Influence of continuous light on the tomato

Abstract

As early, as 1929, Guthrie (2) observed that under continuous light tomato leaves become chlorotic. Later, this "leaf injury"-as the research workers name it - is studied especially in connection with continuous light and invariable temperature. Artur, Guthrie and Newell (1930), Rodenburg (1937), Withrow ( 1949), Highkin and Hanson (1954), Laurence and Calvert (1954), all quoted by 2), showed that low temperatures reduce the negative effect of continous light on the tomato. The same chlorotic aspect of leaves, in conditions mentioned above, is observed by Kristoffersen in his detailed studies relating this problem (2). Kettellapper's experiments have shown that in continuous light, in long photoperiods and in cycles of 48 and 72 hours with a shorter photoperiod than optimum, the chlorotic leaves appear always. All the authors above, reported the "leaf injuty" appearing under continuous light when temperature was invariable. In these conditions, the plants have yellow leaves with necrotic spots, that finally dried. In our experiments relating influence of photoperiod on the tomato, we found at the plants in continuous light a "degeneration" of whole plant, although in conditions in which the night temperature was different from the day's one.