Arrhenius plots of dynamic states of water in various crop plant organs exposed to cold or heat stress were studied by using ¹H-NMR. In chilling sensitive plants, phase transition in NMR spin-lattice relaxation time (T₁) occurred at 7.5°C and at 12.5°C in Vigna radiata and V. mungo hypocotyls, respectively, while that in spin-spin relaxation time (T₂) occurred at 13.5°C in sweet potato tubers. On the other hand, phase transition in T₁ occurred at 0°C in both leaves and roots of perennial ryegrass and pea epicotyls. Prolongation of T₁ was observed after the break point in these species. Furthermore, phase changes in T₂ of the ryegrass leaves and roots occurred at -20°C and -10°C, respectively. Judging from electrolyte leakage and viability test as well as T₂, both vacuolar and cytoplasmic compartments froze between -20 and -25°C in the leaves while the freezing in the root tissues occurred between -10 and -15°C in ryegrass. Therefore, supercooling ability of the ryegrass organs were especially detected by T₂. On the other hand, adaptation to heat stress was clearly shown by T₁ while heat-denature was shown by a marked decrease in T₂. From these results, the phase transition temperatures were closely correlated their stress sensitivity, especially acclimation to temperatures was detectable by T₁ while critical temperature by T₂. In conclusion, analysis of Arrhenius plots of T₁ and T₂ in plant organs provided sensitive and non-invasive way for evaluating both primary and lethal responses to the temperature stresses.

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ブドウ‘巨峰’果実は高温条件下で生育すると着色不良となることが知られている.高温条件下におけるアントシアニン生合成の制御機構を解明するため, 異なる温度条件で生育した果実を用い, フラボノイド含量, アントシアニン代謝, 関連酵素活性, 光合成産物の転流・分配を調査した.昼夜30℃一定条件で生育した果実では, 昼夜25℃一定, 昼温30℃/夜温15℃で生育した果実と比べ, 果皮中アントシアニン含量が著しく低下した.同様に, アントシアニンの前駆体であるフェニルアラニンも30℃で生育した果実で蓄積量が劣っており, 果実への光合成産物の転流量も減少した.フェニルアラニンアンモニアリアーゼ (PAL) 活性は25℃で生育した果実で高かったが, UDPグルコースフラボノイド3-O-グルコシルトランスフェラーゼ (UFGT) 活性は低夜温の30/15℃で生育した果実で高かった.以上の結果から, 高温条件下で生育した‘巨峰’果実では, 光合成産物の分配の減少, 果皮中のフェニルアラニン蓄積不足, およびUFGT活性の著しい低下によってアントシアニン生合成が阻害されることが示唆された.

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イネ幼苗は内分泌撹乱作用物質と考えられるビスフェノールA (BPA) を速やかに吸収し, 水質を浄化した.BPA添加養液で栽培したイネ幼苗を経時的に収穫し, エタノール洗浄による根表面, メタノール抽出による根と地上部 (茎葉部) に存在するBPAをHPLCで定量したところ, BPAは根より吸収され, 地上部に転送されることが判明した.植物体からBPAの回収率が低かったので, 重水素化したBPAを吸収させ, 根と地上部に存在する代謝物を²H-NMR測定で検索した.BPAに換算して, メタノールで抽出できる代謝物量は投与量の約5%, 酸あるいはアルカリによる加水分解で遊離する代謝物量は約25%で, 残り (約70%) は, 上述の加水分解条件では遊離しない重合体あるいは植物体との結合を形成すると判断された.可溶化した代謝物の²H-NMR分析から, 吸収されたビスフェノールAの一部は酸化あるいは炭素骨格の変換等によって代謝されると推定された.

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Seedlings of three tree species, Japanese cedar, red pine and beech, grown in plastic green houses were subjected to a simulated acid fog adjusted to pH values of 2, 3 and 4 and to distilled water (the control), during the growing season from 1998 to 2001, and effects on visible injury, growth, foliage chlorophyll and nitrogen contents were studied. In cedar and pine, an increase in total dry weight (TDW) was accelerated by acid fog of pH2 and pH3 with increasing duration of treated years, although a trend of growth inhibition of TDW was observed in beech. The stimulated growth in cedar of pH2 and pH3 plots resulted in death of 29 to 45% of plants. Foliage nitrogen and chlorophyll content in beech were severely affected than in cedar and pine. On the other hand, foliar injury in pine and cedar by acid fog exposure was higher in lower pH plots and the injury increased with increasing duration of treated years. In contrast, in beech, the injury increased with the decreasing acid fog pH, but wasn't accelerated by increase in duration of treated years. Thus, response of tree seedlings to simulated acid fog was found to be quite complex depending on species and duration of treated years.

