where water permeability is high. Accordingly, upland crops frequently encounter drought injury in the dry season from July to August. To be resistant to drought injury, it is essential for upland crops to have roots deep in the soil where their roots can absorb nutrients and water effectively. This experiment was conducted to clarify that the root distribution of upland-cultured paddy rice (var. Myojoo) in the soil was influenced by tillage methods. The tillage methods used in this experiment are as follows: tillage by disk harrow at a depth of 10 cm after Mouldboard plowing at a depth of 25 cm, tillage by Rotavator at a depth of 17 cm, tillage by Screwvator at a depth of 30 cm. The results obtained are as follows: 1. Root distribution in the soil was influenced by tillage depth and physical soil properties. In Screwvator tillage, the roots distributed from the shallow layer to the deep layer of soil. In Rotavator tillage and in combination of disk harrow with Mouldboard plowing, the roots distributed only in the shallow layer. Soil strength by Mouldboard plowing was almost the same with the other tillage methods up to 10 cm from soil surface, but it was higher in the deeper layer than 10 cm. 2. There was no difference in top dry weight of upland-cultured paddy rice at 8th leaf stage between Rotavator tillage and Screwvator tillage. In Moudboard tillage, top dry weight was less than that in the above-mentioned tillage methods. This was due to high soil strength preventing the root growth. 3. Top dry weight at heading time was the greatest in Rotavator tillage, the second in Screwvator tillage, the third in Mouldboard plowing. This tendency continued to maturity stage. Reduction in top dry weight in Screwvator tillage was due to the penetration of roots into deep soil layer lacking in soil moisture. 4. Correlation coefficients between top dry weight and root dry weight were significant (r=0.733).

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イネ(O.prennis)および,トウモロコシ(Zea mays L.)の気孔の反応および,その光合成速度に対する酸素濃度の影響を検討した. その結果,強光下において炭酸ガスが存在する場合に,両者の気孔の高酸素濃度下での反応に著るしい種間差が認められた. すなわち,イネの気孔は,炭酸ガス濃度に関係なく,酸素濃度の影響をほとんどうけなかった. また,光呼吸のない0.22%CO₂濃度下においても,酸素濃度を増大させた場合には,5O%O₂以上で光合成速度は低下した. O.22%CO₂下における8O%O₂以下での光合成阻害量は,2O%O₂の時の光合成速度のほぼ20%であった. これは,気孔,光呼吸とは関係のない可逆性のある真の光合成の酸素による阻害と考えられた. 一方,トウモロコシにおいては,炭酸ガスのない空気中では酸素による気孔の閉鎖は認められなかったが,0.03および0.22%CO₂においては光が強くなるにつれて,また,酸素濃度が40%以上になると酸素濃度の増大につれて,気孔は閉鎖した. 強光下(0.3cal cm^-2min.¹,400-700 nm)において酸素濃度を80%にすると,光合成速度は20%O₂下での値の60%という大きな低下を示した. このトウモロコシにおける強光下の高酸素による大きな光合成の阻害はイネではみられない高酸素による気孔の閉鎖と,イネの光呼吸がない場合にもみられた可逆性のある真の光合成の阻害の相加効果によると考えられた. また,酸素による光合成阻害量と気孔の閉鎖割合の間には,一定の関係が存在し,高酸素濃度は,光合成阻害を通じて気孔閉鎖をもたらず可能性のあることが示唆された.

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Rice varieties from Hokkaido, Tohoku and Hokuriku were cultivated at different temperatures during the ripening period. The maximum viscosity of starch and yield of starch from milled riece which seemed to be the two main factors affecting the eating quality of the harvested rice were investigated. 1. Maximum viscosity of starch correlated most strongly with amylopectin content. And the lafger the amount of phytin in milled rice, the smaller the alkali decomposition of milled rice, and the fewer the appearance of milky white rice kernels, the higher was the maxlmum viscosity of starch, respectively. 2. Maximum viscosity of starch was increased by higher temperature during the ripening period. It was high in early varieties and palatable varieties. In amylogram, peak viscosity was correlated most signifiCantly with break down and significantly with rising temperature and minimum viscosity. Peak viscosity was negatively correlated most significantly with setback and significantly with consistency. 3. Amylose content was decreased by higher temperature during the ripening period. It was also low ln early varieties and in palatable varieties. At lower temperature, amylose content showed more highly negative correlation with maximum viscosity. 4. Phytin content in milled rice was increased by high temperature during the ripening period. It was also high in palatable varieties and in Hokkaido varieties. At low temperature, phytin content was lowly correlated with maximum viscosity. 5. The rice kernels of high alkali decomposition is estimated to be ripened at low temperature, because the degree of alkali decomposition was much higher when ripening temperature was lower. Within the same temperature of ripening period, the rice grains with lower maximum viscosity were more readily decomposed, and this tendency seemed to be due to the higher amylose content. 6. The occurrence of milky white rice kernels was negatively correlated with maximum viscosity of starch. White core rices occurred at high temperature and the percentages of white core rice appeared to be in parallel with the varietal difference of milky white rice kernels. 7. The starch yieid obtained from milled rice was negatively correlated with protein content, with high significance. The starch yield was low in the early or inferior taste varieties. 8. The amount of protein in milled rice was higher in the case of early varieties and small grain varieties. The starch of lower maximum viscosity was yielded from the rice grains ripened at lower temperature when compared at the same level of protein content.

