抄録
The effects of heavy metals on ethylene release from plants were investigated and the possiblity of plant growth diagnosis by measuring the enthylene concentration in closed plant cultivation systems such as Controlled Ecological Life Support Systems (CELSS) was discussed. The ethylene release rate of intact lettuce plants (Lactuca sativa L. cv. Okayama) was increased by 0.34 mmol L-1 of Ni and 0.34 mmol L-1 of Co and decreased by 0.38 mmol L-1 of Cr and 0.31 mmol L-1 of Cu. Chlorophyll degradation in the leaves occurred in the unexpanded leaves in Ni treatment and in the expanded leaves in Co treatment. In these leaves, ethylene was mainly produced. No visible injury was observed in Cr and Cu. The time course of ethylene concentration was investigated in a closed chamber in which 12 lettuce plants were hydroponically cultivated with a nutrient solution containing 0.34 mmol L-1 of Ni. The ethylene concentration in the chamber started to increase 18 h after the beginning of the experiment. Thereafter, it continued to increase and the highest value (8.0 nmol h-1/plant) was observed 30 h after the beginning of the experiment. This change was more drastic than those in rates of photosynthesis and transpiration, and occurred earlier than appearance of visible injury by Ni stress. These results indicate that measurement of ethylene concentration in closed systems such as CELSS can be a useful non-destructive measurement method for plant growth diagnosis.