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シンビジウム (Cymbidiumt Twilight Moon‘Day Light’) のプロトコーム状球体 (PLB) 切片からのカルス誘導, カルス増殖およびカルスからのPLB形成に及ぼす赤色および青色発光ダイオード (LED) 光源の影響について調査した.まず, カルス誘導に及ぼす光源の種類および赤色/青色LED混合比の影響を調査するため, 100ml容三角フラスコ内の修正Vacin・Went寒天培地 (0.1mg1^-1NAAおよび0.01mg1^-1TDZ添加) 上にPLB切片を置床し, 種々の混合比 (赤色100%, 赤色75%+青色25%, 赤色50%+青色50%, 赤色25%+青色75%, および青色100%) のLED光源下および植物育成用螢光灯 (PGF) 下で培養した (いずれも16時間照明, 45μmol m^-2s^-1 PPFD) .その結果, PLB切片からのカルス誘導には赤色100%LED光源が最も有効であることが明らかとなった.また, カルス増殖は赤色75%+青色25%LED光源下で促進されたが, PGF光源下での反応と比べ有意差はなかった.これに対し, カルスからのPLB形成は赤色25%+青色75%LED光源下で最も促進された.以上のことから, LED光源はシンビジウムPLB切片からのカルス誘導, カルス増殖およびカルスからのPLB形成に対して有効であることが明らかになった.

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Grafted tomato (scion : Lycoperisicon esculentum Mill. cv. Momotaro ; rootstock : cv. Helper M) plug seedlings were stored at 10°C for 21 d under photosynthetic photon flux density (PPFD) of 2μmol m^-2s^-1 using mixed light from red and blue light LEDs, with different red/ blue PPFD ratios (100/0: R100, 97/3 : R97B3 and 50/50: R50B50) . The stored seedlings were transplanted and cultivated for 14 d at 25/18°C (day/night) and 300μmol m^-2s^-1 PPFD. The seedlings in R100 tended to lose their dry weight (DW) during storage, while those in R97B3 and R50B50 did not. On the last day of the storage, the contents of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) and chlorophyll tended to be greater with decreasing the red/ blue PPFD ratio. However, there was no difference in DW of tomato plants at the last day of cultivation among the treatments. These results indicated that the difference in the contents of Rubisco and chlorophyll caused by different red/blue PPFD ratios did not affect the growth during cultivation following the storage. On the last day of the storage, the contents of carbohydrate were extremely small in all stored seedlings irrespective of the red/blue PPFD ratios. They may lead to no difference in the growth of tomato plant during cultivation following the storage. However, blue light mixing both in R97B3 and R50B50 was effective for maintaining DW and the visual quality due to the greater chlorophyll content during the low temperature storage of grafted tomato seedlings.

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Effects of vernalization and photoperiod on inflorescence formation in radish (Rahpanus sativus L.) were investigated. Plants were exposed to photoperiods (8, 12, 16 or 24 hr) during or after low temperature treatment (6°C), respectively. We used a new index “flower formation index” to explain these effects on inflorescence formation in radish plants quantitatively. According to “flower formation index”, the inflorescence formation was suppressed under the condition of short photoperiods, and increased under the condition of long photoperiods after the low temperature treatment as compared with that during the low temperature treatment. The suppression of inflorescence formation markedly occurred at short photoperiod treatment of 20-30 days after 7 days low temperature treatment, but the tendency was decreased in 21 days low temperature treatment even if the short photoperiod treatment was extended until 40 days. It was supposed that the short photoperiod treatment could be available to suppress a part of the inflorescence formation in the time of low temperature induction in the field.

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The physiological accommodation response to environmental stress of a plant can induce changes in physiological and physical conditions of the plant. These changes influence the dielectric properties of the plant, which can be detected by measuring microwave complex dielectric properties of plant materials such as leaves and stems. The objective of this research was to detect these responses of plants to water deficiency stress nondestructively. The complex dielectric properties of tomato leaves during water stress were measured with an Open-ended Coaxial Probe from 0.3 to 3 GHz, as well as changes in gravimetric moisture, photosynthetic rate, stomatal conductance and water potential which reflect the physiological condition of the plants. Experimental results showed that the complex permittivity (both permittivity and loss factor) of tomato leaves increased during water stress. Of the parameters measured the highest correlation was observed between complex permittivity and water potential. In order to confirm these results, control and water deficient tomato leaves were crushed, and the complex permittivity was measured and compared. The results showed quite similar tendencies compared with the results from the nondestructive microwave measurements. A physiochemical model to describe the complex permittivity of crushed non-stressed and stressed tomato leaves was constructed with pure water, pulp, glycine, and KNO₃, and the complex dielectric measurements of crushed tomato leaves were reproduced quite accurately from 0.3 to 3 GHz.

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Symptom of high temperature injury of pale green and dark green leaves of Oncidium under the same sunlight condition was investigated. Although the flavonoid content in pale green leaves was larger than dark green leaves, carotenoid content, superoxide dismutase, ascorbate peroxidase, catalase activities and hydrogen peroxide content were smaller. However, by exposure to high temperatures (42°C maximum air temperature) for 4 days, 31% area of pale green leaves was sunburned, whereas dark green leaves were completely burned. Thus, the high temperature injury in pale green leaves was comparatively mitigated compared with that of dark green leaves in Oncidium plants.

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3種類の螢光ランプ (赤色, 青色および白色) を光源とし, PPFが10μmol・m^-2・s^-1, 夜間12時間補光した場合のトルコギキョウ苗の生長に対する光質の影響を調べた.‘つくしの雪’および‘SOパープル’とも, 青色光で最も生長が促進された.トルコギキョウ苗の生長は育苗期間中の青色補光により育苗期間を短縮する方法として有望であり, コストが低く, 発熱の少ない螢光ランプは育苗用の光源として現場での実用性が高いと考えられた.

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