5-methyltryptophan (5MT) 저항성 벼 (Oryza sativa L. val. Sasanishiki)로 부터 선발된T-RI의 자식후대개체 중에서 저항성이 우성형질로 분리된 TR75주를 이용하여 그 식물체의 여러 특성을 조사하였다. 그 결과를 요약하면 다음과 같다. 1. TR75는 종자, 근, 약에 있어서는 25 mg/1의 5MT가 포함된 MS배지에서 callus가 형성되었으나, 야생형의 경우에는 어느 기관에서도 Callus 유도는 일어나지 않았다. 2. 각 기관으로 부터 유도된 TR75의 callus는 50mg/1의 5MT배지에서도 저항성을 보여주었지만 야생형의 callus는 25mg/1의 5MT 배지에서 모두 갈변화 하였다. 3. TR75는 3종류의 아미노산 아날로그(L-azetidine-2-carboxylic acid, S-2-aminoethyl-L-cystene, p-fluoro-DL-phenylalanine)에 대해서는 저항성을 갖고 있지 않다. 4. TR75의 유리아미노산 함량은 야생형 종자에 비해 tryptophan, phenylalanine, aspartic acid가 각각 5.0, 5.3, 2.7 배 증가하였으며, 그 외 다른 종류의 아미노산 함량도 1.5∼2.0배 증가하였다. 전 아미노산 함량도 약 1.5배 가량 증가하였다. 그러나 alanine과 leucine은 약간 감소하였다.

The inhibitory effects of mercury ions on the growth of barley seedlings were studied and the distribution of metal elements in the organs of treated plants was investigated by using synchrotron radiation induced X-ray emission (SRIXE). Although the treatment of mercury ions caused growth inhibition, the mercury-specific increase in variable fluorescence and the abolishment of energy-dependent quenching in broken barley chloroplasts as shown by Moon et al. (1992) were not observed in the leaves of growth-inhibited seedlings. Instead the treatment of mercury decreased Fmax and Fo values. However, Fmax/Fo ratio and photochemical and nonphotochemical quenching coefficients were not affected significantly. By SRIXE analysis of 10μM mercury chloride treated seedlings, accumulation of mercury in roots was observed after 1 hour of treatment and similar concentration was sustained for 48 hours. Relative contents of mercury was high in roots and underground nodes where seeds were attached, but was very low in leaves. Iron and zinc were also distributed mainly in the lower parts of the seedlings. However after 72 hours of treatment the contents of these metals in roots decreased and their distribution became more uniform, which may lead to death of the plants. These results suggest that the observed inhibitory effects on barley seedlings upto 48 hours after the treatment is not due to direct damages in the photosynthetic apparatus, but due to its accumulation in roots and the consequent retardation of the growth of barley seedlings. The decrease in Fmax and Fo is probably due to the decrease in chlorophyll and protein contents caused by the retardation of growth. The observed slow expansion of primary leaves could be also explained by the retardation of growth, but the fluorescence induction pattern from the leaves did not show characteristic symptoms of leaves under water stress.

To find heavy metal-specific effects on the photosynthetic apparatus of higher plants, we investigated effects of CuCl_2, HgCl_2 and ZnCl_2 on electron transport activity and chlorophyll fluorescence induction kinetics of chloroplasts isolated from barley seedlings. Effects on some related processes such as germination, growth and photosynthetic pigments of the test plants were also studied. Germination and growth rate were inhibited in a concentration-dependent manner by these metals. Mercury was shown to be the most potent inhibitor of germination, growth and biosynthesis of photosynthetic pigments of barley plants. In the inhibition of electron transport activity, quantum yield of PSⅡ, and chlorophyll fluorescence induction kinetics of chloroplasts isolated from barley seedlings, mercury chloride showed more pronounced effects than other two metals. Contrary to the effects of other two metals, mercury chloride increased variable fluorescence significantly and abolished qE in the fluorescence induction kinetics from broken chloroplasts of barley seedlings. This increase in variable fluorescence is due to the inhibition of the electron transport chain after PSⅡ and the following dark reactions. The inhibition of qE could be attributed to the interruption of pH formation and de-epoxidation o1 violaxathin to zeaxanthin to thylakoids by mercury. This unique effect of mercury on chlorophyll fluorescence induction pattern could be used as a good indicator for testing the presence and/or the concentration of mercury in the samples contaminated with heavy metals