Institute for Agricultural Research, Tohoku University, Sendai 980 Japan.
Plant Physiol. 1979 Jun;63(6):1107-10. doi: 10.1104/pp.63.6.1107.
Phototropic responses of a tip-growing coenocytic alga Vaucheria geminata to intermittent blue light pulses were analyzed. Curvatures caused by repeated light pulses separated by dark intervals of various lengths were as large as those obtained by continuous light of the same incident energy, unless the length of the dark interval exceeded a critical value of about 30 to 40 seconds. If the dark interval was longer than the critical length, bending no longer took place. Another response to intermittent irradiation was found. In a narrow range of light pulse and dark interval lengths, i.e. light pulses longer than 10 milliseconds and dark intervals shorter than a value ranging from 15 to 150 milliseconds, intermittent irradiation was more effective than continuous irradiation of the same total energy. In this region, the maximum response to repeated pulses was equal to the curvature caused by a continuous irradiation of the same total elapsed time. It is evident that in this condition the dark interval is not perceived and the alga responds as if it were in light. The results suggest that two different dark reactions may be involved in the phototropic response of this algal cell.
对共生细胞藻 Vaucheria geminata 的向光性反应进行了分析，该藻的细胞可向光生长。由重复的光脉冲引起的弯曲，其程度与用相同入射能量的连续光照射时一样大，除非暗间隔的长度超过约 30 到 40 秒的临界值。如果暗间隔长于临界长度，则不再发生弯曲。对间歇辐照还发现了另一种响应。在光脉冲和暗间隔长度的较窄范围内，即光脉冲长于 10 毫秒且暗间隔短于 15 至 150 毫秒的范围，间歇辐照比相同总能量的连续辐照更有效。在这个区域，重复脉冲的最大响应等于用相同总持续时间的连续辐照引起的曲率。显然，在这种情况下，暗间隔不会被感知，藻类的反应就好像它在光中一样。结果表明，这种藻类细胞的向光性反应可能涉及两种不同的暗反应。