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グレインソルガムの生長と窒素吸収パターンを明らかにするとともに,その生産性におよばす窒素施用の影響を調査した. 本試験ではグレインソルガム(交雑種,Hazera 726)を5段階の異なる窒素条件下(培地中窒素濃度,7.5,44,88,220および440ppm,ただし窒素吸収パターンを調べる試験では88ppm濃度を供試)で水耕栽培した. その結果,下記のことが明らかとなった. 1. 植物体新鮮重は生育が進むにつれて完熟期まで急激に増加するが,出穂から乳熟期にかけて一時的に増加速度が低下することが認められた. また,植物体の全窒素含量はいずれの部位においても令の進行に伴って低下するが,培地中窒素濃度が高いものほど高い値を示すことが収穫期に観察された. 生育に伴う窒素の吸収パターンは上記の植物体新鮮重とほぼ同一の傾向を示しており,グレインソルガムが生育過程中に2つの窒素要求の高い時期をもち,その時期は急激な茎葉の繁茂をおこす栄養生長期と子実の肥大期であることが認められた. 2. 植物体の生育量や子実収量は培地中窒素濃度440ppmにおいて最も高かったが,植物体や子実に吸収された窒素量は上記の濃度よりも高い濃度条件下で育てたものの方が高かった. 植物体乾物量に対する子実収量および植物体全窒素量に対する子実窒素量の比率によって示される子実の生産効率および子実窒素の生産効率はいずれも培地中窒素濃度17.5～88.0ppmの範囲内において比較的高い値を示していたが,それ以上の窒素濃度条件下では濃度の上昇に伴って低下した. 3. 子実の粗タンパク質含量は培地中窒素濃度の上昇に伴って著しく高まったが,粗脂肪含量などはほとんど培地中窒素濃度の影響を受けなかった. 最高の子実収量を示す培地中窒素濃度は子実の粗タンパク質含量や粗タンパク質収量が最高となる窒素濃度に比べて低いところに位置していた. 本試験の結果より,今後,子実収量と併行して子実の粗タンパク質含量を高める窒素の施用方法の検討が必要であると考えられた.

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イネ花粉の発育は,雄性不稔および花粉育種の観点から興味深い課題である. 本研究では,走査電子顕微鏡をもちいて,花粉の発育をその表面微細構造の変化の側面から研究した. またとくに,タペート細胞の表面構造変化と花粉の発育との関係についても注目した. 四分子期の小胞子の表面は,はじめ滑面であり,この時期のタペート細胞の表面も同様に滑面の構造を示すが,のちに小胞子表面に多数の粒状構造が現われると,タペートの表面にも,この細胞からの分泌物と考えられる隆起が見られ,さらに球形あるいは楕円形の構造が表面に付着するようになる. 花粉の発育が進み,発芽孔をタペート細胞に密着させて花粉が葯壁にそって並ぶ時期になると,花粉表面に物質が集積する. さらに花粉が成熟すると,花粉表面に粒状体,または2ないし4個の粒状体が集まった構造が見られる. この時期のタペート細胞の表面には,小さなとげをもった球状体(Orbicule)と思われる構造が多数現われる. 以上の如き観察結果から,小胞子および花粉の表面とタペート細胞の表面構造との関係を,花粉の発育に関連して論議した.

