Protoplasmic streaming in root hairs of crop plants.

Abstract

1. An apparatus was devised to facilitate vital observation, without injury, of seedling roots of rice and several other crop plants under a microscope, and to measure the rate of protoplasmic streaming in the root hairs under various temperature conditions. 2. The rate of protoplasmic streaming increased with temperature in an exponential curve, but above certain temperature, the rate began to decrease. Between l0°C. and 25°C., Q10 values were 2.0 in rice plant and 1.6 in wheat plant. 3. The difference in the cultivating temperature (15, 20, 25°C.) before the measurement had no effect on the rate of streaming in rice plant. 4. The temperature at which the maximum streaming rate was observed differed with species of crop plants. In wellwater (pH 6.6), it was 33°C. for corn, upland rice, paddy rice, tomato and cucumber; 32°C. for wheat; 30°C. for spinach; 29-30°C. for naked barley; 29°C. for barley and radish; and 27°C. for rape. Thus, it was found that the temperature was high in summer crop plants and low in winter ones. 5. The rate of protoplasmic streaming differed with species of plants. In wellwater (pH 6.6) of 20°C., the rate was rapid (6-8μ/sec.) for wheat, barley, naked barley, upland rice and paddy rice; moderate (5-6μ/sec.) for tomato, rape and corn; and slow (4-5μ/sec.) for spinach, radish and cucumber. 6. A slight varietal difference of streaming rate was observed in varieties of rice and wheat plants, but the temperatures for maximum rate did not differ with varieties. 7. The streaming was observed to stop at high temperature, within 40-45°C. with rice plant. The temperature was somewhat higher with the southern rice varieties or summer crop plants than with the northern rice varieties or winter crop plants. 8. Under certain limit of temperature, the streaming stopped at high temperature and recovered after the lowering of temperature, but it failed to recover, if the tempereture exceeded 45°C., with rice plant. 9. The streaming was also observed to stop at low temperature within 0-10°C., with rice plant. 10. When the temperature was lowered to 0--2°C. with rice plant, the streamig recovered as the temperature rose if the water did not freeze and the temperature did not rise suddenly. 11. The rate of streaming in rice plant increased somewhat in dilute solution of H2O2 (0.00003-0.000003%) in wellwater, but in a higher concentration (0.003%) the streaming stopped. 12. The rate in rice plant decreased in dilute H2S solution (0.000009 mol) and in a slightly higher concentration (O.OOO625 mol) the streaming stopped. 13. The rate in rice, wheat and barley plants decreased in dilute solution of KCN (0.0001 mol) in wellwater and in a slightly higher concentration (0.00l mol) the streaming stopped. 14. The rate in rice plant in boiled wellwater decreased after prolonged submersion. 15. The temperature for maximum rate in rice plant was slightly higher in dilute H2O2 solution, but it was lower in wellwater (after prolonged submersion) or in dilute KCN solution. 16. The rates of streaming in the roots which had grown in wellwater or in air (on moist filter paper) were observed respectively. With paddy rice, the rate at high temperature was more rapid in the former than in the latter. With wheat and barley, however, it was more rapid in the latter. With upland rice, the tendency was intermediate. The temperature for maximum rate did not differ between the plants cultured under both conditions. 17. The number of streaming root hairs in rice plant decreased under pH 4.0 and over pH 10.4, in wellwater. The streaming stopped completely at pH 1.4 as the result of coagulation of the protoplasm. At pH 10.5 the protoplasm of all root hairs dissolved. 18. [the rest omitted]