Study on the respiration of crop plants. : (4) Effect of 2, 4-D on the respiration of plants.

摘要

Experiments on wheat seedlings have been reported already. In the present report, soybean seedlings are used as material. Soon after the spray of 2, 4-D, abnormal increase in respiration is observed : maximum increase is about 50% over that of control plant (Table 1). We found that a whole plant does not die at the same time ; cotyledon and lower part of hypocotyl are more resistant but the uper half of hypocotyl is distinctly more susceptible to 2, 4-D. Then we separated a plant into, three parts and measured their respiration. Contrary to our expectation, respiration increase in the susceptible part is not really greater than that of resistant parts (Table 2). Nexttime, seedlings were separated into three parts, as above, before treating with 2, 4-D, and their respiration was measured with two hours' interval (Fig. 1). Respiration of susceptible part is originally higher than that of resistant parts but if it is cut off and separated from the other parts of the body, its respiration decreases suddenly, indicating that the original high rate of respiration is possible only when the enough food material is available in the tissue. The active tissue, respiring vigorously, based on the continuous supply of food material from the other tissues, should be most susceptible to 2, 4-D, because the increase of respiration will cause a drastic exhaustion of the tissue unless the transport of food is also promoted by 2, 4-D.