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1. Extremely early maturing barley, Saikai-kawa 24, was sown Sep. 1 and Sep. 8 in 1978 at Kyushu Natl. Agric. Exp. Stn., Chikugo, Fukuoka. Seed rate was 400 kernels/m². Seed was drilled. The distance between the rows was 18 cm. The field was irrigated occasionally. Plants grew vigorously. Grain matured and was harvested in late Dec.-early Jan. Aphid, leaf miner and cutworm were controlled by insecticides. No serious diseases were observed. The area of 0.216 m² (3 rows × 40 cm length) × 2 were harvested every 2 weeks excluding roots and the changes in the growth were traced. 2. Seed germination and seedling establishment were good. Plants headed 44-45 days after sowing. Culm length was 53-64 cm. Total dry weight (excluding roots) estimated by harvesting 1.62 m² (3 rows × 3 m length) × 2 was 60.0-91.1 kg/a and grain weight was 32.1-43.4 kg/a. Total weight increased rapidly from 2weeks before heading to 6 weeks after heading. On 84 days after sowing (Sown Sep. 1: Nov. 24, sown Sep. 8: Dec. 1), total weight was near to the maximum value. Plants sown Sep. 8 grew better than those sown Sep. 1. Plants topdressed (basal dressing, 1.0 kg nitrogen/a, plus topdressing, 0.5 kg nitrogen/a) grew better than those not topdressed (basal dressing 1.0 kg nitrogen/a, only). 3. Maximum LAI was 3.30-6.13. Mean CGR during the rapidly growing period (Sown Sep. 1: Sep. 30-Nov. 24, sown Sep. 8: Oct. 7-Dec. 1) was 11.3-19.1 (g/m²/day). Mean CGR of 84 days after sowing was 8.1-13.9. NAR before heading was 4.32-7.76(g/m²/day). RGR before heading was 0.095-0.156 (g/g/day). The efficiency of solar energy utilization (Eu) was estimatcd calculating (dry matter production × 4000 cal/g)/(solar radiation). Mean Eu during the rapidly growing period was 1.63-2.93%. Mean Eu of 84 days after sowing was 1.09-1.99%. LAI, CGR and Eu values of plants sown Sep. 8 or topdressed were higher than those of plants sown Sep. 1 or not topdressed. 4. The values of CGR, RGR, NAR and Eu of late-summer sown barley were nearly as high as those of other high yielding summer crops and rapidly growing winter barley. It is concluded that the high dry matter production of late-summer sown barley was obtained because of the high growth rate resulting from the efficiently utilized solar energy and the high net assimilation rate from the beginning of the growth.

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The numbers of late metaxylem vesstls and protophloem sieve tubes were observed at the root tips as well at the mature regions of rice crown roots. Protophloem sieve tubes were selected, because their number usually represents those of other conductive elements of the root, i.e. protoxylem vessels, early metaxylem vessels and metaphloem sieve tubes, respectively. 1. In the case of lower roots, the numbers of vessels and sieve tubes increase towards the higher "shoot units", reaching their highest values nearby the X-th "shoot unit" and decreasing above it. On the other hand, a reverse tendency was found in the case of upper roots. 2. In any root, the numbers of vessels and sieve tubes decrease acropetally. 3. The observation at the mature regions of the all roots revealed intimate correlations between numbers of vessels and sieve tubes and each of root diameter, stele diameter and pericycle cell number. However, only upper roots showed such intimate correlations, while lower roots did not. 4. Quite the same close correlations were found at the root tip where vessels and sieve tubes differentiate. 5. The diameter of the stele increases basipetally and sooner or later comes up to the constant value. And that value is in a high correlation with each of the stele diameter at the positions where vessels and sieve tubes differentiate. From observations mentioned above, it is thought that the numbers of vessels and sieve tubes may primarily be attributable to the dimensions of the part where these tissues differentiate, and that the later development of each tissue of a root may, in general, takes place in keeping pace with one another. It is furthermore suggested that the development and function of lower roots may not always be the same as those of upper roots.

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To make clear the action of ethylene in the growth of rice seedlings, three experiments were carried out as follows. First, growth of coleoptiles and seminal-roots of different types of rice varieties were tested. Second, the interaction of ethylene and ABA in the growth of rice seedlings were tested. Finaly, the ethylene evolution from soaked seeds was actually measured and its effects on the growth of rice seedlings under different seedlng density was examined. The results obtained were as follows. 1. Elongation of coleoptiles was promoted whereas the growth of seminal-roots was inhibited with ethylene treatment. 2. Diffefent varieties were found to respond differently to the ethylene treatment; coleoptiles of Japonica varieties and seminal-roots of indica varieties were more sensitive than the others. 3. Elongation of the coleoptiles was promoted by 10 ppm of ethylene combined with 1 ppm of ABA. 4. Interaction of ethylene with ABA in the elongation of mesocotyls was also recognlzed . 5. Ethylene concentration was increased in high seeding density and it promoted the elongatlon of coleoptiles.

