THE EFFECT OF FLASHING LIGHT SUPPLEMENTED BY CONTINUOUS RED AND FAR-RED LIGHT ON THE GROWTH OF LEMNA MINOR L. IN THE PRESENCE OF GROWTH REGULATORS

Abstract

The growth rates of Lemna minor were studied under conditions of flashing light of varied durations interacted with continuous illumination of low-intensity far-red and red light, and growth regulators (0.645 p.p.m. kinetin, and 25 p.p.m. IAA). It was found that the growth rate was progressively reduced with decreasing light exposure from continuous illumination to alternating periods of 1-minute intermittency, after which it increased rapidly. The growth rate per unit of light was the most rapid at 0.01-second light period under 1:3 ratio of light to dark. Under 1:1 ratio of light to dark interacted with red and far-red light, kinetin, and IAA, the photosynthetic rate of Lemna was reduced by far-red but improved by the red light. Kinetin increased the growth rate but IAA inhibited the photosynthetic rate as the number of flashes increased. The IKI test showed that under flashing light old and young fronds stored starch but under continuous illumination, only the older fronds stored starch.