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Using the rice varieties grown under pot cultivation, we investigated the effect of nitrogen top-dressing at full heading time on the distribution of nitrogen among the different organs and discussed about the translocation of nitrogen from other organs to the ear. The results are summarized as follows: 1. The nitrogen content of the leaf blade on the control (non top-dressed) plot decreased rapidly with time throughout ripening period. The nitrogen content of the leaf blade on the treatment (top-dressed) plot increased temporarily after top-dressing. Although it decreased thereafter continuously till maturing stage, the nitrogen content of the leaf blade at maturing stage showed more than double of that on the control plot. 2. The nitrogen content of the leaf sheath and the culm gradually decreased after full heading time on both plots. The nitrogen content of the leaf sheath and the culm at maturing stage on the top-dressing plot was nearly equal or rather superior to that at full heading time, because their nitrogen content as well as that of the leaf blade increased temporarily after top-dressing. 3. The nitrogen content of the ear on the top-dressing plot increased rapidly compared with that of the control plot and the nitrogen content of the ear at maturing stage was 1.4∼1.8 times more than that on the control plot. It seemed that this fact did not depend on the difference of ear weight but was caused by the difference of nitrogen percentage of the ear on both plots. 4. Most of the nitrogen contained in the ear at maturing stage on the control plot seemed to be translocated from the other organs, especially the leaf blade. The nitrogen absorbed from soil seemed to be only a very small amount in the nitrogen of the ear on the control plot. The nitrogen absorbed after top-dressing on the treatment plot seemed to be a large amount of the nitrogen contained in the ear and it corresponded to 58∼74 percent of the nitrogen content of the ear at maturing stage. The nitrogen content translocated from the leaf blade to the ear on the treatment plot was about 14∼26 percent in the nitrogen of the ear at maturing stage and the nitrogen translocated to the ear from the leaf sheath and culm seemed to be negligible or nothing.

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lt is known that the protein content of rice is increased by the nitrogen top-dressing at full heading time. The present experiments were carried out to clarify the varietal differences of the effect of nitrogen top-dressing at full heading time on the protein content of rice. Twenty varieties used in the experiments are those being cultivated or having been cultivated in Tohoku and Hokkaido districts. The summary of the results is shown below. 1. The protein content of brown rice of the varieties used in the experiments increased 8∼24 percent compared with that of the control (non top-dressed) plot by nitrogen top-dressing at full heading time. 2. The protein percentage of brown rice showed the positive correlation with the nitrogen percentage of the leaf blade at full heading time on the control plot and with the nitrogen percentage of the leaf blade at 10th day after top-dressing on the treatment plot. The protein percentage of brown rice showed the negative correlation with the nitrogen percentage of the leaf blade at the time of harvesting regardless of top-dressing. These facts seem to suggest that the better the translocation of nitrogen from the leaf blade to the ear, the higher the protein percentage of brown rice. 3. It is assumed that the difference among varieties of the increasing of protein percentage of brown rice by the nitrogen top-dressing at full heading time is rather due to the difference of distribution ratio of nitrogen to the ear than the difference of the amount of nitrogen absorbed.

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1977年にH-726を供試して,土壌乾燥や萎凋がグレインソルガムの生育,窒素の吸収,収量その他の特性におよぼす影響を調査した. テンショメーターを用い4葉期から生育の全期間,土壌水分を夫々pF0～1.5,0～2.0,0～2.5,0～2.8に保つ処理をした. 6葉出葉期から4日,8日,12日と4日ずつ増加した9区の乾燥処理をし,その前後は無処理区と同様に毎日灌水した. また,9葉期,12葉期,出穂期,出穂後10日の各期に灌水を中止し,初期萎凋になった時,継続的萎凋になった時,更にその3日後,及び6日後に再び無処理区と同様に灌水して萎凋の処理をした. 得られた結果は次の通りである. 1. グレインソルガムは圃場容水量を下まわらない充分な灌水で不充分な灌水より穀実や茎葉の収量があがり,蛋白質も増加した. 2. 継続的萎凋かそれ以上の土壌乾燥は生育や穀実及び茎葉の収量,蛋白質含量を著しく減少させたが,穀実の澱粉含量には見るべき差がなかった. 3. 生育の各期によって土壌水分に対する感受性が異り,生殖生長期即ち出穂期から開花期登熟初期は危険な時期で充分な土壌水分が要求され,十分な灌漑が必要である. 従って実際の栽培では水管理をよくし,これ等の期間の土壌水分不足はさけねばならない. 4. 出穂期に水分不足になれば花柄の伸長が阻害され,登熟初期の水分不足では穂重,1穂粒数,1穂粒重,千粒重も減じたが,穂長に影響はなかった. 5. 萎凋中に伸長する諸器官の伸長は減少し,反対に再灌水後に伸長する諸器官の発達が著しく増大することは興味あることで,節間の場合に,より明瞭であった. 6. 伸長しなかった根と伸長した根の合計値は灌水量の多い区,6葉期に10日程乾燥処理をした区で無処理より大きかった. また有意差はなかったが生育の各期で軽度の萎凋処理によって伸長した根が増し総根数も増大した. これは特に9葉期の処理で明らかであった. 7. グレインソルガムが生育初期(6葉期)のおよそ10日間の乾燥で,萎凋する前に灌水したもの,そして更に生育が進んで9葉期や12葉期に初期萎凋を経過したものが無処理区より生育が盛んになり,収量が増大したことは興味深いことで,これはおそらく充分な水湿と通気のため根のよりよい伸長と分布をもたらせたためと考えられるが,更に今後の研究にまたねばならない.

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It was clarified in the previous paper that a positive correlation existed between nitrogen content in leaf blades on the different position of the stem and stomatal aperture at different growth stages by using rice plants supplied with different nitrogen level. The aboye result suggested that the increase in stomatal aperture due to higher nitrogen content ln leaf blades affected the photosynthetic rate, considering a high positive correlation between stomatal aperture and photosynthetic rate. The present investigation was undertaken to examine the role of stomatal aperture and conductance on the increase of photosynthetic rate in relation to nitrogen content in leaf blades. The rice plants with different nitrogen content were prepared by additional application of ammonium sulfate to soils several days before the measurement of photosynthetic rate in gasmetric system by using infrared gas analyzer. Stomatal aperture and conductance on the same leaf blades used for the measurement of photosynthesis was measured by improved infiltration method and by diffusive resistance meter, respectively. The results obtained are as follows. A positive correlation was found between nitrogen content in leaf blades and photosynthetic rate, but the photosynthetic rate varied to some extent even in leaf blades with the same nitrogen content probably due to the difference of stomatal aperture and conductance. A high positive correlation was clarified between stomatal aperture or conductance and the photosynthetic rate in leaf blades with much wide range of nitrogen content. These results indicated that the photosynthetic rate increased due to the increase in the stomatal aperture and conductance in leaf blades with higher nitrogen content. Furthermore, a positive correlation was found between nitrogen content and photosynthetic rate in leaf blades with the same stomatal aperture and conductance only when the extent of stomatal opening was sufficient. The incline of the regression line in Fig. 3 and 7 was smaller compared with that in Flg. 1 and 5, respectively. That is, the increase in the photosynthetic rate due to the increase in nitrogen content was comparatively small in leaf blades with the same stomatal aperture and conductance. Mesophyll conductance was positively correlated with nitrogen content in leaf blades, especially with lower nitrogen content. From these results mentioned above, possible two fhctors are considered for increase in photosynthetic rate in relation to nitrogen content; the one is the increase in the chloroplast activity in CO₂ fixation and the other, the decrease in the resistance to CO₂ transfer from the atmosphere to mesophyll due to the increase in the stomatal aperture and conductance.

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It was suggested in the previous paper that the photosynthetic rate in leaf blades with higher nitrogen content increased not only due to the increase in chloroplast activity in CO₂ fixation, but also due to the decrease in the resistance of CO₂ transfer from atmosphere to mesophyll in relation to the increase in stomatal aperture and conductance. The present investigation was undertaken to ascertain the above suggestion by comparing between the photosynthetic rate measured with the infrared gas analyzer and that measured with the oxygen electrode. The photosynthetic rate in gasmetric system is much affected by stomatal aperture and conductance, while it is considered that the photosynthetic rate in liquid substrate is little affected by stomatal resistance on CO₂ absorption in mesophyll because CO₂ is absorbed mainly through the cut surface of the leaf slice. The photosynthetic rate, diffusive conductance and stomatal aperture in gasmetric system were positively and closely correlated with nitrogen content in leaf blades. A high positive correlation was found between diffusive conductance or stomatal aperture and photosynthetic rate in leaf blades with wide range of nitrogen content. These results indicate that the photosynthetic rate increased due to the increase in the diffusive conductance and stomatal aperture in leaf blades with higher nitrogen content as reported in the previous paper. The photosynthetic rate in the substrate with the concentration of 20 mM NaHCO₃ was positively correlated with nitrogen content in leaf blades. The increase of nitrogen content in leaf blades from 7.1 to 19.1 mg/dm² increased in the photosynthetic rate measured with the infrared gas analyzer by 2.5 times, while it increased in the photosynthetic rate measured with the oxygen electrode by 2.0 times. To examine the obtained data in detail the increase in the photosynthetic rate was compared in leaf blades on the same position of the stem. The incline of regression lines of the data measured with the gas analyzer were much larger in 2nd, 3rd and 4th leaf from the first expanded leaf, compared with those measured with the oxygen electrode. It is suggested that the difference between the incline of the two regression lines of the same leaf position indicated the influence of the stomatal aperture and diffusive conductance on the increase in photosynthetic rate with the increase in nitrogen content in leaf blades.

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In the previous report, a large difference was found between the leaf water potential(Ψ₁) measured by the thermocouple psychrometer and the xylem water potential (Ψ_x) measured by the pressure chamber under intense transpiration in the rice plant, and the water status in transpiring leaves was discussed. The present study was conducted to investigate the interrelations of Ψ₁ and Ψ_x among leaves on the different position of a stem or portions in a leaf blade in the rice plant and corn and to discuss the water condition of xylem and mesophyll cells in plants. The results obtained are as follows: Close agreement between Ψ₁ and Ψ_x was obtained in the dark room or under severe water stress with deficient moisture in soil, that is, under practically no transpiration, over wide range of water potential. With sufficient moisture in soil both under sunlight and artificial light, that is, under intense transpiration, Ψ_x was much lower than Ψ₁. These relations between Ψ₁ and Ψ_x were also recognized in the previous report. Furthermore, close correlation was found between transpiration rate and Ψ₁, and between transpiration rate and Ψ_x, but Ψ_x was lower than Ψ_l for a given increase of transpiration rate. With sufficient moisture in soil, independently of low Ψ_x of other leaves exposed to the sun even on a same stem, Ψ_x of the shaded leaves became as high as that when a whole plant was shaded, and independently of low Ψ_x of the apical part of a leaf blade exposed to the sun even in a same leaf, Ψ_x of the shaded basal part of a leaf blade became as high as that when a whole leaf was shaded. But under severe water stress with deficient moisture in soil, Ψ_x of the shaded leaf and the shaded basal part of a leaf blade remained as low as Ψ_x of other exposed leaves and the exposed apical part of a leaf blade, respectively. Interesting enough was the fact that even with sufficient moisture in soil, Ψ_x of the shaded apical part of a leaf blade was higher by only one or two bars than that of the exposed basal part of a leaf blade, and was considered to be affected by the latter. From these results, it is considered that negative pressure in vessels due to transpiration is hardly transmitted to the parts of a plant in reverse direction of transpiration stream, and negative pressure in vessels due to low root water potential or transpiration is transmitted to the parts of a plant in direction of transpiration stream away from the water resources. Ψ₁ of a shaded leaf of a given leaf position on a stem on which all leaves of other leaf position were exposed to the sun was lower than Ψ₁ of the leaf of the same leaf position when a whole plant was shaded. And even if any part of a leaf blade was shaded, Ψ₁ of a shaded part of a leaf blade was almost equal to Ψ₁ of the other part of a leaf blade exposed to the sun. Therefore, it is considered that Ψ₁ of organs or tissues was interrelated with that of other parts of a plant. Furthermore, it was recognized that, though Ψ_x ofleaves under intense transpiration was practically equal to Ψ_x of leaves under water stress with deficient moisture in soil, Ψ₁ of the former was much higher than Ψ₁ of the latter. From the results mentioned above, it is considered that the pressure chamber can be used only for the leaves without transpiration to estimate leaf water potential, and that using the pressure chamber to measure leaf water potential under condition of intense transpiration may give an erroneous result. [the rest omitted]

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